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This article was Originally Published on Jul 10, 2003 in Volume: 2  Issue: 3

Directed Energy

AFRL looks at laser possiblities across the spectrum.

By Deborah Mercurio

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Lasers emerged in 1958 as new and novel devices, and over the years they have appeared in countless science-fiction movies to entertain the masses. Fiction has become fact as scientists at Kirtland Air Force Base, Albuquerque, NM, and around the world continue to research and develop laser technologies.

Much has evolved from the first appearance of lasers. Today, gases, liquids and solids are used to create lasers. Some are as small as a grain of sand and some are as large as a football field. In general, they have become smaller, lighter and more powerful. As scientists continue their research, laser applications continue to grow. The Air Force Research Laboratory’s (AFRL) Directed Energy Directorate has been developing technologies that have reached, or are near, fruition. The work at the directorate began in the early 1960s when the Advanced Research Projects Agency issued Order 313-62 to the Air Force Systems Command (now the Air Force Materiel Command) to investigate lasers.

A task force, at the Air Force Weapons Laboratory (now the Air Force Research Laboratory’s Directed Energy Directorate), was formed in 1966 to study the feasibility of laser systems for weapons applications.

Research in the 1970s resulted in the building of a tri-service laser at the Starfire Optical Range. A contract for an airborne pointer/tracker was initiated with Hughes Aircraft Co., and the Airborne Laser Laboratory design effort was also initiated with General Dynamics Corp. The first high-energy laser beam was generated from a gas dynamics laser. The technology development at the end of the 1970s resulted in the completion of ground testing for the Airborne Laser Laboratory.

In the 1980s, the first engagement against a tube-launched, optically tracked, wire-guided missile (TOW) target at the White Sands Missile Range was completed, resulting in the first high-energy laser beam ever fired from an aircraft in flight. The first attempt at an AIM-9 Sidewinder air-to-air missile engagement was carried out at China Lake Naval Air Station in Ridgecrest, CA, on May 28, 1981.

In July of 1983, the Air Force announced a major milestone in weapons development with the successful engagement of the Airborne Laser Laboratory’s NC-135, the military version of Boeing’s 707. The aircraft was modified to use a carbon-dioxide laser against AIM-9 missiles.

Five missiles were successfully destroyed. Two months later, the Airborne Laser Laboratory successfully engaged a BQM-33A drone at low altitude over the Pacific. It was the final target engagement of this program.

The Airborne Laser Laboratory program was completed in 1984. It provided the Air Force invaluable insight into the disciplines and technologies of beam control, atmospheric effects, optical component integration, lightweight structures and pointing and tracking that are vital to laser research today. It also showed that a laser mounted on an aircraft could be an effective defensive weapon.

“The Airborne Laser Laboratory created the path of opportunity for today’s directed-energy systems,” said Colonel Mark W. Neice, chief of the Directed Energy Directorate’s Laser Division. “It is the program that allowed other programs to emerge.”

As a tool for the warfighter, lasers can pinpoint a target from a cluttered environment of non-targets to destroy only what is selected. Collateral damage, if not completely eliminated, can be reduced greatly as carefully measured amounts of energy are delivered, said Neice.

Laser research and development work at the directorate includes work with the chemical, solid-state, and diode lasers. Research in these and other areas will determine the laser power source of the future.

According to Dr. Kip R. Kendrick, program manager for the Advanced Tactical Laser, the directorate has done extensive work with a chemical laser invented there in 1977, which can be scaled to mega-watt power levels generating its energy through chemical reaction. It is considerably compact compared to the carbon-dioxide laser, a kilowatt-class system that was used on the Airborne Laser Laboratory.

The Chemical Oxygen Iodine Laser’s (COIL) energy is created by the chemical reaction between energetic oxygen and iodine molecules when they are mixed. The laser propagates at 1.315 microns in the infrared spectrum. The wavelength travels easily through the atmosphere and has greater brightness or destructive potential on a target.

The COIL had been implemented in a new concept of operations, the Airborne Laser (ABL). The ABL, a Missile Defense Agency program, involves the use of the COIL on a modified Boeing 747-400 freighter-series aircraft to destroy ballistic missiles during their boost phase.

In addition to this laser, there are three other important lasers aboard the aircraft: the Active Ranger System, which provides preliminary tracking data; the Track Illuminator Laser, which produces more refined tracking data; and the Beacon Illuminator Laser which measures the amount of atmospheric disturbance.

The development of this revolutionary use of a directed-energy system as a weapon, rather than as a targeting or range-finding apparatus, should change how our country will be able to defend itself.

“A near-term application is putting the COIL on tactical platforms, such as a C-130,” said Kendrick. Ideally, this will evolve to a C-130 gunship and eventually lead to lasers on fighter-type platforms. With a sealed exhaust system, chemicals are not ejected overboard and zeolites—a substance that acts as a gas sponge—allows for gas to be stored in a small volume, added the senior scientist. An Advanced Concepts Technical Demonstration (ACTD), sponsored by the Air Force’s Special Operations Command, is planned for completion in December 2006.

Kendrick said the AFRL’s Advanced Tactical Laser Technology Development Program is developing technology in parallel with the Special Operations Command and Boeing to enhance the capabilities of the Advanced Tactical Laser.

The advantage chemical lasers now have over solid-state lasers is in the amount of energy produced, however, research and development with solid-state lasers include improving their power levels.

