By Lt. Col. Siegfried Ullrich

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Directed Energy Technology: Transforming the Future of Warfare

Military use of directed-energy technology has moved beyond the realm of science fiction. In the past two decades, directed-energy technologies have quickly matured from the research laboratory, to the operational force, and have become highly effective instruments of war. Directed-energy technologies currently enable and enhance a multitude of today’s weapons, weapons platforms, targeting devices, mapping applications, and communications systems.[1] Recent developments in directed-energy technology show immense potential for future military systems. Moreover, new threats posed on today’s battlefield suggest that directed-energy will rapidly become the military’s most consequential and transformative technology. The following article defines directed-energy types, discusses their various military uses, and gives a way ahead for future development.

What is Directed-Energy?

The U.S. Department of Defense (DoD) describes directed-energy as an umbrella term, covering technologies that produce a beam of concentrated electromagnetic energy, or atomic or subatomic particles.[2] Directed-energy uses various wavelengths of the electromagnetic spectrum, travels at the speed of light, and the effects of gravity do not impede it. These qualities can deliver precise targeting, instant effects, and provide the possibility of extremely long range. Consequently, these advantages provide the means to support a wide spectrum of military equipment and capabilities.[3]

Recently, many developing technologies have seen a significant decrease in size; this trend includes directed-energy systems. Early models were typically large, awkward, and required immense amounts of energy; therefore, were impractical for placement on a weapons platform. Today’s directed-energy technology can fit in small containers, allowing for incorporation in satellites, UAS payloads, perimeter security systems, aircraft, and ground vehicles.[4] Consequently, directed-energy technologies are currently in military use as laser range finders, target designators, Directed-Energy Weapons (DEWs), laser remote sensors, and laser communications systems.

Laser Range Finders and Target Designators

Laser range finders and target designators are a common type of directed-energy technology on today’s battlefield. For nearly fifty years, militaries have used lasers to assist traditional (i.e. chemically-powered) weapons with target engagement. Lasers improve targeting by reducing the timelines between identification, tracking, and shooting. Combined, laser range finders and target designators accurately mark targets by illuminating them with a tightly fixed beam of light. Once illuminated, the host platform or weapons system captures the light reflected from the target. The weapons systems, or platform, can then track the signal and provide the target’s distance and speed data to the host weapon platform or weapon aiming system. In addition, laser range finders and target designators can provide three-dimensional vision control, positioning control, and level control for weapon and platform guidance systems.[5] Furthermore, laser range finders assist with determining distance between friendly and adversary satellites in the space domain.

Despite their current success, laser range finders and target designators have limitations. Lasers require a clear line of site to properly illuminate the target. Therefore, topography, foliage, structures, and thick smoke can prevent illumination. If a laser beam fails to reflect back to its host sensor, it will be unable to find, fix, and track its target. Militaries have already begun working on reflective and absorptive vehicle coatings that can prevent laser effectiveness.[6] Although these factors limit the use of laser range finders and target designators, future technology may find ways to mitigate these issues.

Directed-Energy Weapons (DEWs)

The U.S. DoD defines a DEW as “a system using directed-energy, primarily as a direct means to damage or destroy enemy equipment, facilities, and personnel.”[7] Its ability to concentrate and manipulate the electromagnetic spectrum make directed-energy technology an effective weapon. Conventional munitions, such as rockets, bullets, and artillery rounds destroy targets through the transfer of kinetic energy. In contrast, DEWs use electromagnetic energy to produce the same destructive effect.[8]

Evidence shows that DEWs will soon replace traditional (i.e. chemical-powered) weapons on the battlefield.[9] In the future, DEWs will provide a number of capabilities and advantages over traditional weapons. When paired with complex sensors, DEWs can track, aim, and fire with pinpoint accuracy. In addition, they have few moving parts and a virtually unlimited magazine capacity, which allows for lower operating and maintenance costs. Furthermore, DEWs are silent, offer plausible deniability, can travel immense distances, and engage multiple targets. Moreover, an operator’s ability to adjust power and frequency of DEWs allows a wide range of scalable options. This scalability allows DEWs to generate non-lethal effects to equipment, such as sensor blinding and burning circuitry.[10]

