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Wednesday, January 21, 2015

Directed Energy from Navy Site

 
Applications Across Land, Air, and Sea



Challenges & Solutions


for the 21st Century





Volume 7, Issue No. 4


1


Table of Contents Directed Energy

3 Leading Edge Directed-Energy RDT&E





Captain Michael H. Smith



4 Directed-Energy Topics in This Issue





Mr. Dale Sisson



Past, Present, and Future

6 Naval Directed-Energy Weapons —




No Longer a Future Weapon Concept


David C. Stoudt



12 Historical Overview of Directed-Energy Work at Dahlgren





Stuart Moran



26 History of Laser Weapon Research





Melissa Olson



36 Laser Weapon System (LaWS) Adjunct to the Close-In




Weapon System (CIWS)


Robin Staton and Robert Pawlak



RDT&E, Acquisition, and Warfare Management

44 The Acquisition Challenge Associated With Directed-Energy RDT&E





Mike Kotzian



Technology, Modeling, and Assessment

50 The Basics of Electric Weapons and Pulsed-Power Technologies





Stuart Moran



58 Solid Modeling of Directed-Energy Systems





Joseph F. Sharrow



64 A Fundamental Key to Next-Generation Directed-Energy Systems





Directed Energy Division, Electromagnetic and Sensor Systems Department



70 Active Denial Array





Randy Woods and Matthew Ketner



74 Directed Energy in the Military Environment





LT Leedjia Svec, Jeremy Beer, and Dave Freeman



High-Power Microwave

78 Directed Energy Using High-Power Microwave Technology





Jacob Walker and Matthew McQuage



High-Energy Laser

82 Laser Counter Rocket, Artillery, and Mortar (C-RAM) Efforts





Michael Libeau



Nonlethal Capabilities

86 Multifrequency Radio-Frequency (RF) Vehicle Stopper





Stephen A. Merryman



92 High-Power Electrical Vehicle-Stopping Systems





Jordan Chaparro and Melanie Everton



96 Nonlethal Small-Vessel Stopping With High-Power




Microwave Technology


Jacob Walker


Volume 7, Issue No. 4


2


Naval Surface Warfare Center, Dahlgren Division (NSWCDD)


Captain Michael H. Smith, Commander

Carl R. Siel, Jr., Technical Director

David C. Stoudt, Distinguished Engineer for Directed Energy (ST) and




NAVSEA Technical Warrant for Directed Energy and Electric Weapon Systems


Janice Miller, Corporate Communications Director (Acting)

Steve Zehring, Managing Editor

Margie Stevens, Production Coordinator

Patrice Waits, Editor & Layout

Clement Bryant, Layout Design & Graphic Artist

Kellie Yeatman, Graphic Artist

Trey Hamlet, Graphic Artist/3-D Modeling




Electromagnetic & Sensor Systems


Dale Sisson, Head, Q Department

Brandy Anderson, Graphic Artist/Cover Design




NSWCDD


Jordan Chaparro

Melanie Everton

Matthew Ketner

Michael Libeau

Matthew McQuage

Stephen A. Merryman

Stuart Moran

Melissa Olson

Robert Pawlak

Joseph F. Sharrow

Robin Staton

Jacob Walker

Randy Woods

Defense Acquisition University


Mike Kotzian

Naval Medical Research Unit – San Antonio


Jeremy Beer

Dave Freeman

LT Leedjia Svec

The Leading Edge magazine is produced by the Naval Surface Warfare Center, Dahlgren,




Virginia. The purpose of the publication is to showcase technical excellence across the Warfare

Centers and promote a broader awareness of the breadth and depth of knowledge and support

available to the Navy and DoD.


Address all correspondence to Corporate Communications, C6

Email: dlgr_nswc_c6@navy.mil; or write to

Commander

Naval Surface Warfare Center, Dahlgren Division

Corporate Communications, C6

6149 Welsh Road, Suite 239

Dahlgren, VA 22448-5130

NSWCDD/MP-09/34

Approved for public release; distribution is unlimited.

33




Introduction



Leading Edge Directed-Energy RDT&E


Dahlgren first launched research and development efforts devoted

to harnessing the power of electromagnetic energy over

40 years ago. From early work with voltage multipliers and pulsepowered

technology, to today’s high-energy lasers and high-power

microwave technologies, the Naval Surface Warfare Center,

Dahlgren Division (NSWCDD) has led, and continues to lead,

cutting-edge directed-energy research, development, testing, and

evaluation. Our commitment in this area only grows stronger—evidenced by our chartering of the Directed Energy Warfare Office

(DEWO)—n order to provide increased focus on warfighting

applications of these technologies.

Today’s military forces face a wide array of challenges in diverse

operating environments around the world. Directed energy

offers unique and flexible options to address today’s challenges,

as traditional kinetic weapons are often of limited value in peacekeeping

missions and in urban environments, where restricted

rules of engagement typify the norm. Kinetic weapons can also be

more costly or ineffective to employ against asymmetric threats.

The Chief of Naval Operations (CNO) recently placed added

emphasis on directed energy and on expanding the range of directed-

energy capabilities. In response, scientists and engineers at

NSWCDD are actively developing prototype systems in a number

of areas that you will read about in this issue—reas that have

been successfully demonstrated and tested in our Navy laboratories

and ranges.

In this issue of The Leading Edge magazine, you will trace the



rich history of directed-energy work at Dahlgren, gain insight into

directed-energy weapons already fielded or being readied for the

field, and learn about prototypes that show real promise for providing

incredibly effective offensive and defensive directed-energy

solutions. For example, scientists and engineers at NSWCDD

are leading the way toward realizing small, lightweight radio frequency

(RF) transmitters using high-power, solid-state switching

amplifiers for the development of counter-improvised explosive

device detection and neutralization systems. You will also learn

about diverse applications of directed-energy technology—such

as research and testing of laser glare devices and laser eye protection—

and have the opportunity to gain a better understanding of

the Department of Defense (DoD) acquisition framework and the

challenge of maintaining cost and schedule estimates while delivering

weapons systems that are critical to the warfighter.

From lasers to high-power electrical vehicle-stopping systems,

I am sure you will be fascinated and, along with me, be impressed

with the advancements our scientists, engineers, and technical

staff are achieving in the directed-energy arena to support of our

men and women in uniform.

Captain Michael H. Smith, USN


Commander, NSWCDD


4



Welcome to our Directed Energy issue of the Leading Edge



magazine. This issue represents the third in a trilogy of issues

covering the truly fascinating and incredibly challenging area

of naval warfare in the operational electromagnetic environment.

In our first issue, we covered the full range of operational

and readiness implications when operating in the electromagnetic

environment. Then, in our second issue, we highlighted

the complexities and dynamics of providing relevant and effective

sensors and radars to our warfighters. Now, we focus on

directed energy and relate how the Naval Sea Systems Command

(NAVSEA) Warfare Centers, and the Naval Surface Warfare

Center, Dahlgren Division’s (NSWCDD’s), in particular,

are working on state-of-the-art directed-energy weapons capabilities

for the warfighter.

In this issue, we first look back to the early years, decades

ago, when directed-energy weapons research began. We examine

the history of directed energy, and we cover significant discoveries

and achievements made by NAVSEA Warfare Center

scientists and engineers, and others in the scientific community.

We then relate information about several of our current directed-

energy initiatives, and about how we’re working hard to

solve some of the most complex technical challenges associated

with directed-energy weapons. We highlight how others in

the Navy, such as the Naval Medical Research Unit in San Antonio,

Texas, are also conducting research into directed energy

and how our forces can better protect themselves from the

effects of directed energy. We show how directed energy can

be employed in a variety of offensive and defensive, lethal and

nonlethal situations. We explain how directed-energy weapons

work and how they can be employed in various environments

against a wide range of situations. Lastly, we look forward as we

provide technical and strategic leadership for the efficient and

effective development, acquisition, and fielding of directed-energy

systems for the warfighter.

So, if you want to learn about what the NAVSEA Warfare

Centers and others in the Navy are doing in the area of directedenergy

weapons, look no further than this issue of the Leading

Edge magazine. I’m confident that you will be impressed by the



progress made in this most important technology field.

Dale Sisson


Head, Electromagnetic and

Sensor Systems Department

NSWCDD Dahlgren, Virginia



Directed-Energy Topics in This Issue


5

6


Directed Energy


Past, Present, and Future



Naval Directed-Energy Weapons —

No Longer A Future Weapon Concept


By David C. Stoudt



Directed-energy weapon (DEW) technologies typically take the form of highenergy

lasers (HELs), high-power microwaves (HPMs), and charged-particle beams.

This article focuses on the first two technology areas, as they have reached the point of

being ready for operational testing and evaluation, and in some cases, operational use

on the battlefield. DEWs have been popularized in science-fiction writings for over a

hundred years. The Department of Defense (DoD) has been investing in their development

since the 1970s. This article will not go into technical depth regarding the various

directed-energy (DE)-related efforts currently underway in the Navy, but rather, it will

overview DE areas under development and relate recent Navy leadership activity. Other


articles in this issue of The Leading Edge magazine will provide the reader with much




greater technical and programmatic details on various DE efforts.


High-Energy Laser Weapons

HEL weapon systems have been envisioned for a great many years, to include being


referred to as Martian “Heat Ray” weapons in H.G. Wells’ epic novel The War of the

Worlds, originally published in 1898. In reality, a high-average-power laser weapon system




is very similar to a “heat ray”, or even a blow torch. During the early years of DoD

investments in DE technology, the Navy led the development of HEL with the creation

of the world’s first megawatt-class, continuous-wave, Mid-Infrared Advanced Chemical

Laser (MIRACL), located at White Sands Missile Range (WSMR). Roughly 80 years

after the work of H.G. Wells, the U.S. Navy tested the MIRACL laser and ultimately

used that laser system to engage static and aerial targets in the desert of WSMR in the

following years. While that laser proved to be the wrong choice for the Surface Navy’s

self-defense mission, it did spawn work by the Air Force on the Airborne Laser (ABL),

and the Army on the Tactical High-Energy Laser (THEL). In 2000 and 2001, the THEL

successfully shot down 28 supersonic Katyusha artillery rockets and 5 artillery shells.


Dr. Stoudt is the Distinguished Engineer for Directed Energy (ST)

and the NAVSEA Technical Warrant for Directed Energy and Electric

Weapon Systems.


7


Naval Directed-Energy Weapons —

No Longer A Future Weapon Concept


In 2010, the ABL successfully engaged and destroyed

tactical ballistic missiles during the boost

phase of their flight. All three of these laser systems—

the MIRACL, the ABL, and the THEL—

are chemical lasers that utilize toxic chemicals

and operate in less than optimal wavelengths that

make them a poor choice for most naval applications.

The MIRACL is shown in Figure 1.

Recent advances in solid-state lasers, to include

fiber lasers, have moved these electric lasers

to the forefront of the Department’s research

and development (R&D) for near-term HEL applications

in the services. The Navy has particular

interest in electric lasers, to include the free-electron

laser (FEL), for shipboard self-defense and

force protection applications. The speed-of-light

delivery of HEL energy can defeat the high-g maneuvers

of newly developed foreign antiship

cruise missiles (ASCMs). Thus, the Office of Naval

Research (ONR) started an FEL Innovative Naval

Prototype (INP) program in FY10, with a goal of

reaching the output power of 100 kW. The eventual

goal of the FEL program is to reach the multimegawatt

power level with wavelength selectivity.

The Naval Sea Systems Command (NAVSEA) Directed

Energy and Electric Weapons Program

Office (PMS 405) has been actively developing a

fiber laser-based Laser Weapon System (LaWS)

that could be a retrofit to augment the current capabilities

of the Close-In Weapon System (CIWS)

currently deployed on many surface combatants.

The Naval Surface Warfare Center, Dahlgren Division

(NSWCDD), is the Technical Direction

Agent and lead system integrator for PMS 405 on

the LaWS program. The Naval Air Systems Command

(NAVAIR) has interest in compact, solidstate

HEL systems for aircraft self-protect and

air-to-ground engagements, and will be starting a

Figure 1. Mid-Infrared Advanced Chemical Laser (MIRACL)




8

Directed Energy


Past, Present, and Future



Figure 2. Laser Weapon System (LaWS)



fiber laser-based ONR Future Naval Capability effort

in FY12. LaWS is shown in Figure 2.

High-Power Microwave Weapons

Like lasers, microwave weapons have been fantasized

about ever since the invention of microwave

power generators. In fact, in 1932 it was generally

recognized by the British government that bombers,

ostensibly German bombers, would be able to

penetrate British air space and bomb its civilian

population and infrastructures. In 1934, the Air

Ministry initially asked Robert Watson-Watt, of

the National Physical Laboratory, if he could build

a “death ray” that could kill enemy pilots or detonate

bombs while they are still on the planes of enemy

aircraft. Such a “death ray” had been proposed

to the Air Ministry by Harry Gindell-Mathews

10 years earlier in 1924. Watson-Watt, a former

meteorologist who had become an expert on radio

signals, suggested that energy reflected from an

aircraft could be used to locate it. His experiments

were successful and RADAR (radio detection and

ranging), a name coined by the U.S. Navy in 1940,

was born. While RADAR is not a DEW in the way

they are thought of today, its roots can clearly be

traced to the military’s desire for such capabilities.

The Navy’s HPM, or high-power radio-frequency

(RF) systems, have been progressively increasing

in power density to the point where it is now feasible

to integrate the technology into weapon systems

for deployment. While initial HPM applications

suffered from their inability to obtain militarily

useful outcomes, either due to technology limitations,

difficult concept of operations (CONOPS),

or inherent robustness of potential target systems,

many feasible military applications for using HPM

9


Naval Directed-Energy Weapons —

No Longer A Future Weapon Concept


Figure 3. Multifrequency RF Vehicle-Stopper (RFVS) System



devices have surfaced over recent years to include

nonlethal, antipersonnel weapons and nonkinetic,

antimateriel weapons. While these concepts offer

unique capabilities to the warfighter

due to the

nonkinetic effects they generate, other warfighting

concepts—such as stopping vehicles, or countering

hidden roadside bombs or improvised explosive devices

(IEDs)—are difficult to achieve by any other

means. The multifrequency Radio-Frequency Vehicle

Stopper (RFVS) system is shown in Figure 3.

In addition, the difficulty in overcoming the

propagation losses associated with HPM has driven

some concepts into platforms such as unmanned

aerial vehicles (UAVs) or cruise missiles

that deliver the HPM device to the target for a

close-in engagement. Over the past 10 years, fieldtestable

prototypes have been developed to demonstrate

the operational utility of these concepts,

and in some cases, those prototypes have or will

be deployed operationally to support our troops in

theater. It is only through the hard work and perseverance

of the Naval Research Enterprise (NRE), as

well as other DoD laboratories, that concepts that

were once only laboratory curiosities are now making

their way onto the battlefield and contributing

to the fight.

Foreign Directed-Energy Weapon

(DEW) Development

While the United States has been very active in

this warfighting

area, significant foreign DEW development

also has elevated the need for the Navy

to afford these threats a higher priority. This can be

done either by incorporating the necessary DEW

countermeasures into weapon systems, platforms,

and critical infrastructures, or by adapting the

CONOPS and tactics, techniques, and procedures

(TTPs) employed by our armed forces to properly

account for those foreign DEW systems. Materiel

developers need to understand how this threat

10

Directed Energy


Past, Present, and Future



is evolving and properly address it during the design

of their systems. They also need to address DE

in the development of their system threat assessments.

There has been movement on the HPM side

to modify existing military standards, such as MIL

STD 4641 and others, to now include information



on potential HPM threats. For example, in the HEL

arena, work has been accomplished in the development

of protective measures for eyes; however, this

threat needs to be considered during the system

development process. It is well known that building

in countermeasures is much cheaper during

the initial development of a system, vice trying to

retrofit systems with countermeasures once a new

threat is on the battlefield. As analysts evaluate the

foreign development of DE technologies, and the

trends become clearer, it is the responsibility of the

acquisition community to take this threat into consideration

and ensure that weapon systems, platforms,

and infrastructures will be available and

at full capability when needed. By accounting for

foreign threat developments, assessing blue force

susceptibilities and vulnerabilities, and adopting

appropriate measures to negate or counter these

threats, naval forces will avoid technological surprise

on the battlefield in the future.

Requirements

The DE programs briefly mentioned in this

article, and covered more deeply in this and other

publications, offer warfighters unique capabilities

not currently found in their arsenal. The

continuing problem, however, is matching those

unique capabilities to vetted operational requirements.

The DE technical community has made

great strides in helping the operational community

understand the capabilities of DE weapons and

their potential military effects on targets. The lack

of formal requirements, however, has yielded more

of a technology push—rather than an operational

pull—of various DE capabilities. Progress has been

made, but more effort is required if DE capabilities

are to be developed and transitioned between science

and technology (S&T), and formal programs

of record. Notwithstanding, the current outlook

and trends are positive.

A Resurgence of Navy Interest in

Directed Energy

The Navy’s interest in DEWs for future maritime

operations has increased in recent years due

to a number of weapons development successes.

Recognizing the importance and value of DEWs,

NAVSEA reestablished the Navy Directed Energy

Weapons Program Office (PMS 405) in 2004.

Accordingly, PMS 405 was designated as the point

of contact for matters related to DE and electric

weapon systems (EWS) development and acquisition

initiation for NAVSEA, and for matters

being coordinated with other federal agencies and

military services. PMS 405’s mission is to transition

technology from the laboratory to prototype/

advanced development/testing for operational development

and use.2, 3



The Navy also established its first formal executive

position for DE (ST-level), the Navy’s Distinguished

Engineer/Scientist for Directed Energy,

at NSWCDD in August 2004. Following the establishment

of this position, NAVSEA then formally

established a Technical Authority Warrant

for Directed Energy and Electric Weapon Systems

(DE&EWS)—urface Ships in July 2008. The scope

of the warrant includes the transition of S&T development

to weapon system development of lethal

and nonlethal capabilities associated with the

DE&EWS for Surface Ships.4 This included, but



was not limited to, the following:

Laser Weapon Systems



◆◆High-Energy Lasers

◆◆ Solid-State Lasers

◆◆Free-Electron Lasers

◆◆Femtosecond Ultrashort Pulse Lasers

◆◆Laser-Induced Plasma Channel

◆◆Lethality/Vulnerability

Electromagnetic Rail Gun Weapon System

High-Power Microwave



◆◆Active Denial System

◆◆Laser-Guided Energy

Maritime Directed Energy Test Center

Electromagnetic Launch of Weapons (excluding



the Electromagnetic Aircraft Launch

System (EMALS))

Then, within the NAVSEA Warfare Center Enterprise,

Warfare Center leadership established two

technical capabilities (TCs): an NSWCDD TC for

DE systems research, development, test, and evaluation

(RDT&E); and a Naval Surface Warfare Center,

Port Hueneme Division (NSWCPHD) TC for

in-service engineering, test and evaluation (T&E),

and integrated logistics support to DE systems.

NSWCDD leads all S&T and RDT&E for the development

and weaponization of DE systems for surface,

air, and ground environments. It also leads the

development of offensive and defensive DE technologies

needed to characterize and exploit vulnerabilities,

provide weapons, and protect against attack.

NSWCDD provides the technologies, devices, and

systems designed to create or control electromagnetic

energy used to cause persistent disruption or

permanent damage by attacking target materials,

11


Naval Directed-Energy Weapons —

No Longer A Future Weapon Concept


electronics, optics, antennas, sensors, arrays, and

personnel, including nonlethal applications. NSWCPHD

provides in-service engineering, T&E, and

integrated logistics support to DE systems throughout

the system life cycle.

The Navy further demonstrated increased

interest in DE when Assistant Secretary of the

Navy (Research, Development & Acquisition

(ASN(RDA)) designated NAVAIR offensive and

defensive leads for naval aviation DE activities:

Program Executive Officer for Unmanned



Aviation and Strike Weapons (PEO(U&W)),

assigned as the offensive DE lead for naval

aviation

PEO for Tactical Aircraft Programs (T), assigned



as the defensive lead for naval aviation

Concerning future initiatives, the Chief of Naval

Operations (CNO) tasked the Strategic Studies

Group (SSG) to examine a topic entitled “Maritime

Operations in the Age of Hypersonic and Directed-

Energy Weapons.”5 The intent of the study



was to provide Navy leadership with an understanding

of where DE technologies and weapons

are today and how they might influence future

maritime operations. The theme of the study was

completed during FY10, the results of which discuss

many DE concepts, as well as tactics for the

employment of DE capabilities. The study’s findings

are currently under review and consideration

by senior Navy leadership.

Conclusion

While H.G. Wells’ The War of the Worlds novel

and television programs like Star Trek popularized



the notion of using DE for weapons in years

past, today— through persistent DEW RDT&E—

Navy leadership is realizing the great potential that

DEWs offer naval warfighters and homeland defenders.

The scientific and technical advances the

Navy has made in HEL and HPM in recent years

have been nothing short of extraordinary. Moreover,

future technological and engineering advances

undoubtedly will result in profound differences

in our nation’s future warfighting capabilities. Naval

DEWs, therefore, are no longer just a future

weapon concept…they are here today.

References

1. Department of Defense Interface Standard, Electromagnetic Environmental

Effects—Requirements for Systems, MIL-STD-464, 18



March 1997.

2. NAVSEA Notice 5400, Ser 09B/240, Subject: Establishment of the

Navy Directed Energy Weapons Program Office (PMS 405), dated

4 January 2002.

3. NAVSEA Instruction 5400.101, Ser SEA 06/058, Subject: Directed

Energy and Electric Weapons Program Office (PMS 405) Charter,

dated 21 July 2004.

4. NAVSEANOTE 5400 Ser 09B/240 of 4 January 2002 and

NAVSEAINST 5400.101 Ser SEA 06/058 of 21 July 2004.

5. Letter from the CNO tasking the SSG XXIX Theme—”Maritime

Operations in the Age of Hypersonic and Directed-Energy Weapons,”

dated 23 September 2009.

12


Directed Energy


Past, Present, and Future



Historical Overview of

Directed-Energy Work at Dahlgren


By Stuart Moran



In 1962, the United States set off a megaton nuclear weapon 250 miles above the

Pacific. The blast caused a large imbalance of electrons in the upper atmosphere that

interacted with the Earth’s magnetic field to create oscillating electric fields over a large

area of the Pacific. These fields were strong enough to damage electronics in Hawaii, a

thousand miles away, and clearly demonstrated the effects of an electromagnetic pulse

(EMP). It didn’t take long for the military to begin considering ways to create such

pulses without using nuclear weapons.

In the late 1960s, the Special Applications Branch at the Naval Weapons Laboratory

at Dahlgren began studying ways to generate high-power oscillating electric fields that

could be used as a weapon to damage enemy electronics. These devices were basically

high-power versions of the old spark-gap transmitters used in the early days of radio.

To construct a device that could produce nuclear EMP-like fields, stored electrical energy

was converted to radio-frequency (RF) energy that could be radiated from an antenna

through the atmosphere to a target. These devices typically would store energy in

a high-voltage capacitor and release the energy quickly using a spark-gap switch. This

would then drive oscillating currents on an antenna, causing it to radiate. To achieve

field strengths of thousands of volts per meter, typical of a nuclear EMP, devices operating

at hundreds of thousands of volts or more were needed.

A number of radiating devices were studied in the early 1970s. Most belonged to a

class of devices called Hertzian oscillators. A capacitor is charged to high voltage, the

switch is closed, and current flows in the circuit, causing the stored energy to oscillate

between the electric field of the capacitor and the magnetic field of the inductor.

To charge the capacitor to extremely high voltages, a step-up transformer of some type

must be used. One of the fastest voltage multipliers, the Marx generator, was frequently

used. The losses from internal resistance and external radiation damp the oscillating

waveform, typically after a few cycles. The radiated pulses are, therefore, short in


time and broad in frequency content.1 A simple diagram of the inductance-capacitance




oscillator (L-C oscillator) is shown in Figure 1.


Single-Pulse Burnout Devices

Many types of Hertzian devices were designed, constructed, and tested at Dahlgren during

the 1970s. The transmission-line oscillator, or cavity oscillator, used a quarter-wavelength


13


Historical Overview of

Directed-Energy Work at Dahlgren


coaxial pipe, which was switched at one end, to create

the oscillating waveform. A frozen wave generator,

a different type, had quarter-wave sections of cable

that were charged plus and minus to create a twocycle

waveform “frozen” in the cable. All sections

were simultaneously switched, causing the wave to

travel to an antenna. A special folded design was developed

so one switch could be used, eliminating

the multiswitch synchronization problem. A Ross

circuit used a square wave pulse, which traveled

down cable “tees,” creating reflections, which were

timed to create several RF cycles. In the Travetron,

the turn-on time of a series of spark-gap switches

was incorporated as a designed delay, creating

reflections through a series of gaps to produce the

waveform. This design allowed higher frequencies.