Currently, the state-of-the-art solid-state laser has an operational power of 2 to 3 kilowatts. The Directed Energy Directorate, with the Army and the High Energy Laser Joint Technology Office, is involved in a program to develop a 25-kilowatt solid-state laser, said Neice. The eventual goal of this joint project is to demonstrate the laser at this power level in 2005, and ultimately, a solid-state laser at 100 kilowatts in 2007.

If the goal is reached, the solid-state laser could become the laser of choice for directed-energy weaponry over the chemical laser because of its smaller size, larger magazine and no concerns for chemical management, such as chemical waste stream. Chemical mixing and wasting complicates the logistics trail and is undesirable for battlefield operations, said Neice.

All branches of the military are interested in the use of the solid-state laser, said Neice. The Army is interested in it as an element of Future Combat Systems, the Navy is interested in its use for ship-based defense, and the Marines are interested for its capability in area defense. The Air Force’s interest relates to airborne applications, such as fighter aircraft, as well as space-based applications.

According to Neice, other laser research and technology development being accomplished at the directorate involves the study of lasers and sensors working together to detect and defend large platforms dealing with air-mobility and air-refueling missions. This work is under the umbrella of the Large Aircraft Infrared Counter Measures  (LAIRCM) program.

“The focus is to improve the laser and extend the range,” Neice said. He further explained that protection against all threats including, short-range, rocket- propelled grenades and shoulder-launched missiles, known as man-portable air defense (MANPAD) systems, is being investigated.

“Infrared missiles are a threat, and our work deals with directing lasers to defeat those vulnerable spots of the missiles,” said Neice.

Work with the Focal Plane Array, a new type of missile seeker consisting of a two-dimensional array of detectors that creates an image from light, has been conducted with the different branches of the military and a team from the British Ministry of Defence at the directorate. This joint team has been testing surrogate missiles and the countermeasures used against them.

“Designed to better attack an aircraft and reject flares, the detectors can see what the human eye cannot,” said Donald J. Smith, the directorate research physicist who has headed some of these experiments.

According to Smith, the detectors are placed on the front end of the missile and act like the eye’s retina electronically transferring an image to the computerized brain of the missile where the information is processed guiding the missile to impact.

Fiber lasers, light through a fiber, is yet another area of concentration for the Directed Energy Directorate’s laser division. Because fiber lasers are good for heat distribution, easily transmit laser light and are robust, they have proven effective in daily applications such as medical, welding and repair work.

For the medical arena, the laser medical pac and laser medical pen, both developed in-house, provide medical personnel with a unique, compact, portable and battery-operated laser capability. The laser can cut like a scalpel and coagulate bleeding. The military applications for these items are with advance trauma life support on the battlefield and can be used by special operations and pararescue personnel.

Laser energy is delivered to the medical pac by a fiber-optic cable that provides very intense power at the tip of the instrument. The output wavelength is 808 nanometers with an output power of 8 1/2 watts.

As a directed energy system, fibers are worth exploring for future weapon applications. The primary application for this type laser is development of high-energy lasers for tactical weapons that could be incorporated into current platforms using only electricity as the energy source. The major technical challenge is to coherently combine many of these single mode fiber lasers to achieve kW or greater laser systems.

Solid-state lasers use diodes to pump gain material, such as crystal or glass. Diode lasers, also known as semi-conductor lasers and closely related to the light-emitting diodes that provide the red numeral and letter displays on some calculators, are small and can be mass-produced relatively inexpensively.

Diodes are compact and are very efficient at converting electrical power to laser light. Due to their narrow emission bandwidth, they reduce the thermal loading of the laser crystals and allow higher powers to be extracted, said Captain Steven M. Massey, program manager for the directorate’s special projects section.

The (diodes are reliable and have an approximate lifetime of 10,000 hours, said the laser physicist. The research and technology development in this area is focused on fiber-coupled diode lasers as efficient small sources of excitation energy for a solid-state laser which could lead to small, lightweight, efficient, high-average power lasers as battlefield weapons.

The Directed Energy Directorate places great emphasis on integrating and transitioning research technologies into military systems used by operational commands and maintained by the Air Force Materiel Command.

The laser division is the United States Air Force’s center of expertise for developing high-energy lasers and getting those technologies to U.S. military forces.

The Davis Advanced Laser Facility, a research facility for the Air Force Research Laboratory’s Directed Energy Directorate, is used for research development of chemical, electrical and hybrid lasers that can be used in air-, ground-, and space-based systems.

The facility consists of six major laboratories, along with several smaller ones, a chemistry laboratory, an electronics laboratory and two conference rooms. The interior configuration is such that it can be rearranged to fit the needs of new experiments. Two of the laboratories are dedicated to chemical laser work. The other four laser laboratories are used for solid-state or electrical laser research.

The Directed Energy Directorate is located at the Phillips Research Site, Kirtland Air Force Base, NM. In addition to laser development, the directorate is committed to high-power microwave and advanced optics and imaging technologies.

The mission of the directorate is to develop innovative and advanced directed-energy technologies that will provide instant defeat and instant detection of adversaries. The vision of the directorate is one that provides the U.S. military forces with “speed-of-light” battlespace dominance.  O

Deborah Mercurio is with the Air Force Research Laboratory’s Directed Energy Public Affairs Office.

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