Laser Weapons

Laser weapons are beams of focused light that cause damage to a target by creating heat.[11] The power level produced and the operational mission performed determines a laser weapon’s classification. The laser’s specific wattage level categorizes it as either low-energy, medium-energy, or high-energy. Low-energy laser weapons can jam sensors in communications systems, blind the eyes of an adversary, or simulate weapons during training events. Medium-energy laser weapons can blind and damage optical or optoelectronic devices on the ground, in the air, or in space. High-energy laser weapons can physically destroy electronic components within aircraft, missiles, and satellites.[12]

Several militaries regularly use low-energy lasers for a variety of missions. The most common military use is in training devices; an example of which is the Multiple Integrated Laser Engagement System (MILES). MILES enhances military training by using blank ammunition and low power lasers to simulate a variety of weapons systems. It uses sensors attached to soldiers and equipment, to collect laser fire that mimics the effective range of actual ammunition.[13] Another commonly used low-energy laser is the dazzler. Dazzlers use laser light to temporarily blind sensors, optics, and personnel.[14] Dazzling is especially effective because it can perform as a non-lethal and non-permanent weapon against various ground, sea, and airborne targets. In addition, low-energy lasers can detect communications jammers, human activity, and munitions.[15]

Today’s medium-energy lasers have the ability to damage a wide variety of sensors and circuitry. Most contemporary weapons platforms use various optical or optoelectronic sensors to assist with finding, fixing, and destroying an adversary’s capabilities. In recent tests, medium-energy laser weapons have been effective at inflicting physical damage to optical and optoelectronic devices in the war-fighting domains of land, sea, and air. Medium-energy lasers can also be used to permanently blind personnel over a large area. Lasers can permanently blind an entire unit, without warning, and in less than two-millionths of a second. Moreover, it has the power to enter the human eye obliquely. Therefore, it does not have to directly target the eye to cause blindness. [16] The ability to permanently blind numerous advisories over a wide area makes this a highly effective, but controversial weapon. Medium-energy lasers have already proved effective during testing, and will soon be operational on the battlefield.

Recently, there has been a renewed interest in high-energy lasers, resulting in subsequent advances in their technology. A number of new threats, such as Improvised Explosive Devices (IED), UAS swarms, small boat swarms, and the proliferation of rockets and missiles, have spurred laser-energy technology developments.[17] The recent introduction of numerous weapons platforms, traveling at high-speed and located in multiple domains, has created a significant challenge to the modern warfighter. Contemporary chemically powered weapons lack the ability to counter these new and complex threats. When compared to laser weapons, contemporary chemically powered weapons are heavy, have a slow rate of fire, have limited ammunition, are expensive, and their destructive power is difficult to adjust. In order to close the capability gap, militaries must have defenses that can engage multiple, high-speed, and maneuverable targets. A laser with an uninterrupted power source has a limitless amount of ammunition. Therefore, it can engage multiple targets, multiple times. In addition, lasers provide the option to strike from beyond visual range, at the speed of light, with precision and instantaneous effects. Moreover, the cost per shot of a laser is significantly lower than that of conventional weapons. The U.S. Navy’s Office of Naval Research has suggested that a typical 110kW high-energy laser, for a multi-second shot would cost less than a dollar per round.[18] In addition, the logistical footprint of lasers is far less than conventional weapons, when considering the weight, bulk, and hazards of storing and transporting chemically powered munitions.

Improvements and further advancements of high-energy lasers provide for unlimited possibilities. High-energy lasers that can intercept ground vehicles, ships, aircraft, missiles, and satellites already exist. Currently, several militaries across the globe are testing these weapons. One of several U.S. laser weapons presently in development is the U.S. Army Space and Missile Defense Command’s (USASMDC) Mobile Experimental High Energy Laser (MEHEL). The MEHEL is a 5kW laser weapon, mounted on a Stryker armored fighting vehicle. Recently the MEHEL participated in, and won, the Joint Improvised-Threat Defeat Organization’s (JIDO) UAS Hard-Kill Challenge. The purpose of the Hard-Kill Challenge was to assess technologies that would be most proficient at intercepting enemy UAS systems. In addition, the Hard-Kill Challenge informed senior decision-makers on the current state of various technologies, and how they can best deal with single and multiple UAS targets.[19] The MEHEL’s recent success at the Hard-Kill Challenge serves as an example of how high-power laser weapons can be effective against present and emerging threats.