All of these devices were designed, built, and tested

to determine power and frequency capabilities,

as well as efficiency.

Scientists and engineers at Dahlgren built and

tested versions of Hertzian oscillators operating up

to half a million volts. These devices powered relatively

simple monopole or dipole antennas that

could produce very high electric fields at hundreds

of meters. In the early 1970s, a special outdoor

field-measurement range was constructed.

It housed high-voltage systems in underground

trailers that fed antennas above ground on a specially-

built, 100-m-long ground plane that was

constructed for testing and field measurements. A

picture of the ground place in a fielded measurement

range is shown in Figure 2. Field probes were

even carried aboard helicopters to make measurements

above ground effects, as shown in Figure 3.

Other types of devices to produce pulses were

constructed, too. Vector inversion generators used

spiral-wound capacitive plates to generate high

voltages without transformers.2, 3 The Landecker



ring used a paddle-wheel arrangement of capacitors

and inductors charged in parallel and discharged

in series. The circular arrangement was

designed so the entire system would radiate as a

magnetic dipole, thus forming its own antenna.4



Switch timing was critical, and Dahlgren engineers

attempted to verify reports that Landecker developed

a specific type that brought all capacitor leads

into a single-center spark gap.

Scientists and engineers also looked at devices

that used explosives to generate the electrical energy

needed. These included explosive flux compressors

of several types, which generated fields and then explosively

squeezed the fields between conductors to

amplify the peak power. In the early 1970s, a large

(70-ft clear zone) anechoic chamber was constructed

at Dahlgren with an explosive chamber in one

end. Explosives would be set off in the chamber to

drive various types of flux compressor schemes that

would generate electrical pulses fed into an oscillator

and antenna in the anechoic chamber. Pulse parameters

and field strengths could be measured. Impedance-

matching networks, matching transformers,

and methods of improving efficiency were studied.

Tests were performed at Dahlgren and at Los Alamos

using large antennas suspended from balloons.5



In other schemes, piezoelectric devices were developed,

which could be compressed hydraulically and

then quickly released to produce high voltages. The

concept was to use explosives to generate the high

Figure 1. Inductance-Capacitance Oscillator (L-C Oscillator) Diagram




14

Directed Energy


Past, Present, and Future



Figure 2. Field Measurement Range

Figure 3. Airborne Electric Field Measurements




15


Historical Overview of

Directed-Energy Work at Dahlgren


pressures. Ferroelectric and ferromagnetic transducers

driven by explosives were also tested.6



Special Effects Warhead

(SEW) Program

In 1973, Dahlgren began the SEW Program to

look at the feasibility of “burning out” enemy radar

and missile systems using single-shot, very highpeak-

power EMPs. The program looked at the

feasibility of constructing an electromagnetic warhead

that could disable electronics beyond a normal

hard-kill explosive range as far as a mile away.

The program was funded at several million dollars

a year through most of the 1970s.

A major thrust of the SEW Program was to

better understand the effects of high fields on military

electronics. Little information was available

on the vulnerability of foreign or U.S. electronics,

particularly entire systems. A trailer-based RF impulse

system, employing a Marx-driven L-C oscillator

charged at two million volts, was constructed

at Dahlgren. This Transportable Oscillating Pulser

System (TOPS) was connected to a large boundedwave

structure that produced uniform fields over a

region large enough to place an entire radar or missile

system. The electric field emitted from the throat

of this system was so high that a special bag of highvoltage

gas was needed until the radiating structure

became large enough to transition to the normal atmosphere.

A picture of TOPS is shown in Figure 4.

Since many important target systems were not

available for testing, much of the vulnerability information

was obtained from U.S. electronics, and

estimates were then made for foreign systems. In

addition to the tests done at Dahlgren, pulsers were

also constructed in mobile trailers that could be

transported to other sites for testing against simulated

or actual targets. The Mobile Oscillating Pulser

System (MOPS) was an example that was carried

to test sites, such as China Lake, to perform tests

against radars and simulated foreign systems.

A key requirement for the SEW Program was

to demonstrate enforceable target vulnerability,

which means that a high percentage of the time a

large percentage of the targets are affected. One important

finding was the broad difference between

an electromagnetic safety concern—here a 1 percent

vulnerability was far too great—nd a weapon

concern—here a 10 percent vulnerability was

not good enough. The field strengths between the

safety requirements and weapon requirements often

were many orders of magnitude apart.

The SEW Program looked at many types of

electronic component vulnerability, subsystem

vulnerability, and complete system vulnerability.

As a result, energy tables for burnout effects were

developed. Subsequently, Dahlgren performed numerous

field tests against radar and communications

systems between 1973 and 1978, and funded

component and subsystem testing on missiles.

Figure 4. Transportable Oscillating Pulser System (TOPS)




16

Directed Energy


Past, Present, and Future



Repetitive Systems for

Electronic Warfare

The electric fields required to damage military

electronics in the 1970s often were very high, and

ranges typically were limited. As a spinoff of programs

trying to damage targets with a single pulse,

some of these devices were reduced in size and

power, and operated in a repetitive mode to generate

noise pulses for the purpose of electronically

jamming target systems. In 1976, the Naval Air

Systems Command (NAVAIR) began the Electromagnetic

Countermeasures Program to study the

application of high-repetition-rate Hertzian devices

for use as noise jammers. The initial targets were

low-frequency radars.

In late 1976, Dahlgren performed effectiveness

tests against various radars using helicopter-mounted

Hertzian jammers. These devices were able to

screen incoming target aircraft at useful ranges. The

concept of a forward-launched rocket to deliver a

parachute-suspended Hertzian jammer also was investigated.

Dahlgren teamed with engineers at China

Lake to study packaging concepts of utilizing an

extended 5-inch Zuni rocket as a forward-fired delivery

vehicle. A prototype is shown in Figure 5.

Similar Hertzian devices were considered for

use as communications and data-link jammers.

Several antenna deployment schemes were developed,

and by fall 1978, successful ground launches

had been performed in which the deployment sequence

and jammer operation were demonstrated.

The name Zuni Expendable Pulsed-Power Oscillator

(ZEPPO) was given to the project. Dahlgren

teamed with the Naval Avionics Center (NAC) to

build the systems. By 1980, China Lake fired the

first air-launched prototypes at both low and high

altitudes. Devices, batteries, spark gaps, and antennas

continued to be developed, and new targets—

such as spread-spectrum systems—were tested.

Other delivery systems besides rockets were also

considered.

The Pulsed Power

Technology Program

Large directed-energy weapons (DEWs) often

required megawatts or gigawatts of peak power,

so methods of supplying and modifying this power

were needed. As Dahlgren became involved in a

broad range of DEW systems, one attribute became

more and more obvious: the size, weight, and cost of

a directed-energy (DE) system were dominated by

the pulsed-power technologies needed to drive the

system, not by the source device itself. Consequently,

more effort began to be devoted to the power-delivery

technologies needed for many of the weapon

concepts. Pulsed-power components enabled energy

to be stored over long periods of time (seconds)

and released very quickly (nanoseconds) to obtain

a billion times increase in peak power.

Dahlgren hosted a pulsed-power systems

symposium and workshop in 1976 and helped

initiate the International Pulsed Power Conferences,

which began in 1977 and continues today

under the Institute of Electrical and Electronics

Engineers (IEEE). As Dahlgren’s involvement

with systems design increased, it became apparent

that new technologies were needed in the primepower

and pulsed-power area to support a variety

of new concepts. Dahlgren urged the Navy to

initiate a Pulsed Power Technology Program to

develop power sources, energy storage systems,

high-power switches, and power conditioning systems

needed for a variety of future weapons. This

program was initiated in 1978 and was originally

funded by NAVAIR and then by the Directed Energy

Program Office (PMS 405) in the early 1980s.

In addition to the Pulsed Power Technology Program,

PMS 405 also began funding free-electron

lasers (FELs), chemical lasers, high-power microwaves

(HPMs), and charged-particle beams

(CPBs). The Pulsed Power Technology Program at

Dahlgren, in turn, funded many areas of research,

both internal and external, over the next 10 years.

Dahlgren served as the focal point for the Navy’s

science and technology (S&T) in pulsed power

and funded many universities, government laboratories,

and commercial companies under the

Pulsed Power Figure 5. ZEPPO Payload Technology Program.




17


Historical Overview of

Directed-Energy Work at Dahlgren


To provide large amounts of electrical prime

power, new types of rotating machines were studied,

including flywheels, conventional alternators,

homopolar generators, rotary flux compressors,

and compensated pulsed alternators. These machines

attempted to produce fast, high-power pulses

using special materials to reduce losses, eddy

currents, and mechanical stresses. MHD generators

were developed using rocket-motor propellant

that could be started and stopped. In the mid-

1980s, a full-scale hybrid (solid fuel/liquid oxidizer)

combustor was fabricated and tested at 10 MW,

achieving world records for power-to-weight ratio

and conductivity. By 1980, new types of energy

storage systems were studied, including inductive

storage and advanced capacitors using new types

of insulating materials and geometries. During the

late 1980s, programs such as the Mile-Run Capacitor

Program reduced the capacitor size by a factor

of 10 through better synthesis of polymer films.

Beginning with internal independent research

funds, Dahlgren developed liquid dielectric materials

based on water/glycol mixtures at low temperatures.

These water-capacitor devices could

hold energy for orders-of-magnitude longer time

periods than ever before, allowing pulseforming

lines to be constructed that could be charged directly

from rotating machines. Dahlgren scientists

developed a world-record high-voltage water

capacitor that could hold pulses for milliseconds

and became internationally recognized experts in

water breakdown.7, 8



High-power fast switching was another important

area of research. Dahlgren funded companies

to develop new types of multistage thyratrons that

could operate at very high voltages. By the early

1980s, multistage thyratrons capable of operating

at over 200 kV, 40 kA with 20 nsec risetimes were

demonstrated. Vacuum switches, ignitrons, plasma

pinch switches, pseudospark switches, backlighted

thyratrons, and e-beam switches all were

studied, as well as a variety of spark-gap switches.

Higher power solid-state switches were developed,

too, using new geometries and substrate material.

Superconducting coils were considered, both

for energy storage and as opening switches. Dahlgren

engineers developed exploding-wire opening

switches, and several types of plasma pinch switches

were funded. They also worked on stacked cable

pulsers. Additionally, concepts for electromagnetic

armor were developed. These systems used

high-density capacitors to blunt penetrators. Inductive

energy storage—which could be far denser

than capacitors—was studied, including methods

of generating the seed current and the problematic

high-voltage opening switch. Opening switches—

which were needed for inductive energy store systems—

were studied, as well as magnetic switches,

which used saturating magnetic material to sharpen

pulses. Magnetic switches operating at 10 kHz

were demonstrated by 1983.9



In 1985, Dahlgren used internal funds to upgrade

a facility to provide controls, diagnostics, and

200 kW of average power at 50 kV to accommodate

testing of new switches and water-based capacitors.

This facility could control the power with a vacuum-

tube pulser and could generate over a million

volts with a rep-rated Marx generator. The facility

was used to:

Develop water-dielectric energy storage, reprated



spark gaps, and pseudospark switches.

Test a variety of switches developed by contractors,

such as back-lighted thyratrons.10, 11



A picture of one system being tested—a water pulseforming

line and spark-gap switch—is shown in

Figure 6.

Dahlgren concentrated in-house switching efforts

in spark gaps. New types of gases were studied,

as well as electrode materials, gas-flows, switch

geometries, and triggering techniques to produce

high-repetition-rate switches for electronic warfare,

as well as particle-beam weapons.12 Dahlgren



scientists and engineers demonstrated 100-μs recovery

of spark-gap switches after handling kilojoules

of energy at hundreds of kilovolts, a world

record.13 The High Energy 2-Pulse System for fast



recovery experiment is shown in Figure 7.

In 1986, Dahlgren ran a workshop on highpower

switching for Navy tactical and Department

of Defense (DoD) strategic applications and

became involved with numerous DoD working

groups on electromagnetic propulsion, high-power

diagnostics, advanced energy conversion, power

modulators, and pulsed power. Spark gaps were

investigated to create underwater noise for submarines.

Dahlgren also led four North Atlantic Treaty

Organization (NATO) Advanced Study Institutes

in Europe and the UK on various pulsed-power

topics. International assessments of key pulsedpower

technologies were also performed.

Particle-Beam Weapons

Particle-beam weapons were a major focus of

DE work during the 1970s and 1980s. A CPB weapon

takes subatomic particles, generally electrons,

and accelerates them to near the speed of light before

sending them toward a target. These fast electrons

penetrate deeply into most materials, so they

are difficult to counter. The high-current electron

beam was to be accelerated by an induction-type

18

Directed Energy


Past, Present, and Future



Figure 6. A Water Pulse-Forming Line and Spark-Gap Switch Test

Figure 7. High Energy 2-Pulse System




19


Historical Overview of

Directed-Energy Work at Dahlgren


accelerator, repetitively pulsed. High electronbeam

currents (kiloamps) and a hole-boring series

of pulses were anticipated to create a stable, longrange

beam. Since the beam was capable of penetrating

quickly and deeply into any target material,

it had the potential to damage electronics and set

off explosives before salvage fuzing could occur.

The beam was predicted to be all-weather and essentially

countermeasure-proof. Even a near miss

could cause substantial damage from high fields

and X-rays produced by the deceleration of electrons

as they hit air molecules near the target. The

CPB concept is shown in Figure 8.

Scientists and engineers from Dahlgren worked

on the pulsed-power technologies needed to drive

these machines beginning in 1980, and it became

a major focus of the Pulsed Power Technology

Program.14 The White Oak Laboratory developed



beam-steering concepts and looked at material interactions.

By 1989, the program investigated:

Propagation

Compact Recirculating Accelerators

Pointing and Tracking

Prime Power

Material Interaction

Fratricide



For a compact shipboard system, recirculating

accelerators were needed to make multiple passes

of the electron beam past the accelerating cavities.

This required a high-power, fast recovery switch,

which Dahlgren began working on in 1988. Using

patented hydrogen switches and special triggering

techniques—efforts that had begun with internal

research funds—Dahlgren demonstrated sparkgap

switches, the only technology that could meet

the current, voltage, and recovery requirements at

that time.15 The High-Voltage 5-Pulse System experiment



is shown in Figure 9.

During these technology efforts, significant

advances were achieved in all aspects of the program.

These included:

Generating high-current, high-energy beams



(although still below weapons parameters)

Demonstrating a 360o turn in a high-current



beam

Propagating a single pulse through the air

Demonstrating beam steering on a small scale

Performing target interaction measurements



Multipulse, long-range propagation was never

demonstrated. A comprehensive tri-service summary

called the Net Technical Assessment for CPB

was sponsored by the Defense Advanced Research

Projects Agency (DARPA) in 1987 to describe the

accomplishments of the program. The report said

compact accelerators were the most pressing technology

need. As a result, most funding was directed

toward this topic. Funding was stopped in

the early 1990s, however, due to the high expense,

stretched timelines, and changes in the threat.

Pulsed Power and

Electromagnetic Launchers

During the 1980s, the Army and Air Force

looked at short-range electromagnetic weapons

to penetrate stronger armor with higher velocities.

The Navy worked on concepts for a weapon

that could be mounted on ships to intercept missile

systems at line-of-sight distances. The Navy—then

the biggest user of space systems—was also interested

in studies showing that small satellites could

Figure 8. Charged-Particle Beam (CPB) Concept




20

Directed Energy


Past, Present, and Future



be electromagnetically launched into low Earth orbit

for the fraction of the cost for a normal launch.

Through the 1980s, electric guns were funded

by independent research and independent exploratory

development programs at Dahlgren, studying

electric gun concepts for both rail guns and

electrothermal (ET) guns. Kinetic energy weapons

were also investigated as part of the Pulsed Power

Technology Program. Under these programs, pure

electric launchers were developed and tested at

Dahlgren, including ones that self-formed projectiles.

16–18 Also studied were ET guns that used the



discharge of electrical energy at the gun breech to

generate a plasma jet. This plasma jet heated a lowmolecular-

weight working fluid, such as water, to

produce a heated gas that accelerated the projectile

to higher velocities than conventional explosives.

The Electrothermal-Chemical (ETC) Gun concept

augmented the electrical energy generating

the plasma jet with a chemical reaction. A 127mm

ETC gun was investigated, and a 60mm ETC gun

was tested at Dahlgren, with the ability to fire short

bursts at a rate of 100 rounds per minute.19



Early Dahlgren work on electromagnetic

launchers—along with capacitor development and

switch advances from the Pulsed Power Technology

Program—allowed Dahlgren to provide the

Navy with detailed conceptual designs in the late

1990s for near-term, long-range rail guns based on

capacitor energy store. These efforts helped support

the decision to begin a long-range rail-gun

program at Dahlgren that continues today, resulting

in world-record achievements. Capital investment

funds were used to construct a high-energy

facility in 2005 to test pulsed-power components

and module designs for use in electromagnetic

launcher programs. An early electromagnetic

launcher is shown in Figure 10.

High-Energy Lasers (HELs)

In general, megawatts of continuous laser

power are required to kill hard targets at long ranges.

Laser technologies that can produce this much

power are very limited. The Navy was a leader in

developing powerful chemical lasers in the 1970s

and 80s. These lasers burned chemical reactants to

Figure 9. High-Voltage 5-Pulse System Experiment




21


Historical Overview of

Directed-Energy Work at Dahlgren


generate the excited states for lasing, thus reducing

the need for large amounts of electrical power.

The Navy built an entire HEL system, including

the Mid-Infrared Advanced Chemical Laser

(MIRACL) and the Sea-Lite beam director. By

1990, this building-sized system demonstrated

shooting boosters, missiles in flight, and supersonic

vehicles. However, the system had drawbacks

because it:

Used hazardous, expensive chemicals

Had propagation problems at the midinfrared



wavelength

Was large in size and high in cost



FELs require electron accelerators similar to

CPB weapons, so they also are large and complex.

However, they can be designed to operate at optimum

wavelengths and scale nicely to higher powers.

The Strategic Defense Initiative began working

on FELs in the late 1980s, funding the advanced

test accelerator at LLNL, originally developed for

CPBs. FELs were also studied under the Strategic

Defense Initiative Organization (SDIO) to be used

as an antisatellite weapon. These lasers went from

milliwatts to watts under SDIO, and then to kilowatts

more recently with work at the Thomas Jefferson

National Accelerator Facility in Virginia.

Space-based lasers and relay mirror systems were

studied under SDIO funding, too, including the

development of the Advanced Beam Control System

for beam steering, beam control, rapid optical

retargeting, and self-alignment.

Dahlgren engineers concentrated its internal

laser efforts on medium-power soft-kill weapons.

They performed tests against sensors and cameras,

and investigated damage thresholds. In the

late 1980s, Dahlgren engineers worked with optical

augmentation to locate enemy optics for targeting

and on green laser dazzlers for defense against

small-boat attack. There were efforts to harden

electro-optical equipment, including sights and

night-vision systems for the Marines, and laser

eye-protection filters for goggles and binoculars.

Laser systems were also investigated for remotely

cutting holes and wires to disable electronics. Lethality

work continued under funding from the

Joint Technology Office for High-Energy Lasers to

look at alternative wavelengths and pulse shapes in

addition to modern target materials.20



Dahlgren scientists continued to investigate

laser-damage thresholds for materials, components,

and subsystems for a variety of laser

technologies. Near the start of the 21st century,

Figure 10. Early Electromagnetic Launcher at Dahlgren




22

Directed Energy


Past, Present, and Future



commercial lasers based on pumping optical fibers

with semiconductor lasers became common

and more powerful. Dahlgren purchased the Navy’s

largest collection of fiber lasers in 2004 and

began investigating ways to combine multiple

beams into a laser weapon. These lasers have very

high efficiencies, above 20 percent, and the fiberoptic

output reduces the requirement for complex

optical paths. In 2008, Dahlgren engineers demonstrated

a laser capability to ignite spinning mortar

rounds, and in 2009, engineers demonstrated

the capability of fiber lasers in a shoot down of soft

targets at China Lake, California.

Resurgence of Directed Energy

With the fall of the Soviet Union and a greatly

altered threat, DoD funding (particularly technology

funding) experienced an overall decline in the

late 1980s and early 1990s. This caused Navy managers

to emphasize near-term, lower risk, evolutionary

concepts. The Pulsed Power Technology

Program and the Navy’s Charged Particle Beam

Program both came to an end. Investigations into

HPM weapons declined as the difficulty of burnout

of military electronics—articularly analog

components—ecame apparent. Problems with

propagation and cost caused the Navy to greatly

reduce efforts on chemical lasers. With the cancellation

of major programs, Dahlgren used internal

funding in 1990 to keep a core technical capability

together, which was necessary for the Center to

remain in the mainstream of tactical DE and its

associated technologies. Efforts continued in water

breakdown, testing of contractor-developed

pulsed-power components, and electric guns.

New talent and technologies from universities

were brought in to jump-start new projects. Tunable

waveform generators using unique semiconductor

materials were developed. These used bulk

semiconductor material, fabricated in-house, that

could be used as a fast switch controlled by laser

light for both on and off operation. This allowed

faster repetition rates and better triggering than

could be done with small spark gaps, as well as

the ability to create specific waveforms.21 “Green”



technologies were also investigated using nonthermal

plasmas and spark-gap shock waves for

cleaning and pollution reduction.22 New types of



particle detectors and magnetic field sensors were

developed, and new methods of infrastructure

protection were investigated.23 Soft-kill weapons,



both optical and HPM, continued to be studied.

Short-pulse jamming of spread-spectrum systems

was investigated, as well as beat-wave coupling

and special waveforms.24



A number of trends led to a resurgence of

DEWs by the end of the 20th century. The DoD

trend in using digital electronics and off-the-shelf

commercial technologies increased dramatically.

The pace of change in electronics and computers

changed rapidly, too. Most of these new electronic

systems had never been tested for vulnerability, and

there was a question of how much they would increase

military vulnerability to RF or HPM attack.

The reduced emphasis on nuclear EMP shielding

meant more military electronics were not as well

protected from RF attack. Consequently, interest

in protecting U.S. military and civilian infrastructure

increased, including systems in foreign countries.

Moreover, with the increasing reliance on

civilian infrastructure, such as power, communications,

and emergency and industrial systems—all

of which were controlled by digital electronics—

the potential that an adversary could attack infrastructure

systems to affect or divert military

operations became an increasing concern. Following

several major terrorist attacks during this time

period, there was also concern about the impact of

an RF attack on airport towers, financial systems,

alarm systems, and industrial plants. Human factors—

such as a state of confusion experienced by

humans—also played an important part in determining

the overall effects of an RF attack.

The asymmetric threat—where large numbers

of cheap weapons in a swarm attack could overrun

a few sophisticated weapons—caused more concern.

As the asymmetric threat to the surface Navy

pushed the limits of conventional defensive systems,

DE—with it speed-of-light propagation, softkill

potential, and cheap rounds—offered tactical

advantages, either as an adjunct to conventional

systems or as stand-alone systems. Additionally,

there was an increased emphasis on nonlethal, precise

accuracy and graduated effects that could be

used. Moreover, the idea that future battles would

be fought together with civilians and friendly forces

on the battlefield increased the importance of

low collateral damage and antimateriel attacks.

The Joint Program Office for Special Technology

Countermeasures (JPO/STC), located at Dahlgren,

began efforts concerning the vulnerability of

new digital systems to RF attack. The program also

established a DoD-wide database of vulnerability

data, source designs, and RF-effects information—

bringing together much of the information collected

by the services over the years. The program

looked at the protection of modern digital infrastructure

systems and funded a facility constructed

in 1992 to test large-scale electromagnetic vulnerabilities

to various methods of attack.

23


Historical Overview of

Directed-Energy Work at Dahlgren


In the late 1990s and early 2000s, Dahlgren

initiated programs regarding the potential for RF

attack using nonkinetic disruption, with minimal

collateral damage. Capital investment funds

were used to construct a test facility for this effort

in 1998. Dahlgren developed RF payloads

for remotely piloted vehicles and demonstrated

their effectiveness in field tests in 1999, and in

similar tests in 2007. The successful completion

of Project Guillotine was DoD’s first demonstration

of this type of HPM technology. As the need

for statistical vulnerability to commercial digital

systems became apparent, Dahlgren constructed

instrumented test facilities in 1999 and 2002.

Two multistory buildings could be reconfigured

to reflect different types of building construction

and electromagnetic shielding. Large complexes

of electronics, computer networks, server systems,

telephone systems, security systems, and

various types of digital industrial controls could

be assembled, instrumented and exposed to attack

from an external device or technique. This

program-funded complex—alled the Maginot

Open Air Test Site (MOATS) facility—ontinues

to be used to test target systems, as well as a variety

of RF weapon technologies developed internally

and by external and international organizations.

A picture of the MOATS facility is shown in

Figure 11.

As the need for additional DE laboratory space

and testing capabilities became apparent, Dahlgren

applied for military construction funds, and

in 2008, constructed the Naval Directed Energy

Center (NDEC), with access to Dahlgren’s overwater

test range. Other construction funds were

used to construct a remote facility at the Pumpkin

Neck Explosive Test Range to serve as a laser backstop

and measurement facility, as well as an explosive-

test staging area. These facilities already have

been used to develop and test fiber lasers against

modern threat targets. Construction is currently

underway to build an expansion of the NDEC and

a 120-m laser test laboratory building using an existing

tunnel structure. This collection of facilities

represents very important capabilities to develop

and test future DE systems.

Conclusion

For over 40 years, the Naval Surface Warfare

Center, Dahlgren Division (NSWCDD) has been

a leader in developing DE devices, pulsed-power

systems, and electric weapons. Its people have

contributed many publications and patents, and

set world records. DEWs tend to be complex and

technically challenging to build. Regardless, these

weapons offer important, powerful advantages,

such as:

Deep Magazines

Cheap Rounds

Fast Targeting

Variable Lethality

Pinpoint Targeting



As a result of NSWCDD’s leadership, persistent

scientific initiatives, and leading-edge engineering

Figure 11. MOATS Facility Undergoing Testing with an RF Weapon (on right)




24

Directed Energy


Past, Present, and Future



over the years, naval warfighters will increasingly

find themselves turning to DEWs when dealing

with situations spanning the spectrum of conflict.

References

1. Moran, S.L., “High Repetition Rate L-C Oscillator,” IEEE Transactions

on Electron Devices, Vol. ED-26 No. 10, October 1979.



2. Fitch, R.A. and Howell, V.T.S., “Novel Principle of Transient High-

Voltage Generation,” Proceedings IEEE, Vol. III, April 1964.

3. Ramrus, A. and Rose F., “High-Voltage Spiral Generators,” 1st International

Pulsed Power Conference, Lubbock Texas, pIIIC9, November



1976.

4. Landecker, K.; Skatterbol, L.V. and Gowdie, D.R., “Single Spark Ring

Transmitter,” Proc. IEEE, Vol. 59, No. 7, July 1971, pp. 1082–1090.

5. Erickson, D.J.; Fowler, C.M. and Caird, R., EM Radiation from an

Explosive Generator System Coupled to a Large Antenna, Los Alamos



Scientific Laboratory Report M-6-258, March 1978.

6. Fowler C.M. and Brooks, M.L., Explosive Flux Compression Devices

Project, ARPA Order No. 2161, Semiannual Technical Report,



1 March 1972–31 August 1972.

7. Zahn, M.; Ohki, Y.; Fenneman, D.; Gripshover, R. and Gehman,

V., “Dielectric Properties of Water and Water/Glycol Mixtures

for Use in Pulsed Power System Design,” Proceedings of the IEEE,



September 1986, pp. 1182–1221.

8. Gehman, Jr., V.H.; Gripshover, R.J.; Berger, T.L.; Bowen, S.P. and Zia,

R.K.P., “Effects of Filtration on the Impulse Breakdown Strength of

High-Purity Water,” IEEE 1995 Tenth International Pulsed Power

Conference, Albuquerque, New Mexico, 10–13 July 1995.

9. Moran, S.L., Pulsed-Power Technology Program: Accomplishments

in Switching, NAVSWC Tech Note TN-89-259, 1990.



10. Berger, T.L.; Gehman, Jr., V.H.; Lindberg, D.D. and Gripshover,

R.J., “A 2.5 Gigawatt Liquid Dielectric Coaxial Pulse Forming

Line,” Proceedings of the 6th IEEE International Pulsed Power Conference,



Arlington, Virginia, 29–30 June and 1 July 1987.

11. Bernardes, J.S., “A High Power Fast Response Switch Testing System,”

7th IEEE Pulsed Power Conference, June 1989.

12. Moran, S.L. and Hutcherson, R.K., High-PRF High-Current Switch,



U.S. Patent No. 4,912,396, 27 March 1990.

13. Moran, S.L. and Hardesty, L.H., “High-Repetition-Rate Hydrogen

Spark Gap,” IEEE Transactions on Electron Devices, Vol. 38, No.4,



April 1991.

14. Rose, M.F. and Huddleston, C.M., Pulsed Power and Directed Energy

Technology, 10th Anniversary Technical Symposium, NSWC



MP 84-560, October 1984.

15. Moran, S.L., “Hydrogen Spark Gap for High-Repetition-Rate

Compact Accelerators,” NSWCDD Technical Digest, NSWCDD/



MP-92/104, September 1992, pp. 126–139.

16. Bernardes, J.S. and Merryman, S.,“Parameter Analysis of a

Single Stage Induction Mass Driver,” Proceedings of the Fifth

IEEE Pulsed Power Conference, Arlington, Virginia, June 1985,



pp. 552–555.

17. Bernardes, J.S., “Muzzle Velocity Control with Electrothermal

Guns,” Proceedings First Navy Independent Research/Independent

Exploratory Development Symposium, Laurel, Maryland, June



1988, Vol. 2, pp. 123–131.

18. Bernardes, J. S., “Focusing Induction Accelerator,” Proceedings of

the Sixth IEEE Pulsed Power Conference, Arlington, Virginia, June



1987, pp. 735–738.

19. Bernardes, J.S., Sliding Breech-Block for Repetitive Electronic Ignition,



Patent Number: 5,233,902, 10 August 1993.

20. Kim, H.S. et al., “Effects of Chopping Laser Penetration of Metal

Targets,” Applied Physics Letters, 55 (8), 21 August 1989.



21. Stoudt, D.C. and Schoenbach, K.H., “The Electrical Characteristics

of Semi-Insulating GaAs for High-Power Switches,” 7th IEEE

Pulsed Power Conference Proceedings, June 1989.



22. Grothaus, M.G. et. al., “Gaseous Effluent Treatment using a Pulsed

Corona Discharge,” Proceedings of 10th IEEE Pulsed Power Conference,



Albuquerque, New Mexico, July 1995.

23. Gripshover, R.J. et. al., Power Frequency Magnetic Field Detection

Systems, Patent No. 6,483,309, 19 November 2002.

24. Spread Spectrum Countermeasures Final Report, E-Systems, Inc.,



Melpar Division under NSWC contract # N68786-82-C-0109.

25


Historical Overview of

Directed-Energy Work at Dahlgren


NAVSEA Warfare Centers


26


Directed Energy


Past, Present, and Future



History of Laser Weapon Research


By Melissa Olson



The idea of using light as a weapon can be traced back to Hippocrates, commander

of the Greek forces in 212 B.C. His forces supposedly set fire to the sails of the Roman

fleet by focusing sunlight with mirrors. Weapons systems based on lasers and “ray guns,”

long a staple of science fiction, have captured the imagination of people everywhere. But

with steady progress toward the development of lasers in the last 40 years, viable, stateof-

the-art laser weapon systems have now become a reality.

The production of lasers in the modern scientific world is fairly new. The first laser

was developed in the 1960s and represented the beginning of a drastic change in how

the military viewed warfare. The late 1970s and 1980s, too, marked a busy time period

for developing lasers into possible weapon systems. All branches of the military and

industry were striving to master high power levels, beam control, and adaptive optics.

In 1999, the Department of Defense (DoD) formally recognized lasers as future weapons

and began research and development (R&D). In 2000, the Joint Technology Office

for High Energy Lasers was formed to bring all laser technologies together to develop a

complete laser weapon system that could be used by the warfighter.


Electromagnetic Spectrum

The electromagnetic spectrum contains all the types of electromagnetic energy, including

radio waves, microwaves, infrared, visible light, ultraviolet, and gamma rays.


Laser is an acronym for “light amplification by stimulated emission of radiation.” Light,




therefore, is a type of electromagnetic radiation. Light is made up of tiny packets of energy

called photons. The amount of energy is what determines the wavelength. Lasers

are usually infrared (1 mm to 750 nm) and visible light (750- to 400-nm wavelength).

Microwaves are mostly high-frequency radio waves (millimeters to centimeters), with

wavelengths 10,000 times longer than lasers. Diffraction of any electromagnetic radiation

beam is based on the wavelength and aperture size. For the same aperture size, lasers

diffract 10,000 times less than microwaves. This allows the beam to reach farther

ranges while maintaining a small spot size of concentrated energy on the target. Lasers

are preferred in specific scenarios because of minimal diffraction. The electromagnetic

spectrum is shown in Figure 1.


Laser Fundamentals

The quantum mechanical idea of stimulated emission of light was discovered by

Albert Einstein in 1917 and is one of the fundamental ideas behind the laser. Einstein


27


History of Laser Weapon Research


theorized that when a photon interacts with an

atom or molecule in an excited state, two photons

are produced when the atom or molecule leaves the

excited state. Population inversion occurs when the

atoms or molecules are in the excited state. In order

for molecules to come out of the normal “ground”

state, a source of power must be introduced to the

system energizing the atoms to the excited state.

When many photons are passed through many excited

atoms, more and more photons are produced.

The photons are contained and reflected back and

forth in a cavity, with mirrors usually on each end.

The mirror on the output end is only partially reflective,

allowing some photons to leak through,

creating the laser beam.

The difference between an everyday light bulb

and the light of a laser is temporal and spatial coherence.

In a light bulb, the light emits photons

equally in all directions. The light is random, out of

phase, and multiwavelength. A laser emits coherent

light, so photons travel in identical direction

and phase. A laser is also monochromatic, i.e., light

of one wavelength. Another significant difference

is that laser light is highly collimated, which means

the laser beam can travel long distances with minimum

spreading.

The laser gain medium through which the photons

travel to become amplified or magnified can

vary. The source of power used to excite the medium,

achieving population inversion, can be the result

of a chemical reaction, an electric discharge,

a flash lamp, another laser, or some other excitation

mechanism. The type of the lasing medium

determines the type of laser. The three categories

in which lasers are usually classified are chemical,

gas, and solid state. A laser can also be continuous

wave (CW) or pulsed. Each type of laser produces a

specific wavelength of radiation. It is important to

note that different wavelengths of radiation interact

with the atmosphere differently. A laser beam is

either scattered or absorbed by air molecules, water

vapor, or dust. Longer wavelengths scatter less and

are absorbed more than shorter wavelengths; our

sky is blue because the shorter blue wavelengths

of light are scattered more than the longer wavelengths.

1 Gamma rays are so highly absorbed that



they cannot propagate more than a few feet in the

air. Thus, some laser wavelengths are scattered or

absorbed more than others. This makes laser wavelengths

with minimum absorption better for use

as directed-energy weapons since they propagate

through the atmosphere better than others. For example,

the carbon-dioxide (CO2) laser is strongly



absorbed by water vapor, so any use near the ocean

will be negatively affected. Near-infrared and infrared

lasers have shorter wavelengths with negligible

absorbance. The optimal laser choice, therefore,

would be a wavelength-tunable laser that could

vary depending on the atmospheric conditions,

such as the free-electron laser (FEL).

Lasers have affected almost every type of modern

technology. Most laser technologies use low

Figure 1. Electromagnetic Spectrum




28

Directed Energy


Past, Present, and Future



powers and were mastered very quickly. They are

used in many everyday appliances, such as scanning/

inventory devices, surgery/medicine, hair removal,

presentation pointers, law enforcement,

ranging and sighting devices, welding applications,

and much more. Using a laser as a weapon has

many advantages. For example, a laser:

Is unaffected by gravity

Causes minimal collateral damage

Travels at the speed of light

Can precisely reach far distances

Is capable of causing a specific,



predetermined amount of damage to targets

The theory behind these capabilities makes the

laser weapon a prime choice in multiple engagement

scenarios. However, developing lasers with

higher powers to use as a weapon has proven more

difficult than first considered.

Military Laser History

and Laser Types

Generally, a laser weapon is any laser used

against the enemy with more than 50 kW to megawatts

of power. This is much greater power than

commercial lasers. Accordingly, they have greater

support needs, including:

Environmental and personnel safety

Mirror coatings

Chilling requirements

Power requirements

Laser fuel storage

Alignment and tracking requirements



In 1960, the very first laser (a ruby laser) was

built, producing minimal power. This event was

followed by many other laser technology developments.

The first chemical laser, hydrogen fluoride

(HF), was built in 1965, producing 1 kW. It was

then that DoD became interested in researching

and developing a more powerful laser for weapon

applications. Subsequently, in 1968, the Defense

Advanced Research Projects Agency (DARPA)

Baseline Demonstration Laser produced 100 kW,

and the Navy-ARPA Chemical Laser (NACL) produced

250 kW in 1975. The very first laser is depicted

in Figure 2.

Solid-State Lasers (SSLs)



An SSL uses a solid lasing medium, such as a

rod made up of glass or crystal, or a gem, like the

ruby laser. Along with the rod or host material is

an active material, such as chromium, neodymium,

erbium, holmium, or titanium. Chromium is

the active material used in ruby lasers. Neodymium

is the active material in the most widespread

applications. A flash lamp, arc lamp, or another

laser carries out the optical cavity pumping to

achieve population inversion and stimulate the laser

beam. The Neodymium Yttrium-aluminum

garnet (Nd:YAG) laser is a popular SSL. It operates

at a 1064.5-nm wavelength and can be pulsed

wave or CW. A great advantage of these lasers is

that the wavelength and pulse duration can be varied

considerably.1 The power level can reach up to



megawatts when using Q-switching to achieve

Figure 2. First Ruby Laser Developed in 1960 by Research Physicist Theodore H. Maiman



Power

Supply

Switch

Ruby Crystal

Components of the First Ruby Laser


100% Reflective Mirror Quartz Flash Tube



Polished Aluminum

Reflecting Cylinder

95% Reflective Mirror Laser Beam




29


History of Laser Weapon Research


short pulse lengths. The various interactions with

the laser and different crystalline materials can

double the electromagnetic frequency, which will

halve the wavelength, bringing the laser beam into

the visible range, 532 nm (green). The wavelength

can be further divided down three or four times,

making this laser range from the near-infrared to

the ultraviolet wavelength. These lasers are commonly

used for rangefinders and target designators.

Other advantages of these lasers are that they

can be made very small, rugged, cheap, and battery-

powered. Characteristics of SSLs are shown

in Table 1.

Chemical Lasers



A chemical laser uses chemical reaction to create

population inversion in the lasing medium. One

example is the Mid-Infrared Advanced Chemical

Laser (MIRACL) developed in the mid-1980s. The

MIRACL is a continuous-wave, mid-infrared (3.8-

μ) laser. Its operation is similar to a rocket engine in

which a fuel (ethylene, C2H4) is burned with an oxidizer

(nitrogen trifluoride, NF3).2 Free, excited fluorine



atoms are among the combustion products.

Just downstream from the combustor, deuterium

and helium are injected into the exhaust. Deuterium

(U) combines with the excited fluorine to create

excited deuterium fluoride (DF) molecules,

while the helium stabilizes the reaction and controls

the temperature.2 The laser’s resonator mirrors



are wrapped around the excited exhaust gas,

and optical energy is extracted. The cavity is actively

cooled and can be run until the fuel supply is exhausted.

The laser’s megawatt-class output power

can be varied over a wide range by altering the fuel

flow rates and mixture. The laser beam in the resonator

is approximately 21-cm high and 3-cm wide.

Beam-shaping optics are used to produce a 14- ×

14-cm (5.5- × 5.5-inch) square, which is then propagated

through the rest of the beam train. Diagnostics

for evaluating the beam shape, absolute power,

and intensity profile are used on each firing of the

laser. The beam can be directed to a number of different

test areas or to the SEA LITE beam director.2



The DF Chemical Laser (MIRACL) and the Sea Lite

Beam are shown in Figure 3.

The laser and beam director were integrated

in the mid-1980s at the Army’s High Energy Laser

Systems Test Facility (HELSTF) at White Sands

Missile Range, New Mexico. Following integration,

extensive tests were conducted in the areas of:

High-power optical components and beampath



conditioning

Beam-control techniques

High-power propagation

Target damage and vulnerability

Target lethality3



Tests supported by the MIRACL included:

The high-power dynamic with flying drone



(BQM-34)

Conventional defense initiative with flying



drone

High-velocity target test with Vandal



Missile

High-altitude target tests with flying drone

Missile and plume tests using the 1.5‑m



aperture

Radiometrically calibrated images and



spectral radiometry

These successful tests are what made many believe

that MIRACL was the first and only successful

laser weapon system developed by the Navy

prior to the Navy Laser Weapon System (LaWS).3





Gas Lasers



Gas lasers are a type of chemical laser that uses a

pure gas or gas mixture to produce a beam. The typical

gas laser contains a tube with mirrors on each

end. One end transmits the beam out of the cavity.

Most gas lasers use electron-collision pumping,

with electric current passing through the gas. Some

use optical pumping with flash lamps. The helium

30

Directed Energy


Past, Present, and Future



neon (HeNe) laser is a very well-known gas laser. It

produces a bright red, continuous beam of low power.

It is used for many applications such as scanning,

alignment, measurement, and stabilization devices.

University students use them in optical training laboratories.

Many larger lasers contain a HeNe inside

the beam path, as well to verify beam alignment.

HeNe lasers are fairly cheap and very rugged. They

can work continuously for thousands of hours.

CO2 lasers are in the gas family. These lasers



were the earliest, truly high-power lasers and have

been among the most crucial lasers used in R&D

for high-energy laser (HEL) weapons. In industry,

the more powerful CO2 lasers are used for welding,



drilling, and cutting. There are many different

types of CO2 lasers that vary in pumping design.

CO2 lasers work by burning a hydrocarbon fuel



(like kerosene or methane) in oxygen or nitrous

oxide. The hot gas flows through a comb of nozzles,

expands quickly, and achieves population

inversion. The gas then flows through an optical

resonator at supersonic speeds, resulting in stimulated

emission and a laser beam.4

CO2 lasers have been researched for use as



nonlethal weapons. The wavelength produced by a

CO2 laser is also absorbed by glass. For example,



the beam does not penetrate a windshield. Thus,

shooting a CO2 laser at a vehicle’s windshield could



deter a threat by damaging the windshield or by

causing a dazzling effect to reduce the visibility of

the driver, while not reaching the driver at all.

The gas dynamic laser (GDL) is a CO2 laser



based on differences in relaxation velocities

of molecular vibrational states. The laser medium’s

gas has properties such that an energetically

lower vibrational state relaxes faster than a higher

vibrational state; thus, a population inversion is

achieved in a particular time. A GDL is shown in

Figure 4. Characteristics of chemical and gas lasers

are identified in Table 2.

Fiber Lasers



Modern fiber lasers are considered SSLs. They

are powered by electricity, making them highly

mobile and supportable on the battlefield. Fiber lasers

use optical fibers as the gain media. In most

cases, the gain medium is a fiber doped with rare

earth elements—such as erbium (Er3+), neodymium

(Nd3+), ytterbium (Yb3+), thulium (Tm3+),

or praseodymium (Pr3+)—and one or several laser

diodes are used for pumping. Optical fibers have

been used in industry, specifically for telecommunications

to transport information via light. With

developing technology, optical fibers have become

high-energy, powerful laser energy sources. Fiber

lasers have proven to have much benefit over traditional

SSLs. They are rugged and do not require

a clean room to operate or maintain, as most other

laser systems do. They also are extremely efficient;

however, they cannot operate well in all

weather conditions. One example is the IPG CW

fiber lasers, which produce moderate beam quality,

causing damage to materials and components

through thermal heating and burn-through. The

Naval Surface Warfare Center, Dahlgren Division

(NSWCDD) purchased eight commercially available

5.5-kW IPG lasers, where two multimode

(seven fibers) lasers are housed per cabinet. This

type of laser is easy to mount due to the flexible fibers.

The IPG CW Fiber Laser is shown in Figure 5.

Miscellaneous Lasers



There are other types of lasers that do not necessarily

fit into the chemical or solid-state categories.

These include semiconductor lasers, used in:

• Television • Radios

• CD Players • Telecommunications

• Dye Lasers • Medicine

• Spectroscopy • Astronomy

There also are the FELs mentioned previously.

The FEL is a completely different breed of laser.

Figure 3. DF Chemical Laser (MIRACL) and Sea Lite Beam



DF Chemical Laser (MIRACL) Sea Lite Beam

31


History of Laser Weapon Research


Figure 4. A laser engineer inspects a gas dynamic laser after installation



aboard an NKC-135 airborne laser laboratory.

Figure 5. IPG CW Fiber Laser System




32

Directed Energy


Past, Present, and Future



bed and was used to provide the first demonstrated

kill of an operational missile in 1978.

Alpha HF—Built for Strategic Defense Initiative

(SDI) Space-Based Laser (SBL)



Alpha, an HF laser, was the baseline technology

for the SBL readiness demonstration (SBLRD). In

1991, the Alpha laser demonstrated megawatt-class

power levels similar to MIRACL, but in a low-pressure,

space operation environment. Alpha demonstrated

that multimegawatt, space-compatible

lasers can be built and operated.

Tactical High-Energy Laser (THEL)



The THEL is a DF chemical laser developed

by the Army. In 2000 and 2001, THEL shot down

28 Katyusha artillery rockets and 5 artillery shells.

On 4 November 2002, THEL shot down an incoming

artillery shell and a mobile version successfully

completed testing. Subsequently, during a test conducted

on 24 August 2004, the system successfully

shot down multiple mortar rounds. These tests represented

actual mortar threat scenarios in which

both single mortar rounds and salvo were tested

and intercepted. A photograph of THEL is shown

in Figure 6.

Advanced Tactical Laser (ATL)



The ATL uses a closed-cycle, chemical oxygen-

iodine laser (COIL) with beam control, which

lases at a 1.315-μ wavelength. The ATL was developed

to engage tactical targets from a moving platform

at ranges of approximately 10 km. It can spot

a 10-cm-wide beam on a distant target for up to

100 shots. This beam has enough power to slice

through metal at a distance of 9 miles. The aircraft

equipped with the ATL weapon system is shown in

Figure 7.

A specially modified 46th Test Wing NC-130H

aircraft equipped with the ATL weapon system

fired its laser while flying over White Sands Missile

Range, New Mexico, successfully hitting a target

board located on the ground. Equipped with a

chemical laser, a beam control system, sensors, and

weapon-system consoles, the ATL is designed to

damage, disable, or destroy targets with little or no

collateral damage.

Airborne Laser (ABL) (CO2) Chemical Oxygen
The ABL C-130H aircraft contains three laser

beam systems: the powerful killing primary laser

beam (ATL), a set of illuminating laser beams for

infrared surveillance and high-speed target acquisition,

and a beacon laser for a high-precision laser

target tracking beam control system. The primary

It uses electrons to create photons instead of some

type of matter. The electrons are produced, collected,

and directed to flow at very high speeds. To

excite the electrons, they are passed through a “wiggler,”

i.e., a series of magnets positioned in such a

way that electromagnetic radiation (light) is produced

when the electrons release photons. The significant

feature of the FEL is that the wavelength

can be controlled, depending on the magnet positions

and the speed of electrons. This versatility

makes the FEL particularly appealing. However,

the footprint of the FEL system is too large to transform

into any ideal defense weapon. The Jefferson

Laboratory in Newport News, Virginia, has an FEL

and continues to maintain and test its capabilities

and effects. This laser was new to the military in the

late 1990s and received funding to optimize its capabilities

and integrate as a defense weapon. Although

great progress has been made, the required

footprint could be much larger than desired. Consequently,

some interest in the FEL has shifted to

other HEL sources.

Many scientists foresee the probability of using

the laser as a global weapon. This possibility is

proven through basic laws of physics. Actually implementing

such a system, however, can be more

difficult. The global weapon concept uses a base

laser with optics and is strategically positioned in

space to be able to direct its beam multiple places

on Earth at the speed of light with maximum

power levels. This idea faces significant problems,

including appropriate power levels, optics to handle

such levels, propagation issues, and the ethical

measures behind any global weapon. Still, the idea

presents interesting possibilities.

Laser Weapon Development

The following paragraphs highlight some of

the laser weapons that have been successfully developed

over the last 40 years.

Baseline Demonstrator Laser (BDL) Hydrogen

Fluoride (HF)



In 1973, TRW Inc. produced the world’s first

high-energy chemical laser, the Baseline Demonstration

Laser, for DoD. After that, TRW Inc. produced

and demonstrated six more HELs, including

the MIRACL (1985) and Alpha (2000), the nation’s

only megawatt-class chemical lasers.