Assaults from swarms of small ships, swarms of UASs, and missiles, will be prevalent in future conflicts. Naval vessels will be especially vulnerable to these types of attack, due to their large size, slower speeds, and large electronic footprint. Recognizing this vulnerability, the U.S. Navy developed, installed, and deployed the AN/SEQ-3 Laser Weapons System (XN-1 LaWS) on the USS Ponce. The XN-1 LaWS is specifically designed for use against low-end asymmetric threats, such as small boats and UASs. One of the most important aspects of the XN-1 LaWS is its capability for scalable actions. It can temporarily blind personnel, and burn through electronics on aircraft, ship engines, on-board ship munitions, and inflight UASs. Currently, the commander of the USS Ponce has authorization to use the system as a defensive weapon during its operations in the Persian Gulf. The XN-1 LaWS has demonstrated the capability to be effective against modern weapons systems located in the sea and air domains.[20]

High-energy lasers have demonstrated some of their greatest potential in the space domain. Civilian infrastructure and military systems are increasingly reliant on space-provided capabilities. Recognizing this reliance, potential adversaries are quickly developing ways to disrupt the use of the space domain. In recent years, high-energy laser weapons have revealed increased capabilities in space. In 2006, the director of the U.S. National Reconnaissance Office (NRO) confirmed that a ground-based laser, operating in China, had illuminated one of its spy satellites.[21] Recently, numerous civilian and military earth-observation satellite owners have reported temporary blinding caused by laser dazzlers. [22] Although these attacks did not produce permanent damage, they demonstrate that lasers have the ability to target satellites, and with additional power could be capable of destroying sensors and critical circuitry.

The military relies on space for numerous military systems and operations, and lasers provide effective space weapons. A satellite in Low Earth Orbit travels at nearly 17,500 miles per hour, and is 150 to 1500 miles above the earth’s surface. A satellite’s hyper-speed and high altitude make it a challenging target. Therefore, high-energy laser weapons are an obvious choice for use against an adversary’s satellites, due to their long range, accuracy, and ability to create effects at the speed of light. In addition, gravity and wind conditions have minimal effect on laser weapons. This is especially helpful with accuracy when shooting hundreds of miles from the earth’s surface into the zero gravity domain of space. Furthermore, a laser weapon’s potential to engage a target multiple times in a matter of seconds, significantly increases the likelihood of hitting a target. These factors demonstrate that a laser’s capability to operate in the space environment makes it an ideal anti-satellite weapon.

Although DEWs possess advantages to the current and future forces, they also have limitations. Distance and weather conditions provide severe restrictions for laser weapons. Particulates in the air, such as smoke, dust, and water molecules, scatter and absorb laser light, resulting in power loss. An infrared laser will lose half its potency after traveling 2.5 miles on a clear day and less than a mile on a humid day.[23] The heat generated by lasers provides another drawback. In the process of delivering heat to a target, lasers also generate heat within their own operating system. Therefore, DEWs require a cooling system to prevent overheating between shots. Consequently, cooling systems add an enormous amount of bulk that can burden ground and air weapons platforms.[24] Laser cooling systems have significantly decreased in size over the past 30 years. However, it may take substantial time to reduce a high-energy laser’s cooling system to an adequate operational size. Another limitation is that laser beams can only travel in straight lines. Consequently, they can only hit targets in direct line-of-site, or above the horizon. In the future, relay mirrors on UASs or satellites may solve the direct line-of-site issue.[25] It is likely that laser technology will continue to evolve and alleviate these issues, but at present, lasers are limited to short-range, mostly defensive weapons.

Laser Remote Sensing

Remote sensing is another way in which directed-energy supports military operations. It is a technique for measuring and monitoring objects without making physical contact with that object.[26] It can provide accurate and timely mapping data of land and ocean surfaces. In addition, remote sensing gives military planners significant advantages by allowing observations of hazardous and contested areas. Recently, directed-energy technology has proven to be one of the most efficient and economical ways to conduct remote sensing, from both air and space based platforms. [27]

Laser Imaging Detection and Ranging (LIDAR) is one of the most common remote sensing techniques. LIDAR is an active, electro-optical, remote sensing system, used for 3D imaging and mapping, which works on the same principle as radar. It projects laser light to an object, that object subsequently interacts with and modifies the laser light. Some of the light reflects back to the LIDAR system, allowing analysis of the received data. Changes in the reflected light’s properties determine certain characteristics of the target object. These characteristics may be color, size, shape, or chemical makeup. Therefore, LIDAR data supports 3D terrain mapping, battle damage assessment, and can detect chemical agents, IEDs, and landmines. In addition, space based LIDAR platforms may soon assist missile warning and missile defense systems.[28] Furthermore, its ability to support intelligence and long distance strikes enhances and accelerates decision-making processes.

Robotics and autonomous vehicles are rapidly becoming a component of military arsenals. Currently, robots and autonomous vehicles are dependent on LIDAR technology to see their operating environment. LIDAR sensors build points of reference by using lasers to measure distance to objects. They accomplish this by sampling up to 1.5 million points of reference per second. This sampling rate enables robots and autonomous vehicles to detect objects and create 3D models. Software then categorizes and reacts to the LIDAR provided information.[29] Without the use of LIDAR technology, robotic and autonomous vehicles lack the ability react to objects in their environment.

There are limitations to LIDAR technology, because it relies on the measurement of time for a laser beam pulse to return to a sensor. If the target object has a highly reflective or absorptive surface, it may scatter the laser beam’s return to the sensor. Environmental factors can also affect LIDAR readings. Fog, snow, and rain can scatter the emitted laser pulse. In addition, LIDAR’s relatively slow refresh rates can cause significant problems for robots and autonomous vehicles. For example, when an autonomous vehicle moves at a fast rate of speed, LIDAR has difficulty discerning objects. [30] The most substantial drawback for LIDAR technology is the exorbitant price tag. However, the costs should dramatically decrease as it gains popularity in civilian robotics and autonomous vehicles.[31]

Laser Communications

Today’s militaries require the transmission of immense volumes of secure data, to numerous locations across the globe. In the past twenty years, militaries have considerably increased the use and broadcast of Intelligence, Surveillance, and Reconnaissance (ISR) imagery, video data, C2 data, UAS transmissions, and encrypted information. These demands increase congestion of the radio spectrum, thus creating a communications logjam. In order to conduct its peacetime mission, the U.S. military must share blocks of the electromagnetic spectrum with several commercial providers.[32] Ever increasing bandwidth requirements will soon necessitate different methods of communications for both civilian and military users.

Laser communications, also known as free space opticals, provide an alternative to traditional radio wave communications. Lasers can communicate information without the use of radio waves or fiber cable. They conduct line-of-site communications, by sending high bandwidth data to receivers on concentrated beams of light.[33] Although laser communications technology is in its infancy, it appears to be gaining traction.[34] Interest in laser communications has steadily grown in the private sector, and its proponents proclaim that it is ready for military use. Lasers have already successfully performed communications from ground-to-ground, ground-to-airplane, ground-to-satellite, and satellite-to-satellite.[35] Recently, several defense contractors have begun developing laser communications technology for both military and civilian use.[36]

Laser communications provide numerous advantages over traditional radio or fiber communications. They are not susceptible to electromagnetic interference (EMI), do not produce stray signals, and are substantially lighter than most radiofrequency (RF) systems. Laser communications also have the ability to transmit enormous quantities of data, at a rate of 100 to 1,000 times faster than traditional RF systems. Furthermore, laser communications provide a covert method of voice and data transmission. Traditional radio transmissions are easy to jam, geo-locate, and de-encrypt, while laser communications are nearly impossible to trace or intercept. [37]

Laser communications have limitations and technological challenges. Varying environmental conditions, such as heavy fog, smoke, or high temperatures, can degrade laser communication links. In addition, lasers are limited to point-to-point and line-of-site communications. However, similar to the challenge with DEWs, the future use of reflectors and relay stations on vehicles, ships, aircraft, and satellites may mitigate laser communication shortcomings. Another limitation is that they only work for short-range transmissions. However, the U.S. military has successfully experimented with ground, air, sea, and undersea laser communications links to mitigate this issue.[38] Despite current limitations, future technological developments will allow lasers to become a vital means of communication.

The Way Ahead

Since the 1960s, few military technologies have held as much promise as directed-energy. Early failures led to program defunding. However, today’s directed-energy technologies have reached a point of operational maturity.[39] Technological advances may soon solve directed-energy challenges, such as weather, power loss, and line-of-site restrictions. The U.S. military must recognize that directed-energy technology will soon replace contemporary weapons and communications systems. In order to move forward, the U.S. military should establish the same clear guidelines, doctrine, training, organizations, and funding streams that it provides to traditional weapons.[40]