Navy-ARPA Chemical Laser (NACL) HF



The NACL was mated with the Navy Pointer

Tracker at TRW Inc.’s San Juan Capistrano, California,

facilities in the 1975–978 time frame. This

was the Navy’s initial, integrated HEL system test

33


History of Laser Weapon Research


Figure 6. Tactical High-Energy Laser (THEL)



laser beam is generated by a megawatt COIL located

at the rear of the fuselage. The high-power laser

beam travels towards the front of the aircraft

through a pipe. The pipe passes through a Station

1000 bulkhead/airlock, which separates the rear

fuselage from the forward cabins. The high-power

beam passes through the fine beam control system

mounted on a vibration-isolated optical bench.

Beam pointing is achieved with very fast, lightweight

steering mirrors, which are tilted to follow

the target missile. The ABL finally destroyed a target

while in flight at White Sands Missile Range in

August 2009. The 12,000-lb ABL locked onto an unspecified

ground target and fired the laser, making

the target disappear. Although it was successful at

this demonstration, using the ABL in the fleet has

fallen out of favor due to affordability and technology

problems. The ABL is shown on an aircraft in

Figure 8.

Joint High-Power Solid-State Laser (JHPSSL)



In hopes of accelerating SSL technology for

military uses, work is being performed by the

U.S. Army Space and Missile Defense Command

(SMDC) and the Army Test and Engineering Center

at White Sands Missile Range. The technology

uses an electric laser diode to shoot light into 32

garnet crystal modules that combine to create “laser

amplifier chains” producing 15 kW. By using seven

chains and by combining multiple beams, they

have reached 105 kW in the laboratory operating

in a clean room. The program’s ultimate goal is for

a laser system to reach high powers outside a laboratory

environment. Fielding such a delicate optical

structure can present significant barriers for this

laser system. Nonetheless, it will be a great accomplishment

for a variety of force protection missions,

such as shipboard defense against cruise missiles.

The JHPSSL system is shown in Figure 9.

Navy Laser Weapon System (LaWS)



The Navy LaWS is the most recent, successful

laser weapon. It uses an electric-fiber laser design,

avoiding the problems that chemical lasers

present. In the summer of 2009, the Naval Sea

Systems Command (NAVSEA)—with support

from NSWCDD—successfully tracked, engaged,

and destroyed unmanned aerial vehicles (UAV)

Figure 7. 46th Test Wing NC-130H Aircraft Equipped with the



ATL Weapon System

34

Directed Energy


Past, Present, and Future



Figure 8. Airborne Laser (ABL)

Figure 9. Joint High-Power Solid-State Laser (JHPSSL) System




35


History of Laser Weapon Research


in flight at the Naval Air Warfare Center, China

Lake, California. A total of five targets were engaged

and destroyed during the testing, which

represented a first for the U.S. Navy. The laser was

fired through a beam director on a Kineto Tracking

Mount similar to the Sea Lite beam director.

The system used fiber lasers in the configuration

and has proven to be a rugged and dependable

choice for the warfighter’s needs. A photograph of

LaWS is shown in Figure 10.

Laser weapon systems development in recent

years has taken giant steps forward. Dedicated

R&D has advanced the state of the art considerably.

What was unimaginable only a few short

years ago, today has become reality. Accordingly,

given continued R&D, warfighters in the near

term will have additional weapon options to

choose from for dealing with a spectrum of threats

and contingencies.

References

1. Beason, Doug Ph.D., The E-Bomb: How America’s New Directed

Energy Weapons Will Change The Way Future Wars Will Be Fought,



Da Capo Press, 2005.

2. Pike John, Mid-Infrared Advanced Chemical Laser (MIRACL), FAS

Space Policy Project, Military Space Programs, March 1998, http://




www.fas.org/spp/military/program/asat/miracl.htm


3. Albertine, John R., “History of Navy HEL Technology Development

and Systems Testing,” (Proceedings Paper), Proc. SPIE,



Vol. 4632, Laser and Beam Control Technologies, Santanu Basu

and James F. Riker, Eds., pp. 32–37.

4. Anderberg, Major General Bengt and Dr. Myron L. Wolbarsht, Laser

Weapons: The Dawn of a New Military Age, Plenum Press, New



York, 1992.

Figure 10. Navy Laser Weapon System (LaWS)





36


Directed Energy


Past, Present, and Future



Laser Weapon System (LaWS) Adjunct to the

Close-In Weapon System (CIWS)


By Robin Staton and Robert Pawlak


37


Laser Weapon System (LaWS) Adjunct to the

Close-In Weapon System (CIWS)


The Naval Sea Systems Command (NAVSEA)

established the Navy Directed Energy Weapons

Program Office in January 2002 and subsequently

chartered the Directed Energy and Electric Weapon

Systems Program Office (PMS 405) in July

2004.1, 2 Its mission is to change the way the Navy



fights in the 21st century by transitioning directedenergy

and electric weapon technology, providing

the warfighter with additional tools to fight today’s

and tomorrow’s wars. In support of this mission,

the Laser Weapon System (LaWS) was developed,

which potentially adds a suite of tools for offensive

and defensive operations.

The LaWS program is managed by PMS 405 in

cooperation with the Program Executive Office Integrated

Warfare Systems (PEO IWS), the Navy’s

Close-In Weapon System (CIWS) manager. A multilaboratory/

multicontractor organization led by

the Naval Surface Warfare Center, Dahlgren Division

(NSWCDD), has been executing the program

since March 2007. The potential advantages of a lethal,

precise, speed-of-light weapon are numerous

and have been recognized for many years. However,

even in light of these advantages, there are realities

that need to be considered for any program to

succeed to the point that an actual system is placed

in the hands of the warfighters.

The LaWS system offers viable solutions for an

important subset of threats while fitting into acceptable

size and weight constraints. In addition,

since LaWS is a fully electric laser, the operation

of the system does not require the handling and

storage of hazardous chemicals, such as hydrogen

fluoride. As will be discussed later, due to the incorporation

of high levels of commercial off-theshelf

(COTS) technology, the LaWS system also

has advantages for topside design, logistic supportability,

and cost. Thus, LaWS could enable the

Navy to address adverse cost-exchange situations,

which can occur when engaging proliferated inexpensive

threats such as unmanned aerial vehicles

(UAVs).

Background

Based on mission analysis work conducted prior

to the LaWS program and additional work done

as part of the program, it became clear that a number

of factors require careful consideration. First, a

high-power laser is not likely to replace anything

on a ship in the next 5 years. For a new system to

be added to a ship, a high-power laser must supplement

current capabilities or provide new capabilities

that clearly justify its addition. Second, because

a laser provides such a diverse set of capabilities,

conventional air-to-air warfare (AAW) models—

such as the Fleet AAW Model for Comparison of

Tactical Systems (FACTS), Antiair Warfare Simulation

(AAWSIM), and Extended Air Defense Simulation

(EADSIM), as well as other existing AAW

analysis approaches—are not well suited for showcasing

current or near-term laser-weapon capabilities.

While they can (and have) been used for

laser-weapon analysis, their application to a megawatt-

class laser that could “instantly” destroy boats

or cruise missiles (akin to missile engagements) is

a more straightforward application of the existing

models and techniques.

In November 1995, the Chief of Naval Operations

requested that the National Research Council

initiate, through its Naval Studies Board, a

thorough examination of the impact of advancing

technology on the form and capability of the naval

forces to the year 2035. A major observation of the

report is quoted below:

Numerous laboratory and field-test versions

of laser weapons have been developed

and demonstrated. They have worked as

expected and demonstrated suitable lethality

against their intended targets. The primary

factors that have inhibited the transition of

the technology into deployed systems are size

and weight. Generally, the conceptual designs

of laser weapons that are scaled for combat

effectiveness are too large to be appealing to

users; conversely, weapons that are sized for

platform convenience generally lack convincing

lethality.3



Subsequently, an August 2006 U.S. Air Force

(USAF) Scientific Advisory Board Study examined

the increasing threat posed by UAVs in some detail.

Key conclusions included:

No single system can completely address

the UAV threat. A single sensor solution

is inadequate because of the size and speed

challenges presented by small UAVs. A single-

weapon-layer solution fails to provide for

adaptability to multiple scenarios or adequate

probability of kill.

Key recommendations of the USAF Advisory

Scientific Board Study included:

Develop and field longer-term upgrades

to counter increased UAV threats. They

include:…a small, multimission air/air and

air/ground weapon; and directed-energy air

defense weaponry.4




38

Directed Energy


Past, Present, and Future



In addition to the USAF Scientific Advisory

Board study, a 2007 OPNAV Deep Blue Study

noted the potential advantage of nonkinetic defeat

options and recommended that the Navy accelerate

development of nonkinetic systems to include

high-energy lasers (HELs).5



The laser power levels likely to be available in

the near term, within reasonable size and cost, are

in the neighborhood of 100 kW of radiated power.

While this power level is not adequate to engage

certain threats, such as cruise missiles or

tactical ballistic missiles at tactically useful ranges,

there is still a wide spectrum of threats that could

be engaged at ranges that are comparable to many

current ship-defense weapons, including minorcaliber

guns and small missiles. The spectrum of

threats includes:

UAVs

Missile Seekers

Intelligence, Surveillance, and



Reconnaissance Systems

Rockets

Man-Portable Air-Defense Systems



(MANPADS)

Mortar Rounds

Floating Mines

Artillery Rounds



LaWS on CIWS

The Mk 15 Phalanx CIWS can often detect,

track, and (sometimes) identify potential

threats at ranges well outside the effective

range of the 20mm gun. These functions are

accomplished using the search/track radar system

and the Phalanx Thermal Imager (PTI).

When added to the Phalanx mount and pointed

in the same direction as the gun (see Figure

1), a laser weapon could potentially add

a number of useful functions and capabilities

to the mount, but technical challenges must

be overcome. Preliminary analyses of the mechanical

characteristics of the mount suggest

that the additional weight that could be added

to the mount must be kept under approximately

1200–1500 lb. Additionally, it is highly

desirable that the addition of the laser weapon

not substantially affect the train/elevation

operation of the mount in angle, peak velocity,

or acceleration. Consequently, use of rapidly

evolving fiber laser technology appears to be

the only currently foreseeable path to adding

significant laser energy directly to the mount

within these constraints.

One major driver in the genesis of the

LaWS system was the availability of relatively

low-cost COTS fiber-optic lasers. Because these fibers

are flexible, they obviate the need for an expensive

coude path system (an optical mirror/lens

assembly that turns radiation 90° and may also support

rotation of the beam director), thus allowing

the use of low-cost mount technology, as well as the

retrofitting of the system on existing mounts. The

last factor is extremely important because of the

scarcity of topside real estate on today’s ships. These

fiber-optic lasers do have limitations in terms of

power, although power levels are growing with advancing

technology. The reality today is that, in order

to get adequate lethality from a system based on

this technology, the use of a beam-combining apparatus

utilizing several individual fibers is necessary.

(Figure 2 depicts combining multiple fibers in

the same beam director.) Furthermore, a smaller

beam size is desirable since this drives power density

up—ncreasing the performance required for the

tracking and pointing elements of the system. Thus,

a high-resolution fine track sensor is needed, as well

as an appropriately robust line-of-sight control.

A Potential Suite of Laws-

Related Capabilities

Potential added capabilities that an adjunct

LaWS could contribute to the total ship combat

system are briefly outlined in the following subsections.

Figure 1. LaWS Mounted on CIWS




39


Laser Weapon System (LaWS) Adjunct to the

Close-In Weapon System (CIWS)


Target Identification, Tracking, and Intent

Determination at Range



The optics that would be added for the laser

to detect and track targets in support of a laser engagement

would immediately contribute additional

capabilities to the entire ship combat system even

without operating the laser. A laser-gated illuminator,

part of the tracking system, significantly increases

the signal to the background level of tracked

targets and provides good range resolution as well.

The additional sensitivity and angle resolution provided

by the LaWS optics would allow the identification,

precision tracking, and “monitoring” (at

high resolution) of potential threats or vehicles of

interest at substantially greater ranges than could

be achieved by the PTI alone. The Phalanx radar,

or another source, would have to provide an initial,

accurate cue to facilitate initial acquisition. Once acquired,

the target could be examined and monitored

with high resolution at range. This capability could

make a substantial contribution to identification efforts—efforts to determine intent and potentially

even to documenting target behavior to resolve issues

with rules-of-engagement doctrine. It is widely

recognized that rules-of-engagement issues, such

as threat identification and intent determination,

are among the most difficult problems faced by ship

commanding officers.

Unambiguous Warning at Range



If a fraction of the laser energy is routed through

a frequency-doubling crystal, an intense, visible

beam can be projected to significant ranges to provide

a clear, unambiguous warning that a potential

target is about to be engaged unless an immediate

change in behavior is observed. This feature also

would have utility for dazzling aircraft, surface vehicle,

or submarine sensors, and would provide exceptional

long-range, unambiguous warning to

boats or aircraft at night.

Figure 2. Cutaway View of the LaWS Beam Director




40

Directed Energy


Past, Present, and Future


Sensor Destruction at Range



Many electro-optical (EO) sensors are quite

susceptible to damage by laser energy in the fiberlaser

band as is the case with infrared (IR) missile

seekers with germanium optics. The frequencydoubling

feature described in the previous paragraph

also would be useful to ensure that a band-pass

filter at a single frequency could not be applied as

an effective countermeasure. The intent here would

be to destroy the seeker or imager at ranges well beyond

those achievable by the Phalanx 20mm gun.

Other examples include intelligence, surveillance,

reconnaissance, and targeting sensors on UAVs or

unmanned surface vehicles (USVs).

IR Missile Assist at Range



Many targets of interest—including UAVs,

USVs, and small boats—are somewhat “marginal”

from a target-signature standpoint, particularly at

the maximum range of existing IR guided missiles

such as the FIM-92 Stinger, the FGM-148 Javelin,

the RIM-116 RAM, and the AIM-9X Sidewinder.

The CIWS laser adjunct could potentially “correct”

this situation by laser heating target vehicles to enhance

their signature to existing IR guided missiles.

Note that this is NOT “conventional” semiactive-laser

(SAL) guidance—he LaWS is not a coded illuminator,

nor do the seekers in question rely on

this coding. The IR missiles would be unmodified

weapons taken from inventory. The LaWS adjunct

would simply contribute laser energy that heats

the target and enhances its signature for the missile.

While, at the ranges envisioned, this laser heating

alone would not be sufficient to “kill” the target,

it could definitely heat the target. It should also be

noted that the laser “illumination” could potentially

be used to preferentially select a specific target

from among a group of targets for engagement by a

missile. It is expected that these engagements could

occur at ranges of two to four times the effective

Phalanx gun engagement ranges. Use of LaWS in

this manner would be exactly analogous to the use

of a SAL designator for a SAL guided missile, such

as the AGM-114 Hellfire. It is expected that similar

rules of engagement would apply.

Direct Target Destruction by Laser Heating



Some threats are known to be vulnerable to direct

destruction by the application of laser energy

for an appropriate period of time. The currently

envisioned system would be able to destroy a subset

of naval threats at ranges comparable to, and

in some cases greater than, the ranges achieved

with modern, stabilized guns using EO fire control

systems and modern ammunition. In the case

of a LaWS adjunct, the addition of the laser would

open new options for a firing/engagement doctrine

and would be expected to conserve CIWS rounds

for use on threats that are not appropriate for this

laser power level. While the laser is often quoted as

having an “unlimited magazine,” the true number

of threats that can be engaged by the laser in any

period of time is limited by the required illumination

time and by the time required to evaluate a

kill and transition to the next target. Thus, for particular

target velocities and numbers, the “effective

laser magazine” might be added to the CIWS magazine

to increase the total number of targets engaged

by the combined system.

LaWS Accomplishments

A government/industry team, led by government

technical personnel, have achieved significant

accomplishments since the start of the LaWS

program in 2007; specifically, the team:

Conducted mission analyses

Developed threat lethality estimates

Performed industry surveys for critical components



and subsystems

Performed extensive trade-off analyses

Designed a prototype system

Constructed the system—the prototype director



and mount (see Figure 3)

Performed numerous laboratory-based tests



of subsystems and the complete prototype

Validated system operation with a full-up



field test at high power using BQM-147A

UAV target drones

Additionally, the team was able to minimize the

cost of the prototype by leveraging hardware that

had already been developed or procured for other

applications, including an L3-Brashear tracking

mount, a 50-cm telescope, and high-performance

IR sensors. Some components were commercially

procured, such as the 5.4-kW fiber lasers. Figure 4

shows three laser cabinets, containing two lasers

apiece, resulting in a total power output of 32.4 kW.

Other components, such as the beam combiner

and much of the system software required for operation

and target tracking, had to be specifically

designed, fabricated, and tested.

The LaWS program achieved a highly successful

field test/demonstration in June 2009 when the

prototype successfully engaged and destroyed five

drone targets at tactically significant ranges at the

China Lake, California, test range (see Figure 5).

Additional Work to be Done

Since the LaWS prototype sits on a dedicated

gimbal, much additional work needs to be done

41


Laser Weapon System (LaWS) Adjunct to the

Close-In Weapon System (CIWS)


Figure 3. Photo of LaWS During Testing at the Naval Weapons Center, China Lake

Figure 4. IPG Laser Cabinets




42

Directed Energy


Past, Present, and Future



Figure 5. BQM-147A During LaWS Engagement



to place the weapon on the CIWS mount. The

latter would require new control systems and

optomechanical hardware for line-of-sight stabilization.

Other aspects of the shipboard environment

are also more stressful, and future mission

areas may require an increasingly robust capability

to deal with optical turbulence and the

high-clutter environment of the ocean surface.

Additional laser power might also be required.

These modifications, depending on the level

of capability desired, will require engineering

modifications to the system. Engineering analysis

and design to address these issues is currently

underway at NSWCDD.

While the aforementioned engineering issues

are important to address, there are additional technical

issues that have yet to be analyzed. These issues

are concerned with the potential utility of

the system. Indeed, most of the detailed technical

analyses and experiments performed thus far

have focused on target destruction, with some effort

expended on the issue of seeker damage/destruction.

Developing credible lethality estimates

for various potential threat targets is clearly very

important, but one consequence of the lethality focus

is that necessary, detailed, defendable technical

analysis, analytic model development, and experiments

have not been performed to explore the other

functions/features that a CIWS Adjunct LaWS

might provide to the overall ship combat system.

Some of these contributions might become “routine”

if the LaWS were available.

For example, a hard-kill engagement of a target

by a Navy shipboard weapon is a relatively rare

event, even during wartime conditions. On the other

hand, ships in combat zones—nd elsewhere—constantly have the problem of detecting potential

threats, tracking them, identifying them, determining

their intent, and providing warning. Thus,

use of the LaWS system, at less than its full lethal

potential, could become a daily, standard practice.

It is still not clear how these potential benefits and

capabilities could be measured or quantified to the

satisfaction of key decision makers.

Likewise, other potential advantages of laser

weapons—uch as the potential for precision engagement,

covert engagement, fire starting, graduated

lethality, low cost per shot, and “unlimited”

43


Laser Weapon System (LaWS) Adjunct to the

Close-In Weapon System (CIWS)


magazine—have not been subjected to rigorous

technical analysis for feasibility, utility, and practicality.

These investigations need to be performed

and are gradually being addressed within the

LaWS program.

Although the Phalanx CIWS system is currently

installed on a number of Navy surface

warships—either a single mount or a double

mount—there are still significant numbers of

ships that do not have a Phalanx system. It is highly

desirable to make LaWS potentially available to

virtually any ship that could benefit from the enhanced

capabilities.

While the technical issues associated with the

addition of LaWS to the Phalanx CIWS will be

somewhat different from those associated with

adding a LaWS system to other weapon systems—

or the provision of a “stand-alone” LaWS—hey do

not appear to be insurmountable. For example, a

LaWS beam director might be added to the stabilized

Mk 38 Mod 2 25mm gun or the Mk 46 Mod 2

30mm gun. A LaWS beam director might be added

to (or even substituted for) the Mk 46 EO Sight

on DDGs or added to the trainable RAM launcher.

Other options may exist as well.

The issue of defending combat logistics force

ships, joint sealift ships, and certain support vessels

from attacks from small boats or UAVs is also relevant.

These ships often have little or no installed defensive

capabilities for potential terrorist or pirate

threats, and expeditionary security detachments do

not have decisive warning or engagement capability.

In addition, there are severe limitations placed

on concept of operations (CONOPS) and rules of

engagement due to the limited objectives/limited

means of the various missions.

A system such as LaWS could provide graduated

lethality from warning to destruction. It also

could provide additional applications to minimize

risk to sea base platforms and enhance sea shield

capabilities against nonstate threats. If acceptable

rules of engagement can be established, the advantages

of graduated lethality might be extended to

ships in port or entering/exiting harbors.

While considerable additional work needs to

be done to produce a tactical system, the LaWS

program’s recent demonstration of capability provides

strong evidence that a useful, tactical system

could be produced within reasonable cost, volume,

weight, and power constraints to provide the warfighter

with a suite of additional tools to fight today’s

and tomorrow’s wars.

References

1. NAVSEA Notice 5400, Ser 09B/240, “Establishment of the Navy Directed

Energy Weapons Program Office (PMS 405),” 4 January 2002.

2. NAVSEA Instruction 5400.101, Ser SEA 06/058, “Directed Energy

and Electric Weapon Systems Program Office (PMS 405) Charter,”

21 July 2004.

3. Technology for the United States Navy and Marine Corps 2000–

2035: Becoming a 21st-Century Force, Naval Studies Board, National



Research Council, National Academy Press, 1997, Volume

5: Weapons, Chapter 6, “Navy and Marine Corps Applications for

Laser Weapons.”

4. Report on the Air Defense Against Unmanned Vehicles, USAF Scientific



Advisory Board, SAB-TR-06-01, August 2006.

5. “Counter Unmanned Aerial Systems (UAS),” OPNAV Deep Blue

Report 08-01, August 2007.




44

Directed Energy


RDT&E, Acquisition, and

Warfare Management



The Acquisition Challenge Associated

With Directed-Energy RDT&E


By Mike Kotzian



An already tense situation quickly escalated. Everyone within the combat information

center of the Navy’s newest all-electric ship suddenly realized that two surfaceskimming,

antiship missiles were bearing down on their destroyer. With less than 30 seconds

to impact, the tactical warfare officer gave the order to fire. Seconds later, the first

surface-skimming missile vanished from all tracking consoles. Another order to fire

closely followed, and the second missile threat was also destroyed. Consequently, within

a matter of 10 seconds from threat recognition to threat elimination, the Navy’s newest

all-electric ship was able to destroy two incoming threats by using one of the Navy’s

newest weapon systems—he free-electron laser.

Does this scenario of a Navy all-electric ship, employing a high-energy laser to

shoot down enemy surface-skimming antiship missiles, sound like inevitable reality or

unattainable science fiction? For scientists and engineers working on directed-energy

systems for the Navy, the answer does not lie solely in the advanced technical challenges

associated with developing directed-energy weapons. Rather, the answer also lies in

how well scientists and engineers understand and adhere to the Department of Defense’s

(DoD’s) Defense Acquisition Management System (DAMS) framework governing the

development of new weapon systems.


Evolution of Defense Acquisition

The way in which DoD identifies needs and subsequently develops, tests, procures,

and sustains weapon systems has evolved over time. Today’s acquisition foundation can

be traced back to the Packard Commission report in 1986, where many of this report’s

recommendations became part of the Goldwater-Nichols DoD Reorganization Act of

1986. This evolution continued along three tracks:

1. Requirements moving from threat-based to capability-based

2. The resource allocation system adding execution reviews with concurrent program

and budget reviews


45


The Acquisition Challenge Associated

With Directed-Energy RDT&E


3. The acquisition process attempting to incorporate

a more flexible and tailored process

These three tracks form the Defense Support

System organizational structure: the Joint Capabilities

Integration and Development System (JCIDS)

process; the Planning, Programming, Budgeting,

and Execution (PPBE) process; and the DAMS

process, respectively. These three processes operate

as “systems of systems” and are referred to as


the “Big A” acquisition process shown in Figure 1.1




While all three of these phases hold their own

level of importance, the major focus for scientists

and engineers at research and development (R&D)

facilities is the “Little a” acquisition process. It is

this “Little a” acquisition process, where the rules

and processes are found, that governs how DoD

goes about developing a new materiel solution to

a validated warfighter requirement. These rules

and processes are codified within DoD Instruction


5000.02, Operation of the Defense Acquisition System,




which was issued in December 2008.

The acquisition framework associated with

DoD Instruction 5000.02 is the DAMS structure.