The U.S. military should take the following actions to move forward with directed-energy technologies: fully fund development programs, conduct an assessment of directed-energy’s use against future threats, encourage cooperation with other federal departments, and facilitate the sharing of directed-energy technologies with allies. Although directed-energy research is progressing, insufficient funding has hampered its development and deployment. The U.S. military has voiced praise for directed-energy technologies, but has not always been enthusiastic with funding. The military must move on from mere words of praise, and begin to fully embrace development.[41] Furthermore, it must identify and categorize potential threats that directed-energy technology can defeat. Matching a requirement gap to a potential directed-energy technology will help increase awareness and funding. In order to create greater efficiency in directed-energy technology, the DoD should establish cooperative programs with other agencies and departments, such as the Department of Homeland Security (DHS), Department of Justice (DOJ), Department of Energy (DOE), and the intelligence community. Cooperation amongst federal entities can accomplish more, at an increased speed. Failure to cooperate on development will result in duplicate research, redundancy, increased cost, and less production. Finally, the U.S. should begin a dialogue concerning directed-energy with its partners and allies, to not only share technology, but also work towards consensus on its military use.[42]

Conclusion

Directed-energy technology is already an indispensable component of the military and has tremendous potential for the future. The evidence indicates that directed-energy will soon become the most significant technology for success on the battlefield. Directed-energy technologies support warfighting enablers, such as robotics, information technology, space technology, and drones. Moreover, it is the best defense against new threats, such as cyber warfare, missile proliferation, armed drones, and small boat swarms. Directed-energy technologies can also support many new operational tasks, such as curtailing the number of ground troops, reducing collateral damage, long distance strikes, and improved situational awareness. Finally, directed-energy can support weapons platforms and communications systems located in all war-fighting domains. In order to meet new challenges on the battlefield, the U.S military should immediately embrace the war-fighting potential that directed-energy technologies possess.

* This article is an excerpt from LTC Siegfried Ullrich’s original research project for the United States Army War College, Carlisle Barracks, PA.

Lt. Col. Sig Ullrich is an Army Reservist and Department of the Army Civilian assigned to the Army Space and Missile Defense School.

Endnotes

[1] Alane Kochems and Andrew Gudgel, “The Viability of Directed-Energy Weapons,” The Heritage Foundation Online, no. 1931(April 28, 2006): 1, http://www.heritage.org/missile-defense/report/the-viability-directed-energy-weapons (accessed November 23, 2017).

[2] U.S. Joint Chiefs of Staff, Electronic Warfare, Joint Publication 3-13.1 (Washington DC: U.S. Joint Chiefs of Staff, January 25, 2007), 106, https://fas.org/irp/doddir/dod/jp3-13-1.pdf (accessed November 28, 2017).

[3] David Hayes and Elizabeth Quintana, “When Will Directed Energy Weapons See The Light?,” The RUSI Journal 156, no. 3 (June 21, 2011): 64.

[4] Skyler Frink, “Communicating at the Speed of Light: Laser Technology Enables High-Bandwidth Communications and Imagery,” Military and Aerospace Electronics Online, June 6, 2012, 2, http://www.militaryaerospace.com/articles/2012/06/laser-communications-feature.html (accessed November 29, 2017).

[5] Hemani Kaushal and Georges Kaddoum, “Applications of Lasers for Tactical Military Operations,” IEEE Explore Digital Library 5, no. 1 (September 22, 2017): 40, http://ieeexplore.ieee.org/document/8048469 (accessed November 27, 2017).

[6] Stephen Chen, “US Lasers? PLA Preparing to Raise its Deflector Shields,” South China Morning Post Online, March 10, 2014, http://www.scmp.com/news/china/article/1444732 (accessed December 15, 2017).

[7] U.S. Joint Chiefs of Staff, Electronic Warfare, 106.

[8] Hayes and Quintana, “When Will Directed,” 64.

[9] Kochems and Gudgel, “The Viability,” 2.

[10] Mark M. Rich, “Sonic Weapons,” in New World War: Revolutionary Methods for Political Control (Morrisville, NC: Lulu Enterprises, 2011), 139, http://www.newworldwar.org/dewintro.htm (accessed December 12, 2017).

[11] Kyle Mizokami, “How the Military will be Revolutionized By Laser Weaponry,” Popular Mechanics Magazine Online, March 11, 2016, 4, http://www.popularmechanics.com/military/weapons/news/a19877/how-the-military-will-be-revolutionized-by-laser-weaponry (accessed November 22, 2017).