This framework, shown in Figure 2, consists of numerous

strategically placed milestones and major

program reviews to ensure proper programmatic


oversight.2 Each of the milestones has specific Figure 1. Defense Support System Organizational Structure




with


46

Directed Energy


RDT&E, Acquisition, and

Warfare Management



criteria that must be satisfied before a program is

allowed to further proceed along the DAMS. The

program’s Milestone Decision Authority (MDA)

rests with the individual responsible for deciding

if the milestone criteria have been met and,

if so, for allowing the program to proceed to the

next phase of the acquisition process. Designation

of a program’s MDA depends on a program’s level

of research, development, test, and evaluation

(RDT&E) and procurement funding. For example,

an Acquisition Category (ACAT) I program is defined

as an eventual total expenditure for RDT&E

of more than $365 million in fiscal year (FY) 2000

constant dollars or, for procurement, of more than

$2.19 billion in FY 2000 constant dollars. In this

case, for an ACAT ID (“D” refers to the Defense

Acquisition Board (DAB)) the Under Secretary of

Defense for Acquisition, Technology and Logistics

(USD(AT&L)) is the MDA; for an ACAT IC (“C”

refers to Component or Service), the MDA is the

Head of the DoD Component or, if delegated, the

Component Acquisition Executive.3



In addition, civilian and military workforce

members within the DoD whose job responsibilities

are deemed acquisition-related find themselves

with a training requirement necessary to carry out

their acquisition-related job responsibilities. Specifically,

these workforce members are required to

gain acquisition training and education with the

passage of the Defense Acquisition Workforce Improvement

Act (DAWIA) signed into law in 1990.

The current certification process comprises three

levels covering 16 different career fields. Each of

these 16 career fields has a set of specific training,

education, and experience requirements that

must be met in order for an individual to achieve

Level 1, Level 2, or Level 3 certification. The Defense

Acquisition University (DAU) provides the

necessary training classes required for the certification.

DAU identifies “core-plus” training classes

and continuous learning modules for each level

of certification. The core-plus classes and modules

are not required for certification but are identified

as additional sources of information to assist individuals

in becoming more knowledgeable about

their career field beyond the minimum standards

required for certification. The most up-to-date certification

frameworks for all 16 career fields can be

found at the following DAU website: http://icatalog.




dau.mil/onlinecatalog/CareerLvl.aspx


Defense Acquisition Reform

The DoD acquisition environment is undergoing

continuous change. The issuance of DoD Instruction

5000.02 marked the opening salvo of what

has become seemingly constant updates, modifications,

and guidance impacting how DoD procures

weapon systems to meet warfighter

requirements.

In addition to DoD’s issuance of DoD Instruction

5000.02, the Government Accountability Office

published a stream of reports and findings that indicate

significant cost growth and schedule delays

in major defense acquisition programs. In 2009,

Secretary of Defense Robert M. Gates proclaimed

Figure 2. DoD Acquisition Framework




47


The Acquisition Challenge Associated

With Directed-Energy RDT&E


a new way of doing business within DoD when it

comes to weapon systems acquisition. Pressures are

building for every program to maintain cost and

schedule estimates while delivering the technical

requirements originally developed to support the

warfighter.

Moreover, there have been two major policy

issuances. As previously mentioned, the first was

DoD Instruction 5000.02 in December 2008. This

update of the rules and processes governing DoD

weapon systems acquisition primarily impacted

the early part of the DAMS framework. The problem

was that weapon system programs were failing

their initial operational test and evaluation phases

at alarming rates—many times traced to program

offices attempting to design weapon systems with

immature technology. Such failures were preventing

those programs from proceeding to a full-rate

production decision review and, more importantly,

causing a repeat of some of the DAMS framework,

which translated to increased costs and delayed

initial operational capability timelines.

DoD Instruction 5000.02 attempted to solve

this problem with three main emphases. First, a

mandatory requirement was inserted for competitive

prototyping prior to program initiation at

Milestone B. The intent was to ensure a competition

among contractors competing for a contract award.

The theory was that such a competition would reduce

technical risk, validate designs, improve cost

estimates, evaluate manufacturing processes, and

refine requirements. Reducing technical risks was

especially important because weapon system programs

were expected to demonstrate a technology

readiness level (TRL) of six—where the system/

subsystem model or prototype is demonstrated

in a relevant environment—by the time a program

reached Milestone B. TRLs are categorized

on a scale of 1 to 9. A TRL of 1 is the lowest level of

technology readiness, where scientific research begins

to be translated into applied R&D. A TRL of 9

is the highest level of technology readiness, where

the actual system is proven through successful mission

operations. A TRL of 6 represents a major step

up in a technology’s demonstrated readiness. Using

TRLs enables consistent comparisons of technical

maturity across different types of technologies, giving

program decision makers a common benchmark

to consider when assessing program risk.

Note that TRLs are meant to capture a level of technical

maturity, not the probability of occurrence

(i.e., the likelihood of attaining a required maturity

level) or the impact of not achieving a level of technical

maturity.4



The second emphasis was on a stricter adherence

to systems engineering processes and technical

reviews. Too often weapon system programs

were not closely following systems engineering

processes or avoiding due diligence when it came

to the definition of successful exit criteria for a

technical review. Consequently, all technical efforts

must be outlined in a program’s systems engineering

plan. The program manager will use the

eight technical management processes—ecision

with

48

Directed Energy


RDT&E, Acquisition, and

Warfare Management



analysis, technical planning, technical assessment,

requirements management, risk management, configuration

management, technical data management,

and interface management—to manage the

technical development of the system increments,

including the supporting or enabling systems.5



The program manager will use the eight technical

processes—stakeholders requirements definition,

requirements analysis, architectural design,

implementation, integration, verification, validation,

and transition—to design the system, subsystems,

and components, including the supporting

or enabling systems required to produce, support,

operate, or dispose of a system.6 Figure 3 provides



an overlay of the new DoD Instruction 5000.02

and Secretary of the Navy (SECNAV Instruction)

5000.2D (Implementation and Operation of the

Defense Acquisition System and the JCIDS), and

shows the timing of specific systems engineering

technical reviews as a program matures through

the DAMS.

The third emphasis was a more prominent role

of the MDA, starting with a mandatory requirement

that all weapon system programs seeking a full or

partial materiel solution must hold a Materiel Development

Decision chaired by the MDA. Thus, the

old Design Readiness Review was replaced with the

Post-Critical Design Review Assessment chaired by

the MDA. In short, the MDA was to become a more

prominent figure in the oversight of a weapon system

program’s progress.

The second relatively recent major policy issuance

was the Weapon Systems Acquisition Reform

Act (WSARA) of 2009, implemented by

Directive-Type Memorandum (DTM) 09-027 in

December 2009. This DTM amended DoD Instruction

5000.02, the Defense Federal Acquisition

Regulation Supplement (DFARS), and associated

business practices within the Defense Acquisition

Guidebook (DAG). The WSARA implementation



brought about changes to policies and procedures

across 13 categories. Some of the WSARA changes

most relevant to the Navy directed-energy community

include:

Analysis of alternatives study guidance

Acquisition strategies to ensure competition

Competitive prototyping

Developmental test and evaluation

Systems engineering

Preliminary design reviews

Critical cost growth



The Acquisition Impact

So why should the directed-energy community

care about these acquisition policy changes? Because

these policy changes impact the community’s

Figure 3. Systems Engineering Technical Review Timing




49


The Acquisition Challenge Associated

With Directed-Energy RDT&E


ability to develop, produce, and/or sustain directed-

energy weapon systems. The ultimate goal of

the directed-energy community is to deploy directed-

energy weapons to the fleet. Accordingly, regardless

of which phase or phases an organization

in the community supports, its actions are impacted

by the language in DoD Instruction 5000.02 and

the WSARA of 2009. The more scientists and engineers

in the organization are aware of governing

policy documents like DoD Instruction 5000.02,

the better their chances are of meeting DoD leadership’s

expectations in terms of cost, schedule, and

technical effectiveness.

Actions have shown that DoD senior leadership

has come to expect all weapon system programs

to adhere to the current acquisition-related

policy and guidance changes. As mentioned earlier,

major weapon system programs have recently been

canceled or restructured for not meeting DoD senior

leadership expectations—omething that

rarely occurred previously. In today’s environment,

technology alone will not carry the argument for a

program’s survivability. Directed-energy weapons

definitely carry the allure of a “Star Wars-like” capability,

but these same weapon systems will need

to show sustainable cost and schedule compliance

if they are to come to fruition. Resources are too

limited, and the warfighter has too many needs to

allow unsustainable weapon system programs to

continue. Therefore, everyone involved with the

development, procurement, and/or sustainment of

a directed-energy weapon system needs to have an

adequate understanding of the acquisition underpinnings

now governing DoD.

Summary

The proverbial “winds of change” are blowing

across the DoD acquisition landscape. The

management of major weapon systems dependent

upon cutting-edge technologies—uch as those of

directed energy—annot afford to conduct business

in a manner reminiscent of bygone days.

Everyone involved with the development, production,

or sustainment of a directed-energy weapon

system needs to understand the “rules of engagement”

laid down by the most recent DoD acquisition

policy guidance. Highly skilled scientists and

engineers typically already understand the need

for a structured systems engineering approach to

problem solving. Today, though, more than ever,

cost and schedule must be factored in as potential

tradespace to deliver the ultimate goal: a cost-effective,

directed-energy weapon system delivered in a

timely manner while meeting the warfighter’s requirements.

Scientists and engineers who adhere

to these recent acquisition changes will help their

organizations achieve this goal, thereby ensuring

that warfighters will be armed with the most technologically

superior weapons possible.

References

1. Congressional Research Service Report 7-5700, 10 July 2009, p. 3.

2. Ibid., p. 8.

3. DoD Instruction 5000.02, 8 December 2008, p. 33.

4. Defense Acquisition Guidebook, 5 May 2010, paragraph 10.5.2.2.



5. Ibid., paragraph 4.2.3.1.

6. Ibid., paragraph 4.2.3.2.

50


Directed Energy


Technology, Modeling, and Assessment



The Basics of Electric Weapons and

Pulsed-Power Technologies


By Stuart Moran



What Are Electric Weapons?

Most conventional weapons rely on chemical energy (explosives) as their destruction

mechanism, either to explode on target, like bombs, or to create kinetic energy, like

a bullet. Electric weapons are different. Electric weapons use stored electrical energy,

rather than explosives, to attack or destroy the target. Electric weapons generally fall into

two categories: directed-energy weapons (DEWs) and electromagnetic (EM) launchers.

DEWs send energy, instead of matter, toward a target, and can be separated into three

types: laser weapons, particle-beam weapons, and high-power microwave (HPM) or radio-

frequency (RF) weapons. EM launchers use electrical energy to throw a mass at a

target, thus making them distinct from directed energy. There are also three types of EM

launchers: rail guns, coil guns, and induction drivers. All involve the use of strong magnetic

fields to push against projectiles. While electric guns are an electric weapon, they

are not a DEW.

High electrical powers and large energies are needed for all these weapons. Technologies

for storing and controlling electric power are needed and are commonly called

pulsed-power technologies. Electric guns are often associated with DEWs due to their

common reliance on pulsed-power technology. The types of electric weapons are shown

in Figure 1.


Figure 1. Types of Electric Weapons




51


The Basics of Electric Weapons and

Pulsed-Power Technologies


There are a number of powerful advantages of

electric weapons over conventional explosives:

DEWs have a near-zero time of flight compared



to conventional ordnance, allowing

longer decision times and quicker reaction

times.

Electric weapons have a large “magazine” capacity,



often limited only by the ability of the

power source to recharge the system. The firing

rate depends on how fast the system can

be recharged, which in turn, depends on the

available power source.

The cost of engagement is greatly reduced.



With increasingly sophisticated conventional

weapons, the cost of practice rounds, such

as a missile, can be millions. For an electric

weapon, the cost per engagement is greatly

reduced, making the attack of small targets

(the asymmetric threat) less costly and training

much more affordable.

There is the potential for variable lethality,



where the weapon effects can be controlled

or attenuated to provide a warning or nonlethal

effect. Otherwise, a full-power setting

can be used to destroy the target.

Electric weapons have the benefit of increased



safety since less ordnance needs to

be stored. Logistics costs less, and underway

replenishment is easier since explosives are

reduced or eliminated.

Electric weapons can be used in conjunction



with conventional weapons to heighten

overall combat system effectiveness, such

as knocking out electronics before engaging

with a kinetic weapon.

Historically, the key Navy scenario for using

directed-energy technologies has been closein

protection of naval vessels from antiship cruise

missiles, particularly in a littoral environment. The

ability of a DEW’s speed-of-light engagement is

particularly attractive under conditions of short

warning times from supersonic stealthy missiles.

However, increasingly difficult and problematic

threats from nonmilitary aircraft and surface ships,

countersurveillance platforms, fast patrol boats,

unmanned aerial vehicles (UAVs), and terrorist inflatable

boats or jet skis present different challenges.

The threat has shifted from small numbers of

expensive targets in open water to large numbers

of small and cheap targets among neutral forces.

The unique characteristics offered by DEWs,

when compared to traditional weapon systems, allow

them to be applied across a spectrum of threat

roles, particularly in friendly or neutral-rich regions

where precision pointing or less-than-lethal

capability is paramount. The potential for HPM to

counter electronics at levels below human effects

makes them ideal nonlethal weapons. Electromagnetically

launched projectiles allow longer range,

shorter flight times, reduced reliance on air strikes

and missiles, and safer storage and replenishment.

With military budgets being squeezed, the low cost

of directed-energy engagements, which often require

just a few gallons of fuel, cannot be overemphasized.

Instead of million-dollar missile shots,

electric weapons allow new tactics, warning shots,

and continual fire against large and small targets.

They also allow inexpensive practice and training

for improved readiness.

Pulsed Power for Electric

Weapons

A useful rule of thumb is that a stick of TNT

contains about a megajoule (MJ) of chemical energy,

and this amount is often needed to destroy

a military target. To destroy a target with an electric

weapon, the electrical energy must also be deposited

quickly. Surprisingly, a candy bar also has a

megajoule of chemical energy, but it is released very

slowly when we eat it. Many electric weapons require

peak powers of more than a gigawatt (GW) or

energies more than a megajoule. The time scales for

delivery range from milliseconds to nanoseconds.

As an example, delivering 1 MJ of energy in 10 μs

requires 100 GW of power, which is more than a

commercial power plant can produce. It is not practical

to build continuous power supplies to directly

drive most electric weapons. Consequently, pulsedpower

technologies are needed to store energy at

low power rates and release it quickly for weapon

use. A pulsed-power system takes electrical power

from a prime source (like a motor), stores it, and

transforms the power to meet specific user requirements.

The importance of a pulsed-power system is

often underappreciated. For most electric weapon

systems, the system size, weight, volume, and reliability

are dominated by the pulsed-power chain.

Pulsed-power components must be improved

along with the weapon technology to make electric

weapons systems practical. A block diagram of

a pulsed-power system is shown in Figure 2.

Electrical energy can be stored in many ways,

such as a battery (actually a chemical storage). A

car battery has about a megajoule of energy, but

it takes many seconds to drain it. A much faster

method of storing electrical energy is in a capacitor,

which can be discharged in milliseconds or faster.

Inductive methods store the energy in the magnetic

fields of a coil. This has the potential of achieving

higher energy density than capacitors, but

52

Directed Energy


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when the supporting systems are considered, the

technology becomes less attractive. Energy storage

for electric weapons can also be done with chemical

explosive energy, where an explosive force is

converted into electrical energy using techniques

such as flux compression. Energy can be stored in

the inertia of rotating machines and flywheels, but

the energy can be released only as fast as the flywheel

or motor can be stopped, usually in seconds.

In many cases, several stages of energy store are

used where each stage is faster than the last. Once

the energy is stored, it must be released quickly using

a high-power switch. There are many types of

switches. Perhaps the most common type for electric-

weapon applications has been the spark gap.

Many types of controlled spark gaps exist, including

pin-triggered, laser-triggered, field distortion,

and simple overvolted. To achieve high repetition

rates, flowing oil or gas can be used to flush the hot

spark products, or sealed gaps using special fast-recovery

gases, such as hydrogen, can be employed.

Other switches, such as vacuum tubes and solidstate

switches, can be used if they can handle the

voltages and currents needed. Solid-state technologies,

such as thyristers, have become very capable

in recent years. Once the energy is switched

out, there is usually some additional power conditioning,

where transformers or pulse-forming networks

are used to provide the desired pulse shape,

voltage, and current required for the weapon. For

rapid firing rates or continuous use, high average

input powers are needed.

All-Electric Ship

One of the major impediments to the development

of electric weapons systems for Navy ships

has been a lack of electrical prime power. Current

surface combatant designs employ up to 90 percent

of engine power mechanically dedicated solely to

propulsion. These designs are unable to provide

the tens to hundreds of megawatts (MW) of electrical

power capacity required for many electric

weapons. The solution is an electric-drive ship that

uses all the engine power to generate electricity, enabling

it to allocate power to weapons or propulsion

as needed. In recent years, the Navy has been

investigating cost-effective power-system options

to meet future platform requirements.

High-Power Microwave (HPM)

and RF Weapons

Microwave weapons are generally considered

to use frequencies above a gigahertz, whereas lower

frequencies are generally called RF weapons.

These weapons are more powerful than electronic

warfare systems and are designed to create extended

disruption or permanent damage. An HPM

weapon is considered to have a peak power of more

than 100 MW, or energies above 1 J. The energy can

enter a target through intended RF paths, such as

target antennas (front door), or unintended paths,

such as housing joints, cavities, and circuit wires

(back door). Pulses ranging from a few nanoseconds

to microseconds in duration can be sufficient

to reset computers, cause loss of stored data, or

Figure 2. Block Diagram of a Pulsed-Power System




53


The Basics of Electric Weapons and

Pulsed-Power Technologies


cause microprocessors to switch operating modes.

Nonlinear circuits and components can rectify signals

and absorb energy outside of their normal operating

parameters. Figure 3 illustrates some of the

vulnerability areas on a missile body.

RF or HPM devices can be divided into narrowband

or wideband systems, dependent upon

the employed pulse length. Narrowband systems

are similar to high-power radar pulses and produce

RF radiation with a very narrow bandwidth (frequency

coverage). The damage concept is to create

enough energy in a target to overheat or overload

electronic components. Wideband systems generally

produce very short pulses (nanoseconds) and

typically operate in lower frequency ranges. Wideband

systems produce much lower average powers

and rely on high-peak electric fields to produce reset

or arcing of digital components. Creating short

pulses—often only a few RF cycles long—generates

a very broad frequency output to take advantage

of a target’s weak point. But, it also means that the

energy is spread over many frequencies, so there

may be very little energy at a specific vulnerable

frequency. Vulnerability data is critical to estimate

the effectiveness of HPM weapons. Ultimately, air

breakdown will limit the amount of energy out of

an antenna to around 1 MW/cm2.



HPM devices can produce effects that range

from denying the use of electronic-based equipment

to disrupting, damaging, or destroying such

equipment. HPM weapon advantages include allweather

capability, low precision pointing requirements,

and effects persistence after the radiated

EM energy “beam” has been turned off. One major

advantage of HPM is that electronics are generally

more vulnerable to high fields and high energies

than humans. This provides the ability to attack

electronics without harming people, which makes

HPM an ideal choice for nonlethal applications.

Two major challenges of implementing HPM

technologies into an operational weapon systems

platform are:

1. Fratricide, or self-destruction, can be a problem

because of the large areas affected by the

sidelobes and near field of any meaningful

HPM weapon system. Therefore, when

attacking a target of interest with an HPM

weapon, there is a greater risk of disruption

to systems that were not intended to be targeted

but fell within the sphere of influence.

Host platforms, therefore, may need to undergo

interference hardening.

2. With regard to battle damage assessment,

kinetic weapons have the advantage of typically

leaving visual evidence. HPM weapon

systems do not leave large holes in a target

but create more subtle influences as a result

of attacking critical electronic components.

Consequently, it can be more difficult to ascertain

whether a target’s capabilities have

been sufficiently degraded or destroyed—and for how long—n determining whether

a mission was successful.

For HPM system development, a fundamental

challenge is the understanding of what it takes to

affect the target. Coupling mechanisms, where EM

energy enters and affects the target system, are extremely

complex. The vulnerability of components

is often vastly different if it is outside or inside a circuit

board or enclosure. Effects depend upon the interactions

with other components, connectors, and

nearby conductors. The effects on a component can

vary many orders of magnitude depending on frequency,

orientation, cracks and seams, protective

circuits, pulse energy, and duration. Research regarding

effects on missiles has shown large variations

not only between designs, but also between

different serial numbers due to assembly methods,

cable routing, and component variations. With

the increasing use of commercial equipment by

the military, such as computers and radios, effects

are difficult to predict due to constant design and

component changes. In general, electronics are getting

smaller and operating at lower voltages, making

them more sensitive to high fields. But smaller

components often have lower pickup areas, and the

proliferation of interfering signals has increased the

amount of shielding on modern electronics. When

Figure 3. HPM Coupling Paths on Missile Body




54

Directed Energy


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target systems are located inside structures or buildings,

it becomes even more difficult to predict. Efforts

to predict reflections and interference inside

complex structures become extremely complicated.

Accordingly, generic electronics kill using universal

waveforms is not likely. There continues to be a lot

of hype about what RF weapons can do, but the idea

that a backpack device can wipe out all electronics

in a city is no more realistic than a hand-held laser

cutting through a bank vault door.

High-Energy Lasers (HELs)

A laser generally produces a beam of coherent

light at a specific wavelength dependent on

the atomic structure of the lasing substance. Only

certain substances have the atomic properties appropriate

for producing laser light, and these are

often limited in power. Lasers are characterized

by the substance being lased (gas, liquid, or solid)

and the “pumping” process (light energy, electricity,

or chemical reaction). A resonant optical cavity

provides the means for aligning the energy in

the beam and extracting that energy. A military laser

system also includes beam processing or beampath

conditioning, beam pointing and control

and—or long-range applications—daptive optics

to compensate for the atmosphere.

Until recently, HELs have been driven by chemical

energy, so very little electrical power or pulsed

power was needed. Chemical lasers use the reactions

of gases or liquids to create the excited energy

states necessary for laser emission. Large chemical

lasers and beam directors have been developed by

the Navy in recent decades and have successfully

ruptured fuel tanks and downed supersonic missiles.

However, these lasers required high-velocity,

chemical-reaction chambers and emitted hazardous

gaseous by-products. They often operated at

wavelengths where the atmosphere absorbed much

of the energy. Absorption creates thermal blooming,

whereby absorbed energy in the air creates

a negative lens that defocuses the beam. Increasing

the power of the laser increases the energy absorbed

and worsens the problem. The Army and

Air Force are developing chemical lasers for airborne

applications, where atmospheric absorption

is less of a problem. Recent Navy interest in HELs

has concentrated on lasers that are electrically powered,

rather than chemically powered, and that operate

at shorter wavelengths to allow smaller optics

and more efficient propagation near the water.

Small semiconductor (or diode) lasers use current

flow through an electrical junction to excite

electrons and create laser light. These lasers are

very limited in power, so research has focused on

using large numbers of lasers assembled into a coherent

array. Semiconductor lasers also create efficient

light to excite or “pump” other types of lasers.

Solid-state lasers (SSLs) use crystalline materials

mixed (doped) with elements needed for proper

lasing. SSLs show strong promise for compact, medium-

power HEL weapon systems. Scaling these

systems up to megawatt levels creates extreme heat

in the crystal material, making it very difficult to

prevent internal damage. Forced cooling and the

heat capacity of large masses are under study.

Fiber lasers—hich use semiconductor diode

lasers to pump a flexible, doped crystalline fiber

(similar to a fiber-optic line)—ave demonstrated

high efficiency and relatively high power. The technology

is being used in the welding and cutting industries.

Methods of pumping large numbers of

fiber-optic lasers and combining them are being investigated.

An example is shown in Figure 4.

The free-electron laser (FEL) operates differently

from a conventional laser. An FEL uses a

high-voltage electron accelerator to push electrons

through a magnetic “wiggler” to create light radiation

across a tunable band of frequencies. The FEL

is extremely complex and large, but scaling to very

high powers may be possible. Perhaps the biggest

promise of the FEL is the ability to design the laser

at an ideal atmospheric propagation wavelength.

Significant technical hurdles remain in reaching

the status of a deployable FEL, in scaling the beam

to megawatt powers and in providing the necessary

engineering to turn a laboratory device into a weapon

system of reasonable size. For Navy application,

FELs will require improvements in areas of radiation

shielding, high vacuum, high-current photoinjectors,

and probably cryogenic cooling—ll of

which must be integrated into a ship’s basic design.

Fiber lasers and SSLs are the leading-candidate

Navy lasers for medium power, as FELs are

for high power. All are electrically driven and can

meet the requirement for shorter wavelength, capable

of transmitting at the “maritime window” of

approximately 1 μ.

HEL weapons’ advantages include a highly directional

and narrowly focused beam, providing:

Minimal collateral damage

Speed-of-light delivery

Rapid retargeting

Low cost of engagement



Disadvantages center on:

Limited range due to atmospheric attenuation

Weather limitations

Low efficiency (often less than 10 percent)

Need for eye protection

Relatively large size and weight requirements




55


The Basics of Electric Weapons and

Pulsed-Power Technologies


Figure 4. Drawing of Laser Weapon System (LaWS)



Long dwell times (seconds) will be needed for

most targets. As with RF systems, there is a potential

nonlethal or variable lethality capability since the

energy can be easily defocused. A critical challenge

is the understanding of a laser beam’s propagation

through a maritime boundary layer environment,

where the sea and air interface creates turbulence

and moisture gradients. Measuring the atmosphere

and compensating for variations in real time may require

adaptive optics or “rubber mirrors” that can be

constantly adjusted to compensate for changes. Focusing

a small spot at long range will require high

beam quality and large optics, probably meter-size

mirrors that are very highly reflective and very clean.

HELs in the future are expected to be able to focus

energy to a spot size of much less than a meter

at ranges of kilometers. This will necessitate very

accurate target tracking systems, and precise stabilization

and beam-pointing systems, both of which

are difficult but should be feasible in the near term.

Real-time atmospheric measuring systems will be

needed for compensation techniques. Methods to

protect the sensitive optical system from salt spray

and corrosion will also be needed.

From a lethality perspective, three considerations

need to be better understood before a HEL

can be deemed a true weapon system:

1. Achievable spot size of beam on target at

range

2. Amount of coupling into the target material

3. Subsequent effects of the damage inflicted

For the more severe threats,

such as high-speed, antiship

cruise

missiles, HELs face the difficult

task of engaging maneuverable,

stealthy, inbound missiles. As

such, a better quantitative understanding

of the interactions

among a laser beam’s energy deposition,

target material, and

flight dynamics is needed.

Particle Beams

A particle-beam weapon is

a directed flow of atomic or subatomic

particles. These particles

can be neutral or electrically

charged. Neutral beams need to

be used outside the atmosphere

(in space), where charged particles

would repel and fly apart.

Charged-particle beams (CPBs)

are easier to make and are used

within the atmosphere, where

air molecules can constrain the

beam. A CPB weapon transmits matter—not just

EM waves—like lasers and microwave weapons.

The particles are near the speed of light and deposit

their kinetic energy deeply into any target material.

They have the potential to be highly destructive

weapons and are very difficult to shield against.

Charged particles are produced by applying a

strong electric field near a material that emits electrons.

These electrons then pass through accelerating

stages with high voltage gradients (often

megavolts), which increase the electron’s velocity.

As the electrons pass each stage, the velocity

increases until they approach the speed of light

(become relativistic), at which point they have substantial

energy to penetrate a target. The accelerating

systems can be linear, but a recirculating design

is more compact and can reuse stages. These systems

are basically high-current versions of scientific

particle accelerators.

Once the electron beam is produced, it must

propagate to the target. High-velocity electrons

will not go far before they collide with air molecules

and lose energy. The fact that air molecules

struck by the beam are heated and moved out of

the way for a short period of time creates a rarified

“hole” in the atmosphere through which a second

pulse can travel farther. In this manner, a fast series

of pulses can “hole-bore” to the target, each pulse

going farther than the last. The final pulse must

have enough energy to damage the target. The deceleration

of electrons in the atmosphere causes

56

Directed Energy


Technology, Modeling, and Assessment



Bremsstrahlung radiation in the forward direction

toward the target, creating gamma rays that, in

turn, create X-rays and RF radiation.a These effects



can cause electronic upset and “soft-kill” mechanisms

even if the beam slightly misses the target.

The beam of electrons is typically a few centimeters

in diameter. When a beam strikes a target,

the energy is deposited deep in the material (the

collision cross section is small because of the relativistic

speeds) in microseconds (much faster than a

laser), creating thermal shock that is very difficult to

shield against. For an explosive target, there is also

the possibility of causing a deflagration or low-order

burn, disrupting the normal warhead mechanism.

Scientists studying CPB weapons made significant

technical advancements in the 1980s, but

the weapons are still far from being practical. A

CPB weapon is technically very challenging and

expensive to build. Studies project that the volume

requirements necessary for a CPB system

could be on the order of a 5-inch gun system. Advantages

of a CPB weapon include rapid penetration,

a deep magazine, all-weather capability, and

soft-kill mechanisms for a near miss. Problems include

complexity, size, limited range, and the need

to demonstrate compact accelerators and propagation

mechanisms.

Electromagnetic (EM) Launchers

A number of technology concepts to launch

projectiles exist using electrical energy. These systems

rely on large currents in conductors, creating

strong magnetic fields that drive a projectile. The

velocity of a normal powder gun projectile is limited

by the expansion speed of the explosive powder,

and present military guns are reaching that limit.

With an electric gun, the fields can push projectiles

much faster, providing longer ranges and increased

kinetic energies. The simplest version is an EM rail

gun, shown in Figure 5.

In any conducting loop, the generated magnetic

field tries to expand the loop. If everything is held

in position, the only movable item is the conducting

projectile, which moves down the rails in an attempt

to expand the loop. Since megajouoles of projectile

energy are needed for EM rail guns, energy storage

Figure 5. Electromagnetic (EM) Rail Gun Concept




57


The Basics of Electric Weapons and

Pulsed-Power Technologies


mechanisms that can store about 100 MJ are needed,

along with the ability to discharge the energy in

milliseconds. To generate useful forces, millions of

amps of current are needed—a major challenge and

significant loss mechanism. Large capacitor banks

with very high-current switches are required. Spark

gap switches have historically been the only option,

but new high-current solid-state switches are now

becoming available. Capacitor energy densities, too,

have improved an order of magnitude in the last few

decades. Rotating machines have also been considered

because they are smaller than equivalent capacitor

banks, but extracting the energy quickly,

without tearing the machine apart, has been problematic.

The launch energy of various projectiles is

shown in Figure 6.

A rail gun is probably the most compact form

of electric launcher. However, it requires direct

electrical contact between the projectile and barrel

rails, creating the potential for arcing, melting, and

erosion. Coil guns use a series of sequentially fired

coils around a “barrel” to push the projectile in

stages. This does not require direct electrical contact,

so it avoids rail erosion but requires a series of

fast timed switches and more space. Linear induction

motors are basically unrolled electric motors

and have been used on electric trains and roller

coasters, typically with magnetic levitating systems

to avoid contact erosion. This concept is being developed

by the Navy for launching aircraft. The

energy to launch an aircraft is similar to a largecaliber

projectile—ore weight but less speed. The

slower speeds are more suitable for rotating machines

since the launch times are seconds rather

than microseconds.1 Electrothermal guns and electrothermal-



chemical (ETC) guns use a combination

of electricity and chemicals. Electrical energy

is used to initiate chemical reactions that can produce

lightweight driving gases, like steam, or allow

more energetic propellants that are difficult to ignite

in a conventional fashion.

Some advantages of electrically driven projectiles

include:

Higher projectile velocity (over conventional



explosives)

Very long range (>100 miles) with lower cost



than missiles

Time-critical delivery (because of shorter



time of flight)

Safer projectile stowage (minimal explosives)

Potentially adjustable velocity levels, for better



accuracy and controllable damage

The potential of having nonexplosive rounds

and magazines is very attractive for the Navy. For

long-range, large-caliber EM projectiles, the kinetic

energy from the projectile velocity is greater than

the chemical explosive energy in a conventional

round traveling much slower. Therefore, damage

can be equivalent even without explosives. System

size and lifetime are still behind conventional systems,

but getting close.

Outlook

Challenges remain for many electric weapon

concepts. These weapon systems appear promising

to meet the increasingly important asymmetric

threats with low-cost precision rounds. They

also can be employed across the energy spectrum

for nonlethal targeting. Electric weapon systems

will, in many cases, continue to supplement existing

kinetic weapon systems in the near term. Despite

technology challenges, directed-energy and

electric weapons hold great promise in offering the

future warfighter unique combat capabilities not

currently available.

Endnote

a. Bremsstrahlung—a type of radiation emitted when high-energy

electrons are decelerated. (German for braking radiation)



Reference

1. Shope, S. et al., Long-Range Naval Fire Support with a Coilgun,



Sandia Report 2001-3832, February 2002.

58


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Technology, Modeling, and Assessment



Solid Modeling of Directed-Energy Systems


By Joseph F. Sharrow



Not long ago, around the mid-1980s, development of most new mechanical systems—

such as automobiles, consumer products, and military devices—was performed

manually on a drafting table or drawing board, much like the present-day version shown

in Figure 1. These tables and boards performed a necessary function, but they offered

little assistance other than for drawing lines. Engineers used them to prepare layouts, or

two-dimensional sketches of what they were designing. They then would take these layouts

to a draftsman, who would create drawings of each part in the device. The drawings

would subsequently be sent to a manufacturing facility.

This layout and drawing preparation process typically would need to be repeated

multiple times because mistakes would be made, or design issues would be discovered

late in the process. Similarly, the manufacturing process would sometimes require multiple

iterations as well because of the inherent limitations in designing three-dimensional

(3-D) devices on two-dimensional boards. This less-than-ideal process made it

difficult to design and manufacture even mundane products and frequently resulted in

things that just didn’t work. With the emergence of early computerization, numerical

analyses of more complex systems began to be performed. These analyses were conducted

to ensure that the systems worked in the real world. For example, engineers might

conduct a structural analysis of the forces in a loaded dump-truck bed to make sure that

the frame wouldn’t bend and fail. Because of the difficulty in performing these analyses,

they would often require a specially trained group of structural engineers, expensive

software, and large mainframe computers, limiting their use to only the largest, most

well-funded companies or organizations.


Emergence of Computer-Aided Design (CAD)

and Solid Modeling

With the availability of smaller scale computers and more economical software in

the mid-to-late 1980s, CAD was born, initiating a period of rapid improvement in the

design process. This was driven, in part, by the introduction of software packages such

as AutoCAD. Initially, these software packages only attempted to automate drawing

lines by making wireframe (stick-figure) versions on the computer of what previously

had been made by hand on the drafting board. This reduced the difficulty in making

changes in the development process, but it still limited the engineer’s pallet to a two-dimensional

space. What was really needed was a 3-D method of design. Solid modeling


59


Solid Modeling of Directed-Energy Systems


addressed this need beginning in the late 1980s to

early 1990s.

Solid modeling is analogous to taking blocks of

clay and cutting and forming them into the shape

of a solid part on a computer. These 3-D parts are

then put together in an assembly, more accurately

representing real-world devices. Though originally

used only in a limited way for specialized applications

in the aircraft and automobile industries,

it wasn’t until the 1990s that solid modeling experienced

widespread availability and mainstream

acceptance due to software packages such as Pro/

ENGINEER. Figure 2 summarizes how Pro/ENGINEER

and other similar packages fit into the development

of new products. The general flow of the

process moves from left to right.

Initially, nearly all 3-D solid modeling packages

required significant computing and graphics

display power, necessitating the use of large graphics

workstations running the UNIX operating system.

Rapid advances in computing and graphics

power have since enabled nearly all packages to

run efficiently on personal computers (PCs) and

laptops, bringing solid modeling and analysis capability

into the mainstream.

Figure 1. Drawing Board

Figure 2. Solid Modeling in the Development Process




60

Directed Energy


Technology, Modeling, and Assessment



Solid Modeling of

Directed-Energy Systems

Engineers working in the Directed Energy

Division at the Naval Surface Warfare Center,

Dahlgren Division (NSWCDD), use solid modeling

to develop hardware for nearly all of its programs.

Both Pro/ENGINEER and SolidWorks are

used extensively to develop new products in virtual

3-D space. Additionally, the structural simulation

package within Pro/ENGINEER is used to determine

stresses and natural frequencies of parts and

assemblies. Consequently, these packages have enabled

a single mechanical engineer in the Directed

Energy Division and a draftsman in the Engagement

Systems Department at Dahlgren to perform

the design and analysis work that would have required

an entire group of engineers and draftsmen

just a few years ago. Today, collaboration among

many organizations using similar packages has become

commonplace. Insofar as solid modeling has

become an indispensable tool for development and

collaboration, its successful implementation requires

proper training and experience before engineers

can use it effectively, just as medical surgeons

require training in the use of advanced robotic surgical

devices before they can be used effectively.

Thus, while these high-tech modeling systems not

only have reduced the number of personnel needed

for design and development, they have enabled

the Navy to get significantly more bang for its buck

while supporting warfighting needs. An example of

how solid modeling is currently being used is discussed

below.

Navy Laser Weapon System

(LaWS) Beam Director

The Directed Energy Warfare Office (DEWO)

and Directed Energy Division at Dahlgren are currently

developing the Navy LaWS for the Naval Sea

Systems Command’s Directed Energy and Electric

Weapon Systems (DE&EWS) Program Office (PMS

405). The program’s goal is to take advantage of currently

available industrial laser technology and incorporate

it into a future naval weapon system. As

part of the development process, major subsystems

have been integrated with a Kineto Tracking Mount

(KTM) into a LaWS beam director. The KTM/beam

director was modeled and analyzed using Pro/ENGINEER.

Ultimately, the resulting LaWS will be

installed on Navy ships on the Close-In Weapon

System (CIWS) gun mount. During field testing in

June 2009 at the Naval Air Warfare Center, China

Lake, California, the prototype KTM/beam director

successfully destroyed five unmanned aerial vehicles

(UAVs). The actual beam director used in the

China Lake testing is shown in Figure 3; the Pro/

ENGINEER assembly model used for development

is shown in Figure 4.

The LaWS effort took advantage of many aspects

of solid modeling including collaboration,

structural and modal analysis, and manufacturing

drawing creation. The project required development

of new, unique hardware, as well as the

integration of electronic models from commercial

vendors. The KTM model was provided by L-3

Brashear and was originally designed using Pro/

ENGINEER. The beam-directing telescope model

was provided by RC Optical Systems, Incorporated,

and was originally made in SolidWorks.

These models were combined with many new optical

and structural components developed by the

Directed Energy Division into a single, comprehensive

assembly model. This model was instrumental

in understanding the interaction of the

many components, and its use increased accuracy

and precision that would have been impossible

with old-fashioned two-dimensional development

processes. Figure 5 shows a cross section

through the main portion of the beam director,

revealing the complexity of the many parts and

subassemblies required for such a device. In addition

to modeling the mechanical components, the

actual laser beams were also included to better understand

their path through the various mirrors

and optical devices in the beam director, and to

better highlight any interference they might have

with structural components within the KTM or

telescope.

Numerous analyses were performed to make

sure that everything worked the way it was intended.

One major analysis addressed the telescope

mount. To ensure that the beams were stable at

range, the mount had to be extremely stiff. The best

way to ensure this was to perform a structural analysis

using the structural simulation package within

Pro/ENGINEER. Figure 6 shows the results of that

analysis: a displacement plot in which different colors

represent how much the telescope will move

when the KTM rotates at its maximum speed. The

large cylindrical object simulates the mass of the

telescope. The minimum amount of displacement

is indicated by blue, and the maximum is shown

in red. This analysis verified that the movement of

the telescope, relative to the optical components

within the optics breadboard, was acceptable and

should perform well at the range specified by the

program office.

After modeling and analysis were completed,

manufacturing drawings of custom parts were created

by the Engagement Systems Department to be

61


Solid Modeling of Directed-Energy Systems


Figure 3. LaWS Beam Director

Figure 4. LaWS Beam Director Assembly Model




62

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Technology, Modeling, and Assessment



Figure 5. LaWS Beam Director Cutaway

Figure 6. Displacement Plot




63


Solid Modeling of Directed-Energy Systems


sent to manufacturing facilities, such as machine

shops. One example is shown in Figure 7, which

shows the first sheet of the multisheet drawing

needed to manufacture the large plates that support

the telescope from the center platform of the

KTM. One of these plates is also shown in the displacement

plot in Figure 6.

Even though it would be possible for one person

to do all of the modeling, analyses, and drawings for

a particular program, a more efficient process takes

advantage of using the best skills available by collaborating

with other experts. Collaboration enables

assembly, part, and drawing files to be sent

electronically, eliminating the need for collocating

personnel. Drawings for the LaWS program, for instance,

were made using noncollocated personnel

across base at NSWCDD. They could just as easily

have been made using personnel from across the

country.

The LaWS program exemplifies how the Directed

Energy Division uses solid modeling to

enhance the quality and effectiveness of Navy directed-

energy capabilities. As a result, warfighters

will be better armed with more effective weapons

and capabilities for future naval conflicts.

Acknowledgment

The author would like to acknowledge the

valuable contributions of the Engagement Systems

Department’s drafting group in support of

numerous DEWO and Directed Energy Division

programs.

Figure 7. Manufacturing Drawing





64


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Technology, Modeling, and Assessment



A Fundamental Key to Next-Generation

Directed-Energy Systems


By Directed Energy Division, Electromagnetic and Sensor Systems Department



Imagine an explosive ordnance disposal (EOD) unit on a routine scouting patrol

deep in the notorious “Triangle of Death” south of Baghdad, where Marines, Sailors,

and Soldiers frequently find themselves exposed to improvised explosive devices (IEDs).

Fortunately, this newly outfitted unit is equipped with the latest unmanned, mobile, remote-

controlled, radio frequency (RF) transmitter used as a directed-energy weapon

(DEW). The integrated system provides comprehensive IED prediction, detection, prevention,

and neutralization capabilities. Lightweight, pocket-sized transmitters carried

by each warfighter constantly communicate sensor intelligence, key vital signs, critical

conditions, and location telemetry to a geostationary satellite (GEOSAT). It intercepts,

collects, and retransmits intelligence and situational awareness data simultaneously to

any command post in the world and to each member of the unit on patrol. Highly efficient,

miniature, switch-mode, RF amplifiers with high-power density (small size and

weight with high-power output) enable these visions of future capabilities as their systems’

transmitter backbone.

To civilians, the miniaturization of modern wireless (electromagnetic) devices is

considered a mere convenience or luxury, i.e., Blackberries, mobile phones, and highspeed

wireless network connections. To the next-generation warfighter, miniaturized,

wireless, directed-energy (DE) systems open the door to the realization of a whole new

set of effective and efficient wireless modalities. And while the capabilities mentioned

in the above scenario are not yet available to warfighters, researchers believe they have

uncovered the key to next-generation DE systems leading to the miniaturization of

DE devices.


Next-Generation DE System Requirements

At the Naval Surface Warfare Center, Dahlgren Division (NSWCDD), key system

requirements for effective next-generation DE systems are being researched and developed

for applications to counter IEDs, to detect explosively formed penetrators (EFPs),

to neutralize explosives, and to predict threat locations. Next-generation DE systems

must yield a high probability of mission success and be inherently safe to operate. By

design, they must minimize or eliminate the risk of hostile attack or collateral damage

especially during screening missions. Considering the DEW example above, practical


65


A Fundamental Key to Next-Generation

Directed-Energy Systems


next-generation DE systems must be physically

characterized by:

Low mass (weight)

Small size (volume)

High-power output with respect to size or



high-power density

High efficiency for extended mission use

Minimized prime power and cooling support

Portability

Mobility

Configurability



They must also ensure a high probability of mission

effectiveness. The DEW must be easily transportable

and agile, adapting to the immediate, local

military mission requirements in various warfighting

environments. Additionally, DE systems must

be mechanically robust and able to withstand the

shock and vibration of combat missions in rough

and rugged environments. The key requirement—

efficiency—fundamentally facilitates all required

characteristics, including mass and size.

Moving Beyond Requirements

Scientists at NSWCDD, sponsored by the Office

of Naval Research (ONR), are researching and

developing key system requirements for effective

next-generation DE systems to counter IEDs, to

detect EFPs, to neutralize explosives, and to predict

threat locations.

Researchers at NSWCDD are leading the way

toward realizing small, lightweight, RF transmitters

using high-power, solid-state, switch-mode

amplifiers, theoretically 100 percent efficient. These

practical switch-mode amplifier realizations are

at least 1/100 the volume and weight of any commercially

available linear solid-state amplifier of

comparable power output. The challenges included

assessing what type of active amplifier device

and operation would provide the greatest power

density (power output per unit volume and mass)

with its necessary auxiliary systems, such as prime

power generation and cooling of waste heat. Such

a device also needed to provide sufficient output

power based on required standoff range and IED

system-coupling efficiency while also maintaining

a manageably-sized, easily transportable system.

Researchers initially considered tube-based systems,

but large, heavy, direct-current (DC) power

supplies are required, and typically 40 percent of

the input power is dissipated in heat, which negates

any possibility of miniaturization.

Upon a practical review of amplifier-class operations

and suitable active amplifier devices, however,

research pointed to contemporary switch-mode

080102-N-1132M-006 SHEIK SA’ID, Iraq (2 January 2008) U.S. Army Soldiers attached to 3rd Squadron, 2nd

Cavalry Regiment patrol and search for weapons or Improvised Explosive Devices (IEDs) during a clearing

mission. (U.S. Navy photo by Mass Communication Specialist 1st Class Sean Mulligan/Released)

66

Directed Energy


Technology, Modeling, and Assessment



amplifier schemes (e.g., Class-E and Class-F) using

solid-state technology—such as the high-electron

mobility transistor (HEMT)—as satisfying

the high-power density and abusive mechanical

requirements for expected worst-case transportation

and operation in a rugged environment. To

significantly impact reduction of size and weight,

practical, high-efficiency thresholds were defined

for next-generation DE systems at 90 percent and

greater. The key technology enabler to realize amplifier

high efficiency in high-power amplifiers

up to 60 kW was found in exploiting contemporary

switch-mode amplifier architecture with efficient

power combining. Particularly, switch-mode

schemes in Class-E and Class-F operation as solid-

state, active-hybrid planar topology designs

were found to be necessary and sufficient for DE

applications. These analyses led to a novel, Class‑E

RF switch-mode amplifier design. A Class-E RF

switch-mode amplifier can theoretically operate

at 100-percent efficiency. For every input watt

supplied, an RF output watt is produced. The conductors

and dielectric substrate of the hybrid planar

load network and the commercial off-the-shelf

(COTS) transistor all exhibit some small degree of

power loss, suggesting an estimated practically realized

efficiency of 90 percent.

Moreover, the amplifier under research consisted

of a novel microwave load network operating

with high-power output at ultrahigh frequency

(UHF). This research led to the state of the art in

Class-E designs leading by hundreds of watts, several

hundred megahertz in frequency, and roughly 10

percentage points in efficiency. A common, solidstate,

high-power amplifier design technique sums

the phase and amplitude of smaller amplifier units

to the large values required for DE systems. A practical

hardware limitation exists that limits the theoretically

infinite number of fixed RF output power

units to a finite number. Approximately 60‑kW

RF output power sets the boundary as the largest

hardware realization. By applying spatial power

combining in the propagating medium, phasedarray

antennas can be employed with constructive

wave interference in air that would allow sufficient

RF power densities on target, based on the number

of elements in the array. This technique eliminates

the traditional hardware necessary to power combine

the smaller power-amplifier elements, realizing

a much simplified DE system with enhanced

power density in the transmitter, and reduced mass

and volume.

The key to ultrahigh efficiency in a switchmode

amplifier, such as Class-E or Class-F, is found

in zero-voltage switching (ZVS). Here, the load

network is not only designed to be resonant at and

around a particular desired switching frequency, it

must simultaneously act to force the voltage across

the switch to be zero when current flows and when

it switches off; hence, theory suggests that no power

is dissipated because the product of current

through, and voltage across, the switch is zero.

It is this aspect of the design that makes the job

of switch-mode amplifier realization difficult. Of

course, in practice, a small voltage exists for a very

short time during the switching action, resulting

in a small amount of input power being dissipated

in heat. This theoretical description also assumes

that all components are ideal (i.e., no impedance

to current flow exists in the switch when turned

on). All realistic switches exhibit finite impedance

when turned on, which does dissipate some wasted

energy, but again, this is very small in modern

HEMT devices using the ZVS technique.

Class-E switch-mode amplifier theory development

began in the United States during the

1960s, with details published in 1975, although

some earlier reports were published in Russia.

Lumped element electrical components (RF choke

inductors and metal film capacitors) were initially

used in lower frequency (3 to 30 MHz) prototypes.