[12] Kaushal and Kaddoum, “Applications of Lasers,” 45.

[13] United States Army Acquisition Support Center (USAASC), Instrumentable – Multi Integrated Laser Engagement System (I-MILES), 3, http://asc.army.mil/web/portfolio-item/instrumentable-multiple-integrated-laser-engagement-system-i-miles/ (accessed December 12, 2017).

[14] Kochems and Gudgel, “The Viability,” 4.

[15] Kaushal and Kaddoum, “Applications of Lasers,” 41.

[16] John Marshall, “A Horrifying New Laser Weapon That the World Should Ban Now,” The New York Times Online, April 12, 1995, 1, http://www.nytimes.com/1995/04/12/opinion/12iht-edmar.html (accessed December 12, 2017).

[17] Hayes and Quintana, “When Will Directed,” 66.

[18] International Institute for Strategic Studies (IISS), “Directed Energy Weapons: Finally Coming of Age?,” The Military Balance Online 115, no. 1 (January 2015): 9.

[19] Jason B. Cutshaw, “Army Demonstrates Integration of laser Weapon on Combat Vehicle,” March 17, 2017, 1, https://www.army.mil/article/184353/army_demonstrates_integration_of_laser_weapon_on_combat_vehicle (accessed December 12, 2017).

[20] Kris Osborn, “Navy to fire 150Kw ship laser weapon from destroyers, carriers,” We Are The Mighty Online, January 24, 2017, http://www.wearethemighty.com/articles/navy-to-fire-150kw-ship-laser-weapon-from-destroyers-carriers (accessed November 27, 2017).

[21] SpaceNews Editor, “NRO Confirms Chinese Laser Test Illuminates U.S. Spacecraft,” SpaceNews, October 3, 2006, 1, http://spacenews.com/nro-confirms-chinese-laser-test-illuminated-us-spacecraft/ (accessed November 27, 2017).

[22] Kazuto Suzuki, “Satellites, the Floating Targets,” The World Today Online (February and March 2016): 16, https://www.chathamhouse.org/system/files/publications/twt/Satellites,%20the%20floating%20targets.pdf (accessed November 27, 2017).

[23] Mizokami, “How the Military,” 9-10.

[24] Ibid., 11.

[25] Kochems and Gudgel, “The Viability,” 5.

[26] Langley Research Center, “Remote Sensing and Lasers,” Langley News Online, March 1998, 1, https://www.nasa.gov/centers/langley/news/factsheets/RemoteSensing.html (accessed November 28, 2017).

[27] Ibid., 1.

[28] Kaushal and Kaddoum, “Applications of Lasers,” 41.

[29] Comet Labs, “What is LIDAR and How Does it Help Robots See?,” Robotics Trends Magazine Online, April 8, 2016, 2, http://www.roboticstrends.com/article/what_is_lidar_and_how_does_it_help_robots_see (accessed December 12, 2017).

[30] Ibid., 4.

[31] Steve Arar, “The Race to Affordable LiDAR,” April 9, 2017, https://www.allaboutcircuits.com/news/the-race-to-afforable-lidar/ (accessed December 12, 2017).

[32] Stew Magnuson, “Laser Communications to Thwart Jamming, Interception,” National Defense Magazine, November 1, 2014, 2, http://www.nationaldefensemagazine.org/articles/2014/11/1/2014november-laser-communications-to-thwart-jamming-interception (accessed December 12, 2017).

[33] Frink, “Communicating at the Speed,” 3.

[34] Ibid., 3.

[35] Ibid., 5.

[36] Magnuson, “Laser Communications,” 2.

[37] Magnuson, “Laser Communications,” 3.

[38] Kaushal and Kaddoum, “Applications of Lasers,” 43.

[39] Paul Scharre, “Can Lasers Save America’s Military Dominance?,” The National Interest Online, April 19, 2015, 2, http://nationalinterest.org/feature/can-lasers-save-americas-military-dominance-12669 (accessed November 27, 2017).

[40] Kochems and Gudgel, “The Viability,” 10.

[41] Scharre, “Can Lasers Save,” 1.

[42] Jack Spencer and James J. Carafano, “The Use of Directed Energy Weapons to Protect Critical Infrastructure,” The Heritage Foundation Backgrounder Journal Online, no. 1783, (August 2, 2004): 5-6, http://www.heritage.org/defense/report/the-use-directed-energy-weapons-protect-critical-infrastructure (accessed December 16, 2017).