As engineers attempted higher frequency

designs in the very high frequency (VHF) range,

solid-state transistor switch parasitic intrinsic and

packaging elements found inside the transistor began

to be used as some of the key components necessary

for ZVS. These parasitic elements included

stray capacitance caused by differences of potential

between parts inside the transistor and inductance

caused by bond wire length that is used to

connect the transistor to accessible terminals in its

packaging. At microwave frequencies, these parasitic

elements become sensitive, invoking unintended

significant changes to load networks

designed to operate with the transistors. Intrinsic

elements include drain-to-source breakdown voltage

capability and peak current capability. As the

need for higher frequency operation and higher

power increased, constraints of key transistor parameters

became difficult to produce in traditional

silicon technology:

High instantaneous transient (peak) current



capability through the transistor

Moderate breakdown potential across the



transistor

Low output capacitance



Only within the past few years have transistor

manufacturers produced COTS transistors that

meet the required capabilities necessary to operate

in switch mode for microwave frequencies and

67


A Fundamental Key to Next-Generation

Directed-Energy Systems


081107-N-1120L-072 RAMADI, Iraq (7 November 2008) Joint EOD Rapid Response Vehicles (JERRVs) assigned to Naval Mobile

Construction Battalion (NMCB) 7’s convoy security element are secured following an escort mission from a forward operating

base. The Cougar-type JERRVs are employed by coalition forces for escort and logistics missions, and to protect personnel from

IEDs. NMCB 7 is deployed to U.S. Forces Central Command to provide contingency construction support to coalition forces in support

of Operations Enduring Freedom and Iraqi Freedom. (U.S. Navy photo by Mass Communication Specialist 2nd Class Michael B.

Lavender/Released)

high-power output. Selection is still somewhat limited

for designers.

New transistor technology known as gallium

nitride (GaN) HEMTs—using state-of-theart

manufacturing processes with GaN on silicon

carbide materials—now facilitates Class-E highpower

amplifier (100-W) designs at ultrahigh frequencies.

The design process for switch-mode

amplifiers is radically different than linear amplifiers,

so engineers have tended to continue using linear

amplifier design techniques due to familiarity,

rather than advance to the switch-mode designs.

Today, the Class-E and Class-F unit power output

(greater than 100 W) capability and upper frequency

limitation is based on a lack of available HEMTs

with the necessary parameter capabilities.

Most recently, transistor manufacturers have

limited their investment in the Class-E amplifier solid-

state switch market due to no commercial market

mandate. An assortment of presently available

HEMTs provides a low-power capability in terms of

1- to 10-W output power for Class-E amplifiers in

the cell phone market. The need remains to continue

advancing in commercially manufactured HEMTs

with key capabilities necessary to realize larger unit

power output, hundreds of watts to a thousand

watts, for practical implementation in DE systems.

Possible Multiple Applications

Directed-Energy Weapon Systems



Expanding on the vision of the next-generation

DEW system mentioned at the beginning of

this article, further imagine that EOD scouts detect

a laser fluorescence signature of C4 high explosive

and chlorine outgasses in the vicinity of an

abandoned vehicle 2-km north of their current position.

An electronic support measure (ESM) team

on board an approaching clearing vehicle initiates

RF jamming and electromagnetic surveillance procedures.

Electronic specialists also scan the area

with ground-surface differential thermography—

particularly to detect possible buried IEDs and

EFPs or their tiny command wires, crush wires, or

pressure plates—while clearing a pathway to the

abandoned roadside vehicle.

Directed


68

Directed Energy


Technology, Modeling, and Assessment



Upon arrival at a 500-m safe distance, the EOD

specialists command the RF transmitter’s robotic

platform, also equipped with sensitive gamma-ray

planar and computed tomography (CT) imaging

to navigate toward and around the vehicle, interrogating

every possible hiding place. It discloses

an IED in the fuel tank. The specialist lifts the

transmitter arming safety and commands the remote

transmitter to radiate a prescribed dose of

RF energy directed at a carefully chosen component

of the vehicle-borne IED (VBIED) system.

Without entering the vehicle, the advanced

screening system detects and defuses the deadly

IED buried within the rusty, metal vehicle chassis.

Within minutes, the suspected VBIED threat

is entirely neutralized, with absolutely no wounded

warfighters or casualties.

Mobile Ad-Hoc Wireless Network (MANET)



Beyond IED detection and neutralization,

imagine an expeditionary unit on patrol, with each

member equipped with an RF transceiver about

the size and weight of a cigarette pack with an ultrahigh-

efficient switch-mode amplifier. The miniature

transceiver constantly communicates sensor

intelligence, key vital signs, critical conditions,

and location telemetry to a GEOSAT. This small

switch-mode amplifier has the needed output

power to reach an altitude of 35786 km, where the

GEOSAT intercepts, collects, and retransmits this

intelligence and situational awareness data to any

command post in the world and to each member

of the unit on patrol simultaneously. The expeditionary

unit, spread out over a wide area with large

interspacing, shares the situational awareness and

intelligence data of each other at the speed of light.

Thus, near real-time, worldwide communications

with ubiquitous secure access from the battlefield

is possible in a multiple-input, multiple-output

(MIMO) architecture. The same system could provide

a soldier-to-soldier MANET.

Next-generation switch-mode RF amplifier

designs could also optimize payload weight and

volume on board new communication satellites

while supplying higher power density and making

efficient use of the solar power supply budget.

Improved switch-mode amplifier power output,

when combined with enhanced antenna design,

would minimize Earth-station antenna size requirements.

The recently launched satellite shown

at left demonstrates an example of the latest antenna

technology.

Looking Forward

Miniaturizing next-generation DE systems

opens up a whole new world of applications to support

warfighters in ways unimaginable just a few

years ago. Reduction of transmitter mass and volume,

accompanied with high efficiency, creates a

welcome trickle-down effect. Low profile, small,

lightweight DE systems means:

Less vulnerability to attack

Greater mobility and maneuverability

Simplified logistics with less fuel-supply demands

Less impact on the environment



Clandestine operations, too, could be executed

with greater ease and simplified logistics support.

In the case of MIMO MANETs, miniaturized

high-power density transmitters could further expand

capabilities for the warfighter, enabling them

to carry high-power transmitters to communicate

with satellites or other supporting platforms. The

Pictured here is the National Aeronautics and Space Administration

/ National Oceanic and Atmospheric Administration (NASA/

NOAA) Geostationary Operational Environmental Satellite-P

(GOES-P) launching from Cape Canaveral Air Force Station,

Florida, aboard a Delta IV rocket procured by Boeing Launch

Services on 4 March 2010. Built by Boeing Space and Intelligence

Systems, GOES-P will provide NOAA and NASA scientists

with data to support weather, solar, and space operations,

and will enable future science improvements in weather prediction

and remote sensing. Additionally, GOES-P will provide data

on global climate changes and capability for search and rescue.

69


A Fundamental Key to Next-Generation

Directed-Energy Systems


satellite industry itself could benefit from miniaturized

switch-mode amplifiers with much higher

power density microwave transmitters, resulting

in reduced payload mass and volume; this also reduces

Earth-station antenna gain and size requirements.

Conclusion

NSWCDD is meeting the demanding requirements

of next-generation DE systems with Class‑E

RF transmitter switch-mode amplifiers designed to

operate at ultrahigh efficiency, greater than 90 percent.

Having discovered the key to next-generation

DE systems, researchers at NSWCDD are focusing

on the urgent need to counter IED systems with

small, lightweight, highly efficient transmitters that

use switch-mode amplifiers. Considering the multiplicity

of additional applications, all advancements

made in amplifier counter-IED applications

can be transferred to other applications in the future.

Accordingly, while the capabilities suggested

in this article might seem somewhat far-fetched, in

reality, they are realizable in the near term. It is projected

that NSWCDD will soon have its first 250‑W

UHF amplifier unit prototype ready. These units

will fit in the palm of an average-sized adult’s hand

and can be power combined to the level necessary

for platform and mission requirements. A fully realized,

fieldable DEW system prototype is possible

in just a few years.

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Active Denial Array


By Randy Woods and Matthew Ketner



Active Denial Technology (ADT)—which encompasses the use of millimeter waves

as a directed-energy, nonlethal, counterpersonnel weapon—has the potential to provide

an important new escalation-of-force capability to U.S. operating forces. ADT projects

a focused beam of 95-GHz millimeter waves to induce an intolerable heating sensation

on an adversary’s skin, repelling the individual with minimal risk of injury. More than a

decade of research has established the biological and behavioral effects of ADT for large

spot size systems, such as Active Denial System 1 (Figure 1). While the effects of this

large spot size system have been successfully established, the technology that produces

those effects has the potential to progress in a number of ways, particularly with the development

of smaller, lighter, and lower-cost systems.

One research effort focuses on the development of smaller, lighter, and lower cost

ADT demonstrators that produce commensurate “ADS-effects,” with effective spot size

and power densities on target. In support of this effort, the Joint Non-Lethal Weapons

Program (JNLWP) sponsored the Naval Surface Warfare Center, Dahlgren Division

(NSWCDD) to develop a “smart target system,” which measures the millimeter-wave

beam using fast-response, 95-GHz diode detectors. NSWCDD subsequently developed

and tested the W-Band Beam Diagnostic Array to characterize the system’s beam with a

temporal resolution of 30 Hz and a high spatial resolution of 1 inch.

The current method of measuring the 95-GHz beam is to use carbon-loaded Teflon

(CLT) to produce an average power beam image. This method works as the CLT is exposed

to the system’s beam. The material heats, over a period of seconds, proportional to

the magnitude of the radio frequency (RF) field, resulting in an image as shown in Figure

2. After the exposure, the specific heat capacity of the CLT can be used with the temperature

increase in the CLT to provide an indication of the total energy deposited in the

material. This method produces a good representation of the average RF field; however,

any peak variations in the beam are averaged out.

To allow for high temporal-resolution measurements of the 95-GHz beam, a highdensity,

95-GHz diode-detector array was commissioned by the Joint Non-Lethal Weapons

Directorate (JNLWD), and was designed and built by NSWCDD, with support from

Millitech, Inc. The array consists of a center 11 × 11 matrix (shown in Figure 3) with four

removable arms that can be attached (shown in Figure 4), resulting in a measurement

area of approximately 1 × 1 m.


71


Active Denial Array


Figure 2. CLT Representation of Small, 95-GHz Spot



Each element’s profile consists of the individual

horn antenna from the array, an attenuator,

a detector, and a SubMiniature version A (SMA)

connection to the digitizer circuitry.

This configuration allows for the

power received from the antenna

to be attenuated and converted to a

direct current (DC) output capable

of being measured by an analog-todigital

converter. The machined antenna

elements provide a uniform

effective area for each element, allowing

field strength (W/cm2) to be



converted into power received (W

or dBm). The aperture antennas

also provide an impedance match

between free space and the waveguide

system. A cross-sectional

view of the array element is shown

in Figure 5, followed by a signal

flow diagram shown in Figure 6.

The basic principle of operation

behind the array is that the derivative

of the diode detector’s power

vs. output voltage curve is very

repeatable between detector elements. Therefore,

when the detector elements arrived at NSWCDD,

each detector element was paired with a variable

Figure 1. Active Denial System 1




72

Directed Energy


Technology, Modeling, and Assessment



attenuator and calibrated as a single unit. The calibration

was accomplished by inserting a known

input power of +5 dBm into the input of the attenuator

and setting the DC output voltage at a predetermined

millivolt (mV) output. This allowed the

detector’s individual offset voltages to be removed

and caused the detectors to behave in a repeatable

manner. The attenuator is able to be adjusted by

varying the depth that the aluminum nickel card is

inserted into the section of waveguide.

The final section of the electrical system converts

the DC voltage output from the detectors to

a digital signal to send back to the operator station.

For this, it was determined that a 16-bit digitizer

would be required to enable measuring the

microvolts output by the detectors on the low end

of their range, while still allowing the digitizer to

measure the full output voltage of 1.8 V for highinput

powers. Also, due to the proximity of the

operator to the array and overall system flexibility,

it was determined that Ethernet communications

would provide a sufficient means of reading

the system data.

To display the data to the operator, a two-dimensional

array is populated and displayed for the

user (shown in Figure 7). This allows values to be

Figure 3. Main Array Face

Figure 4. Full W-Band Array

Figure 5. Cross-Sectional View of Array Element




73


Active Denial Array


read directly from the display corresponding to the

watts per centimeter squared (W/cm2) present at



the array face. Data also is recorded so that it can be

viewed later in a player application, such as a video

file, or it can be viewed in a spreadsheet application,

frame by frame. The data shown in Figure 7

is representative of small-source testing performed

recently and very clearly shows the beam profile.

Conclusion

NSWCDD engineers successfully met the

W‑band array’s design goals of providing a high

temporal-resolution image of 95-GHz beams. The

system has been tested against two active denial

systems, providing good agreement with the

currently accepted methods, as well as valuable

information regarding the system’s beam characteristics.

These accomplishments will allow future

system development to take advantage of this better

understanding to possibly reduce system size

and increase the effective range. A better understanding

of the 95-GHz beam helps to facilitate

future ADT development for this much-needed,

nonlethal escalation-of-force capability for U.S.

warfighters, homeland defenders, and law enforcement

personnel.

Figure 7. Array’s Operator Interface Showing a Small Spot Source

Figure 6. Signal Flow Diagram





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Technology, Modeling, and Assessment



Directed Energy in the Military Environment


By LT Leedjia Svec, Jeremy Beer, and Dave Freeman


75


Directed Energy in the Military Environment


The military operates in the land, air, and maritime

environments. In each of these environments,

lasers and laser devices are increasingly being seen

and used in a variety of ways. Accordingly, the

military must protect itself and civilians from the

potentially dangerous effects of lasers and other directed-

energy devices.

Lasers are being used on the ground to determine

the intentions of people who approach

checkpoints and to dissuade aircraft from entering

restricted airspace. Laser weapons are also being

developed for use in the maritime environment.

With the use of lasers comes the requirement for

eye protection. The eye is particularly sensitive to

lasers and its anatomy includes optical components

that amplify the power of incoming light. Consequently,

the potential for injury or blinding is great.

Naval Medical Research Unit – San Antonio

(NAMRU-SA) is poised to lead the way in researching

and testing laser glare devices and laser

eye protection. The mission of the NAMRU-SA

is to conduct medical, dental, and directed-energy

biomedical research, which focuses on ways to

enhance the health, safety, performance, and operational

readiness of Navy and Marine Corps personnel,

and addresses their emergent medical and

dental problems in routine and combat operations.

NAMRU-SA was officially commissioned on

6 May 2009 and is a subordinate command under

the Naval Medical Research Center (NMRC) in Silver

Spring, Maryland, reporting to Navy Medicine

Support Command (NMSC) in Jacksonville, Florida.

NAMRU-SA consolidates the Naval Health

Research Center Detachment Directed Energy

Bioeffects Laboratory, the Naval Institute for Dental

and Biomedical Research in Great Lakes, and

the NMRC Combat Casualty Care research function.

As part of the Base Realignment and Closure

(BRAC) 2005, NAMRU-SA has moved to Fort

Sam Houston. Two new buildings that have been

constructed are the Battlefield Health and Trauma

Research Institute and the Tri Service Research

Laboratory. A conceptual drawing of the NAMRUSA

Tri-Service Research Laboratory (to house directed-

energy research) is shown in Figure 1.

Many factors must be considered when lasers

operate in military environments. On the ground,

lasers offer a greater likelihood of close contact exposure.

In aviation and maritime environments,

the mobility of lasers is limited to permanent fixtures

on aircraft or ships, so target acquisition can

be much more complicated. Often ignored, but just

as important and common to all environments, are

the psychological factors that need to be explored.

These factors include clarifying intentions, communications,

and effectiveness. In certain situations,

Figure 1. Naval Medical Research Unit – San Antonio Tri-Service Research Laboratory at



Fort Sam Houston, San Antonio, Texas (artist’s concept)

76

Directed Energy


Technology, Modeling, and Assessment



sometimes lasers are coupled with other modalities,

such as auditory instructions.

On the ground, laser exposure has been shown

to interfere with driving vehicles, making color

judgments, and target shooting. In aviation, lasers

can interfere with pilot vision, causing afterimages,

glare, or temporary ocular injury, with attendant

effects on navigation and control. In the maritime

environment, lights frequently are used to signal a

variety of messages, from direction (left, right, etc.)

to more complicated messages such as “man overboard.”

More prolific use of lasers underscores the

need for laser eye protection, a dynamic area of

research, which must respond to changing threat

wavelengths and changing environments. Figure 2

shows NAMRU-SA personnel executing an operational

field test at Kennedy Space Center, July 2009.

Recent studies undertaken by NAMRU-SA

have investigated the use of laser dazzlers on sailors

in small boats.a In these studies, participants



were exposed to the laser glare at different angles

and distances, in both day and night conditions.

Study protocols were approved in accordance with

the Institutional Review Board in compliance with

all applicable federal regulations governing the protection

of human subjects. Participants were given a

survey assessing their subjective response to the laser,

as well as a more objective visual eye chart. The

Figure 2. NAMRU-SA personnel execute operational field test at Kennedy Space Center, July 2009, in



which a nonlethal laser prototype is evaluated for power delivery (stability and beam propagation) at range

and human visual effectiveness aboard a maritime target.

77


Directed Energy in the Military Environment


results suggested that participants were

most affected by the laser at night when

they were looking straight at it (as opposed

to many degrees away) and at the closest

exposure distances. The most surprising

finding, however, was that some participants

reported being drawn to the laser

rather than away from it, especially at farther

distances. Participants remarked that

they couldn’t tell what the signal was, so

they would want to go closer to find out.

This illustrates that the assumption (by

some)—hat distant laser lights will deter

and repel innocent mariners—ight not

always be true. Further research is needed

to verify this finding, however, before employing

laser glare devices in the maritime

environment. Figure 3 shows NAMRUSA

personnel executing operational field

tests, which were conducted at Cheatham

Annex, Virginia, and Panama City, Florida,

in 2008–009.

These studies also brought the factor

of communication to light. Participants

remarked that “green is not a threatening

color,” and some thought “it could be

a signal for help.” Many felt curious about

the “blinking light” used in the study and

would go closer or try to contact the vessel

to determine the intent of the message.

Green lasers are used because they

are more visually salient; however, they

may not be as psychologically salient.

Participants remarked that if the signal

were paired with another signal, such as

an auditory one, then the message of “warning” or

“do not come closer” might be clearer.

Lastly, these studies brought to light the matter

of effectiveness. Laser glare devices are used to

stop or alter the behavior of the recipient, but one

study yielded mixed results. At close distances, participants

noticed the signal, felt affected by it, and

reported that their behavior changed in the manner

desired by the person pointing the laser. But

at greater distances, behavior might not change.

Thus, these findings need to be replicated in different

maritime scenarios in order to be truly useful in

developing laser glare devices. This particular study

Figure 3. A compact hand-held laser is evaluated for effectiveness in



maritime defense against small-boat attacks.

was encouraging regarding the effectiveness and visual

usefulness of glare devices, but it brought up

new questions about their psychological impact on

behavior. Resolving these questions must be an integral

goal of technical research and development

studies to determine the operational effectiveness of

directed-energy devices, not just for the maritime

environment, but for all military environments.

Endnote

a. Results and technical reports are available upon request from

the corresponding author or from the NAMRU-SA Public Affairs

Officer.

78

Directed Energy


High-Power Microwave



Directed Energy Using High-Power

Microwave Technology


By Jacob Walker and Matthew McQuage



The Directed Energy Warfare Office (DEWO) and Directed Energy Division at the

Naval Surface Warfare Center, Dahlgren Division (NSWCDD) merge past research

and data with continuous innovation in the field of high-power microwave(s) (HPM)

to address the critical need for nonlethal, nonkinetic weapons. HPM weapons can be

described as nonkinetic devices that radiate electromagnetic energy in the radio frequency

(RF) or microwave spectrum. They are designed to disrupt, deny, degrade,

damage, or destroy targets. In essence, this is achieved when high-power electromagnetic

waves propagate through air and interdict targets by traveling through the exterior

layers of structures and coupling energy to critical electronic components. Since

effectiveness against a wide range of targets is the goal, HPM has become a collective

term for various technologies: wave shapes, source frequencies, and the distribution of

varying signal bandwidths. It is the objective of HPM research and assessment, therefore,

to address targets for which no engagement option currently exists. NSWCDD is

working to identify optimal HPM mission platforms and move relevant technologies

into the field.


HPM Initiatives

NSWCDD has actively pursued HPM research since the advent of the field in the

1970s. Since then, scientists and engineers have conducted HPM research and development

in many areas, including hydrogen spark-gap switching, spiral generators, and

related technologies. More currently, the Directed Energy Division developed a variety

of high-power wideband RF systems based on pulsed power and Marx generators

(Figure 1). In addition to the extensive work accomplished in HPM and RF source development,

NSWCDD contributed substantially to the area of counter-HPM vulnerability

assessments. Researchers developed site assessment guides and threat brochures,

as well as a number of wideband RF sources, to determine the susceptibility of electronic

equipment to high-power RF interference. This latter effort involved assessing

and exploiting the weaknesses of specified electronic targets to various HPM and RF

threats. Data gleaned from these efforts was then used to support optimized prototypes

and system designs employing effects-based design methodology. NSWCDD utilized

these wideband RF sources to determine the susceptibility of a multitude of military


79


Directed Energy Using High-Power

Microwave Technology


Figure 1. Examples of NSWCDD Marx Generators




80

Directed Energy


High-Power Microwave



and electronic infrastructure equipment to highpower

RF interference.

HPM Counterattack

Operational Overview

Research in support of HPM-driven electronic

attack increased significantly as the demand

for nontraditional warfare emerged. Traditional

kinetic weapons often are of limited value in

peace-keeping missions, for example, as today’s

enemies frequently are embedded within civilian

populations and structures. This creates the

need for novel HPM technologies that minimize

the risk of collateral damage while effectively

neutralizing threats. Dahlgren researchers conduct

HPM system research and development—s

well as lethality and weapon effectiveness assessments—to address this need while developing

technologies against a wide variety of electronic

targets. These projects leverage NSWCDD’s assets,

including the Maginot’ Open Air Test Site

(MOATS), state-of-the-art RF diagnostics, and

modeling and simulation tools to identify applications

and platforms in which HPM technologies

can be employed. Figure 2 shows a computer

model of the MOATS facility and a modeling and

Figure 2. Modeling and Simulation Depicting (a) NSWCDD Test Facility and (b) Simulation of Radiated RF



(a)

(b)

81


Directed Energy Using High-Power

Microwave Technology


simulation graphic depicting the RF emitted by

an HPM dipole antenna.

Potential platforms for HPM integration include:

man-portable, aerial, vehicle, and vesselmounted

systems. These platforms all provide

unique methods for delivery of HPM sources. For

example, aerial delivery—which, in many ways, is

the most challenging due to size and weight constraints—

can increase the effective range of these

systems and can engage multiple targets at close

range without endangering personnel. Likewise,

vehicles and vessel-mounted HPM systems provide

a way for law enforcement and the military to

stop vehicles in chase scenarios almost as soon as

they begin. The goal of all of these projects is to

provide military forces with the ability to employ

nonkinetic, electronic strike technologies against

an adversary’s electronics.

The DEWO and Directed Energy Division are

uniquely positioned to provide numerous capabilities

for in-house development while engaging

with the private sector to test and provide feedback

on HPM systems developed externally. In

the past decade, NSWCDD has evaluated several

HPM systems at Dahlgren to determine their effectiveness

against various electronic targets while

maintaining the Office of the Secretary of Defense’s

Tri-Service RF Directed Energy Weapon (DEW)

Database. This database contains all effects data

collected from directed-energy tests performed

within the U.S. Air Force, Army, and Navy.

Conclusion

NSWCDD continues to pioneer HPM source

development and lethality and integration studies,

leading to the demonstration and delivery of

prototype capabilities. It also is committed to researching

and developing critical subsystems for

HPM delivery. By leveraging numerous target assets

and sophisticated diagnostic equipment—in

conjunction with MOATS—NSWCDD has positioned

itself at the forefront of HPM electronic

attack, leading the way in the development and delivery

of these capabilities to the warfighter.

Acknowledgment

Nancy Muncie, Bowhead, contributed to this

article.

82

Directed Energy


High-Energy Laser



Laser Counter Rocket, Artillery,

and Mortar (C-RAM) Efforts


By Michael Libeau



Mortars and rockets are common weapons confronting U.S. troops abroad. Insurgents

fire the inexpensive projectiles into populated areas, intending to kill or injure

service members and to inflict physical damage. While kinetic solutions like guns and

missile interceptors are used to counter rockets and mortars, laser counter rocket, artillery,

and mortar (C-RAM) systems present a promising solution to counter these challenging

threats in the near future.

Scientists and engineers at the Naval Surface Warfare Center, Dahlgren Division

(NSWCDD) have been researching, developing, testing, and evaluating laser C-RAM

systems through collaboration, modeling and simulation, and experimentation. The

Joint Technology Office (JTO) and the Directed Energy and Electric Weapons Program

Office (PMS 405) sponsored the first year of these initiatives in 2007. Consecutive and

current work has been sponsored by the Office of Naval Research (ONR) Expeditionary

Maneuver Warfare and Combating Terrorism S&T Department.

Background

In preparation for the development of a laser C-RAM system, an understanding

of the vulnerability of rockets and mortars to laser energy was crucial. Engineers from

NSWCDD and the U.S. Army Space and Missile Defense Command (SMDC) collaborated

on laser C-RAM efforts. Engineers analyzed the RAM threat and examined a

variety of targets, accessing RAM vulnerabilities to laser energy by utilizing theoretical,

numerical, and experimental work. They then developed theoretical models that

captured the physics of the laser-induced failures of targets containing high explosives

(HE). Additionally, NSWCDD engineers enhanced lethality simulations using a tool

called the Effectiveness Toolbox to model engagements of RAM targets with laser energy.

Figure 1 shows a screen capture from the Effectiveness Toolbox.

The resulting simulations included results from a laser atmospheric propagation

model and a thermal model to determine the effect of the laser energy on the target. The

simulations also incorporated target trajectories necessary for modeling the changing

laser conditions on the target resulting from the engagement of a ballistic target. Subsequent

to modeling these effects, live testing was performed. Figure 2 shows the lasing

and destruction of a RAM target during live testing.

83


Laser Counter Rocket, Artillery,

and Mortar (C-RAM) Efforts


Figure 2. Explosive Target is Destroyed with NSWCDD’s Fiber Lasers

Figure 1. Screen Capture from the Effectiveness Toolbox Showing the Laser Engagement of a Mortar Target




84

Directed Energy


High-Energy Laser



Figure 3. Laser Power Spatial Variation from a C-RAM Test




NSWCDD engineers conducted two large experimental

tests to determine the vulnerability of

HE targets to laser energy using NSWCDD’s High-

Energy Fiber lasers. The first test was conducted

jointly with SMDC. During these two tests, over

40 RAM targets were destroyed under different laser

conditions, producing significant information

on laser lethality. Researchers measured the failure

times of multiple targets for different laser powers,

spot sizes, incidence angles, and aimpoints. The experimental

data yielded by the tests increased engineers’

understanding of the vulnerability of targets

containing energetic materials. This data was then

used to benchmark predictive models.

Future tests are planned with additional HE

targets to further the knowledge of RAM vulnerability.

These tests are controlled and conducted

carefully to ensure that good data is obtained. Accurate

measurements of laser power on the target

and the resulting target failure times must be made

during the tests. To that end, NSWCDD engineers

leverage Division-wide expertise in lasers and optics

with its long history of explosives testing to

achieve meaningful test results. NSWCDD personnel

have been instrumental in improving techniques

to measure the spatial profile of laser power

on a target. The spatial distribution of laser power

on a target is critical to understanding the target’s

failure. Figure 3 shows a laser beam’s spatial power

distribution measured during a test.


Ongoing Laser C-RAM Initiatives

Recent advances in fiber lasers have increased

the power outputs of these rugged, solid-state devices.

Both government and contractor efforts are

examining the application of commercial off-theshelf

(COTS) lasers and other electric lasers for

application into advanced weapon systems. The

Navy’s Laser Weapon System (LaWS) Program, for

example, is examining a laser system built around

efficient fiber lasers. This is significant because a

high-energy fiber laser system offers two critical

advantages over gun and missile interceptor CRAM

systems. First, the laser has a great depth of

magazine since it requires only electricity for operation.

Consequently, unlike a gun system, which

has a limited supply of ammunition, a laser system

is limited only by its supply of electrical energy.

Second, a laser system offers a cost per kill

that is significantly lower than alternative systems

because only electricity is being expended instead

of gun ammunition or a costly missile interceptor.

This low cost per kill also better matches the low

cost of the RAM target being engaged.

High-Energy Fiber Laser C-RAM systems will

provide significant advantages in defeating the

RAM threat while augmenting existing C-RAM

solutions. More importantly, laser C-RAM systems

will help protect members of the armed forces

from the inexpensive, yet often deadly threats

posed by rockets and mortars.


85


Laser Counter Rocket, Artillery,

and Mortar (C-RAM) Efforts


86


Directed Energy


Nonlethal Capabilities



Multifrequency Radio-Frequency (RF)

Vehicle Stopper


By Stephen A. Merryman



The widespread use of vehicle-borne improvised explosive devices (VBIEDs) in Iraq

and Afghanistan has resulted in large numbers of military and civilian personnel being

killed or injured. Consequently, the Joint Non-Lethal Weapons Directorate’s (JNLWD)

top priority is to identify, investigate, and develop technologies and capabilities to nonlethally

stop both vehicles and vessels outside of minimum “keep-out ranges” (i.e., ranges

where the rules of engagement would dictate the use of lethal force) and to mitigate

the blast effects from a VBIED.

One of these technologies is the multifrequency Radio-Frequency (RF) Vehicle

Stopper (RFVS), a high-power microwave (HPM) weapon under development at the

Naval Surface Warfare Center, Dahlgren Division (NSWCDD). A prototype RFVS system,

designed to meet the mission criteria for fixed-checkpoint protection and compound

protection, is slated for completion in FY13. Science and technology (S&T) work

continues in parallel to the prototype system’s construction to broaden its applicability

to include convoy protection and the establishment of a quick safe zone. This article describes

the 4-year research effort that resulted in the specification of the RFVS system

design. Figure 1 shows an illustration of a candidate RFVS platform with the system set

up for fixed-checkpoint protection.

The RFVS system uses high-power magnetron tubes to generate intense RF pulses

that interfere with a vehicle’s electronics, rendering it temporarily inoperable. The engine

cannot be restarted while the RF is on but is readily restarted once the RF is turned

off. Thus, the RFVS system allows for the maintenance of a safe keep-out zone in situations

that might otherwise require the use of lethal force. The defined measure of success

for this system is a demonstrated, effective capability against more than 80% of the candidate

target-vehicle-class list, which includes passenger cars and large vehicles.

As a nonlethal capability, the effects to the target vehicle are short term and almost

always reversible, so that the vehicle is not stranded, which would burden the warfighter

with the task of its removal. Moreover, as with all directed-energy weapons, the RFVS

system delivers energy at the speed of light. In contrast with other nonlethal vehicle

stopping concepts and systems, however, RFVS does not need to be pre-emplaced and

has a limitless magazine.

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Multifrequency Radio-Frequency (RF)

Vehicle Stopper


Background

Using HPM or RF energy to stop an automobile

engine is not a new concept; it has been under

investigation for some time in private, academic,

and military sectors. To that end, the RFVS program

leveraged as much historic work as possible

while collaborating with academic and military

laboratories and while aggressively pursuing contacts

in the automobile industry to gain knowledge

of vehicle electronic design and function.

In 2005, the JNLWD funded the then-Directed

Energy Technology Office (DETO) at NSWCDD

to perform an extensive reverberation chamber

test series to characterize the vulnerability of a representative

cross section of automobiles to a wide

range of HPM source frequencies.a The purposes



of the tests were twofold. First, the applicability

of the Army’s Ground Vehicle Stopper (GVS)

data set needed to be established for newer vehicles,

and second, a thorough, source-technology

independent assessment of vehicle vulnerabilities

needed to be performed. The rationale behind the

latter was to establish vehicle vulnerabilities without

inadvertently biasing the process. Only after

the full assessment was performed would factors

such as concept of operations (CONOPS) and system

requirements come into play. Figure 2 is a photograph

of reverberation chamber testing.

Over the past decade, a significant number of

private, academic, and military laboratories have

investigated the susceptibility of automobiles to

HPM energy. The range in approaches spans the

gamut from isolated component testing, through

direct injection and radiated testing of electronic

control units (ECUs), and continuing through full

vehicle radiated testing. Each of the different test

methods has its strengths and weaknesses. Testing

of isolated ECUs in controlled laboratory conditions

is arguably the best way to determine exactly

how a specific unit is responding to the RF. However,

whether or not the identified susceptibilities

continue to hold true when the unit is in place in a

Figure 1. Illustration of Candidate RFVS System Setup for Checkpoint Protection




88

Directed Energy


Nonlethal Capabilities



vehicle, or whether the results apply to other vehicles’

ECUs, remains a significant question that limits

the applicability of the results.

Full vehicle testing and failure analysis of the

ECU can be a daunting task. That said, full vehicle

testing affords the advantage of ensuring that

the response is commensurate with expectations

of genuine engagements. The test approach one

chooses to take depends upon resources, test facility

availability, and most importantly, the objectives

of the program. For the RFVS program, the objectives

were to identify an HPM waveform that is

effective against a broad class of the candidate target

vehicles and to ensure that the identified waveform

could be generated with a source that can be

packaged in a footprint and cost amenable to military

users. To meet the program’s objectives, the

RFVS program chose to invest the majority of its

resources in full vehicle testing. While the focus of

the effects testing portion of the RFVS program has

remained on full vehicle testing, both time and resources

have been devoted to fostering and maintaining

connections with academia and the auto

industry. There is concerted effort to keep abreast

of the latest trends in automotive technology, to

ensure that the current RFVS system design will

continue to be effective against future vehicle designs,

and to leverage all research that might aid in

future RFVS designs.

System Operation

The majority of current HPM system concepts

employ a narrowband, single-frequency HPM

source. In contrast, RFVS utilizes multiple HPM

Figure 2. Vehicle on a Dynamometer in the NSWCDD Reverberation Chamber




89


Multifrequency Radio-Frequency (RF)

Vehicle Stopper


frequencies. The rationale for using multiple frequencies

is associated with increased system effectiveness.

Electromagnetic (EM) energy can be used

to disrupt or damage an electronic target. In order

for the energy to affect the electronics, however, it

must be able to reach a critical component(s) inside

the target. This involves a process referred to

as coupling. Different EM waveforms are more or

less effective against specific targets depending, in

part, on their frequency, as different frequencies

couple better or worse depending on varying target

geometries. To be specific, each piece of electronics

has specific resonance frequencies that most effectively

facilitate coupling energy to the target.

Unfortunately, these resonant frequencies can be

unique to each piece of equipment. Consequently,

a single-frequency waveform might be very effective

against one target, but less effective against another

target. Therefore, a system that utilizes either

a sweep of frequencies or multiple frequencies will

be more effective against a larger target set. This is

not a novel idea, but rather one that has been readily

acknowledged within the HPM community for

some time and fervently embraced by the RFVS

program. Current technology limitations prohibit

high-power-swept frequency sources as viable

options, leading to the idea of a multifrequency

source. The more frequencies that are used, the

more effective the system; however, a trade-off is

made with system size and cost as the number of

source frequencies is increased.

Brassboard System

After completion of the exhaustive vehicle effects

characterization testing in 2006, the RFVS

program identified the optimal number of frequencies

needed to meet mission requirements. It

then used this information in the design and construction

of the Brassboard System. The purpose in

constructing the Brassboard System was to demonstrate

the benefit of the multifrequency approach

and the ability to meet mission objectives with

specified power on target requirements. Construction

of the RFVS Brassboard System began in 2007

and was completed in 2008. The Brassboard System

was not constructed with specific system footprints

in mind. Thus, the antenna and conex used

are significantly larger than those in the prototype

design. The RFVS team collaborated with a Marine

Corps service representative identified by the

JNLWD to flesh out the specifics of the mock

checkpoint to be used in the RFVS Brassboard System

Demonstration. Figure 3 provides a diagram

of the checkpoint setup used in the RFVS Brassboard

Demonstration. Figure 4 provides photographs

of the RFVS Brassboard System.

Figure 3. Schematic of Checkpoint Setup




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Directed Energy


Nonlethal Capabilities



Figure 4. Photograph of the RFVS Brassboard System and Demonstration Setup



Demonstration Test Setup

91


Multifrequency Radio-Frequency (RF)

Vehicle Stopper


The Brassboard System Demonstration was

conducted in Spring 2008. The Demonstration

was a success, and funding for the RFVS prototype

was consequently approved. To date, 42 passenger

vehicles (cars, pickup trucks, vans, and sport

utility vehicles (SUVs)) and 3 large trucks (dump

truck and tractors) have been tested as part of the

RFVS program.

Way Ahead

The JNLWD continues to work with the Directed

Energy Warfare Office (DEWO) toward the

development of a fieldable multifrequency RFVS

system. Once the capability is fully developed,

tested, and certified ready for operational use,

warfighters and civilians alike will benefit greatly.

Lives will no doubt be saved using the ability to

stop vehicles nonlethally and mitigate the blast effects

from VBIEDs.

Acknowledgment

Dr. Cynthia Ropiak (SAQ Consulting) contributed

to this article.

Endnote

a. The Directed Energy Technology Office (DETO) was renamed the

Directed Energy Warfare Office (DEWO) in August 2009. For reference,

see the charter for the DEWO, NSWCDD, 17 August 2009.

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Directed Energy


Nonlethal Capabilities



High-Power Electrical Vehicle-Stopping Systems


By Jordan Chaparro and Melanie Everton



The military needs devices that can safely and reliably stop or arrest vehicles. The

primary concern is security at entry control points and vehicle check points similar to

the one shown in Figure 1. In such scenarios, it is desirable to be able to stop unauthorized

vehicles at predefined standoff ranges to protect personnel, equipment, and critical

infrastructure.

Both the military and civilian law enforcement agencies face similar issues with

chase scenarios, where concerns over bringing an offending vehicle to a stop without

killing or injuring innocent civilians, or causing collateral damage, often prolongs highspeed

pursuits. That said, currently employed nonlethal options for arresting vehicles

have significant logistical limitations and carry a high cost per use.

The Naval Surface Warfare Center, Dahlgren Division’s Directed Energy Warfare

Office (DEWO), under the sponsorship of the Joint Non-Lethal Weapons Directorate

(JNLWD), investigated compact systems designed to couple high-power electrical impulses

to a target vehicle to stop its engine. Such systems are highly portable, can operate

remotely, can be deployed quickly by a two-man team, and can engage hundreds of

targets before requiring any significant maintenance.

System Overview

Conceptually, electrical vehicle-stopping systems are fairly simple devices. The systems

use several stages of energy compression to take a low-peak power source—like a

battery pack—and create very intense, short-duration, oscillating electrical impulses. The

block diagram, shown in Figure 2, illustrates the principal components of such a system.

A high-energy density, 300-V lithium battery pack, similar to what might be found

in a hybrid vehicle, serves as the prime power source for the device. These batteries are

capable of driving the system for hundreds of engagements before requiring recharge.

The direct current bus from the batteries is stepped up to several kilovolts in order

to charge a capacitive voltage multiplier, such as a Marx Generator, Spiral Line Generator,

or Tesla Transformer. Once triggered, these generators charge a resonant circuit to

hundreds of kilovolts which, when switched, generate the desired oscillating waveform.

Coupling this electrical pulse to a target may be accomplished by direct electrode contact,

by radiating the waveform from a broadband antenna structure, or by a combination

of both methods.

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High-Power Electrical Vehicle-Stopping Systems


Figure 1. An Azerbaijani Soldier Guarding Entry Control Point 1 at the Haditha Dam in Support of Operation Iraqi Freedom

Figure 2. System Block Diagram for Generic Electrical Vehicle-Stopping Systems




94

Directed Energy


Nonlethal Capabilities



The system is monitored and controlled by

an integrated system computer. A laptop computer,

remotely connected to the system controller

through either fiber optic or a wireless network,

can be used to arm the system. At this point, motion

detection sensors trigger the pulse train upon

the targeted vehicle. The laptop can also be used to

monitor the system’s status, change system parameters,

and receive data collected during the last engagement

event.

A conceptual rendering of how such a system

might look when in use is shown in Figure 3.

Traffic would be funneled with barriers to a single

lane. When not engaged, the system electrodes

would sit flush with the roadway unit, with an exposed

height of less than 3 inches. When required,

the electrodes could be released to make contact

with a vehicle’s undercarriage and deliver the electrical

impulses.

Comparison with Existing Systems

Tire spike systems are frequently employed but

do not limit the momentum, drive, or control of a

vehicle to an extent that could be useful in any type

of control or checkpoint scenario. Consequently,

while tire spike systems are primarily used in highspeed

pursuit applications, they are limited, in that

they cripple the target just enough to allow law enforcement

to force the vehicle to a stop.

Restraining nets are most comparable to electrical

vehicle stoppers with respect to their intended

application and desired effect. Restraining net

systems and electrical vehicle stoppers both completely

arrest vehicles, although by different means.

Restraining nets bind the front axle of the vehicle,

causing it to forcibly lose momentum and skid to

a stop. Thus, the vehicle operator loses the ability

to steer the vehicle, further resulting in a lower

potential for collateral damage. Electrical systems

stop the engine of the vehicle, leaving the operator

with control for the duration of the vehicle’s momentum.

Physical barrier structures can then be

employed to force an affected vehicle to stop in a

fairly short distance. Modern vehicles lose power

steering when the engine is cut off, such that the

maneuverability of the vehicle is limited enough to

Figure 3. Conceptual Rendering of an Employed Electric Vehicle Stopping System




95


High-Power Electrical Vehicle-Stopping Systems


allow normally nonrestrictive serpentines to be effective

at limiting roll-off distances.

One key logistical advantage of electrical vehicle

stoppers, compared to restraining nets, is the

average cost per engagement. Restraining net systems

are one-time use devices that cost several

thousand dollars each. Electrical systems initially

cost tens of thousands of dollars but can perform

thousands of stops within the expected lifetime of

the device. Also, there is no requirement to physically

reset or reload an electrical system, as with

restraining nets. The maintenance required for

electrical systems involves the occasional replacement

of electrode arms and the inspection of the

system connections and pressure levels.

Operationally, both systems have limitations on

the types of targets that can be effectively stopped.

Restraining nets are limited by vehicle momentum,

which can be a product of high speeds or large

vehicles. Electrical systems are not limited by vehicle

size or speed, but they require additional support

from structures—such as serpentines or speed

bumps—to force the target to brake and dissipate

its momentum once the engine has been stopped.

Both devices typically cause damage to targeted,

stopped vehicles. Restraining nets almost always

cause tire damage. Less commonly, brake

lines, front axles, wheels, and transmissions also

might be damaged. Electrical systems typically

damage engine controllers, security modules, and

engine sensors. In addition, noncritical parts—

such as gauges, radios, and cabin fans—also might

be damaged. Moreover, moving affected targets is

much less of an issue with electrical stoppers than

vehicles stopped by net systems, which must first

have the net cut away and freed before the target is

moved to the side of the roadway.

System Refinement and

Look Forward

Previous attempts to field electrical vehiclestopping

systems have been hampered by limited

success rates on a large population of vehicles.

Many models of vehicles are easily affected by any

type of large injected current, while others are fairly

resistant. Through carefully designed and controlled

experiments, and logistical regression

modeling techniques, the DEWO team has been

able to determine key waveform attributes that

scale with stopping effectiveness rates on a representative

population of vehicles. Successful stop

rates exceeding 90 percent have been achieved on

a diverse vehicle test set by engineering system

resonators to enhance system performance The

DEWO team, through continued research, testing,

and evaluation, is continuing its work to increase

the reliability and effectiveness of these systems to

make them more compact and to improve their

functionality for future military and law enforcement

applications.

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Directed Energy


Nonlethal Capabilities



Nonlethal Small-Vessel Stopping With

High-Power Microwave Technology


By Jacob Walker

97


Nonlethal Small-Vessel Stopping With

High-Power Microwave Technology


Figure 1. Depiction of a Small-Vessel Swarm Ready to Attack



The employment of small vessels to attack merchant

ships and other seafaring units has emerged

as a significant threat to international navigation

and safe operations on the high seas. Along with

swarm tactics, small vessels have been known to

carry improvised explosive devices, help smuggle

terrorists and weapons, and serve as attack

platforms on the water for larger weapons. While

kinetic solutions serve as the decisive option, alternative

solutions that employ nonlethal means are

being explored. A depiction of a swarm of small

vessels ready to attack is shown in Figure 1.

The Naval Surface Warfare Center, Dahlgren

Division’s (NSWCDD’s) Directed Energy Warfare

Office (DEWO) is evaluating directed-energy (DE)

concepts based on high-power microwave (HPM)

technology for nonlethal vessel-stopping applications.

Nonlethal weapons are defined by the Department

of Defense (DoD) as weapons that are

explicitly designed and primarily employed so as to

incapacitate personnel or materiel while minimizing

fatalities, permanent injury to personnel, and undesired

damage to property and the environment.1



Several methodologies exist for using nonlethal

means to stop small vessels. They include:

Running-gear or prop entanglement systems

Exhaust stack blockers

A sea-anchor vessel-stopping system, which



casts a net across the bow of a vessel to impart

resistance

Small-craft disablers, which insert a spear



into the hull and deploy a fin that drags in

the water, making steering impossible

Prop entanglement systems, exhaust stack

blockers, and sea-anchor systems are useful and effective,

but all are operationally difficult to deliver

when deployment methods rely on positioning

them in front of, or directly over, a vessel moving

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Directed Energy


Nonlethal Capabilities



at high speeds. Small-craft disablers also are a formidable

vessel-stopping solution and may be easier

to deploy, but they cause permanent damage to

the vessel in question.

Under the direction of the Joint Non-Lethal

Weapons Directorate (JNLWD), the DEWO is in

the initial stages of a multiyear effort to evaluate

DE concepts for nonlethal vessel-stopping applications.

It is currently focusing on HPM technology.

This technology uses HPM sources to radiate radio

frequency (RF) pulses downrange to interfere with

motor-control electronics and significantly impede

or stop small-vessel motors with minimal collateral

damage. These RF pulses can be generated using

different technologies ranging from wideband LC

oscillators and microwave tubes (e.g., magnetrons,

klystrons, and backward wave oscillators) to emerging

solid-state technologies (e.g., nonlinear transmission

line and photo-conductive switching). An

outboard motor on a test stand is shown in Figure 2.

In comparison to kinetic weapons or other nonlethal

systems, HPM avoids gross physical destruction

to the vessel while, more importantly, providing

zero-to-low risk of human injury. HPM accomplishes

this at safe distances using speed of light delivery,

therefore making evasion difficult, if not impossible,

with the added benefit of scalable effects ranging

from disruption to damage. Despite its numerous

advantages, the use of HPM technology as a nonlethal

weapon presents challenges as well, including

a trade-off between system size and standoff range.

This is particularly important when considering the

use of HPM systems in different environments.

Upfront HPM source development costs represent

one of the biggest challenges. However,

long-term savings associated with HPM technology

can offset this challenge. For example, prop entanglement

systems might be deployed only once

before they are rendered useless. HPM sources

integrated onto a ship or other military vehicle

can be employed in potentially thousands of missions,

therefore resulting in a lower cost per single

use, bringing overall associated costs of the system

down significantly. Priorities for HPM nonlethal

weapons include developing a system effective

against different types of small vessels.

NSWCDD’s Directed Energy Division began

HPM susceptibility testing to determine the effectiveness

of HPM weapons against relevant outboard

engines. This involves testing small vessels in

Figure 2. Outboard Motor Test Stand




99


Nonlethal Small-Vessel Stopping With

High-Power Microwave Technology


a variety of environments, including reverberation

and anechoic chambers, and open-air testing. All

help identify different, effective waveform parameters

such as frequency, pulse width, rise time, and

required power or energy on target. They further

facilitate the identification of design specifications

necessary for an eventual HPM source. This source,

once developed, will then be integrated into one

of several potential platforms. Candidate concepts

of deployment include U.S. Coast Guard and naval

vessels in addition to unmanned surface or aerial

vessels. Another potential application might be

to supplement existing Coast Guard or Navy platforms

used for fast-boat interdiction with an HPM

vessel-stopping capability. A small-vessel test using

an HPM source is shown in Figure 3.

Developing solutions for the growing threat

that small vessels pose to navigation and safe operations

in the world’s oceans is one of JNLWD’s

top priorities. Using nonlethal HPM weapons to

stop vessels will provide the warfighter with a viable

option for swarm threat and fast-boat interdiction.

DEWO is working diligently to accelerate this

technology and provide a DE alternative to kinetic

weapons and fulfill this long overdue capability gap.

Figure 3. Small-Vessel Testing Using a High-Power Microwave Source



Reference

1. Department of Defense Dictionary of Military and Associated

Terms, Joint Publication 1-02, 12 April 2001 (as amended through



19 August 2009).

Directed Energy


Volume 7, Issue No. 4


We look forward as we provide enterprise-wide

technical and strategic leadership for the efficient

and effective development, acquisition, and fielding

of directed-energy systems for the warfighter.



Dale Sisson


Head, Electromagnetic and

Sensor Systems Department

NSWCDD, Dahlgren, Virginia


NSWCDD/MP-09/34


Statement A: Approved for public release; distribution is unlimited


Fallen Warriors


Here we honor those who died while serving their country


Volume 7, Issue No. 4

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