Ground Based Laser

The Strategic Defense Initiative concept envisioned a three-tiered defensive system - creating the ability to intercept a target missile in the boost, midcourse and terminal phases of its flight. By 1984, with over 25-years of experience in ballistic missile defense, the Army and more specifically this command, then known as the U.S. Army Strategic Defense Command (USASDC), was given the lead in most of the SDI programs. In the boost phase, the system incorporated a Boost Surveillance and Tracking System, the Space Based Laser and the Ground Based Laser. The Army shared responsibility for the SBL with the Air Force, while it was assigned sole control over the GBL.

On 2 April 1984, the SDIO authorized the laser imaging technology program. Two years later, on 26 March 1986, the USASDC created the GBL Project Office. Located at WSMR, New Mexico, the office oversaw the development of the ground-based free electron laser (FEL) technology integration experiment. As designed the laser would be several football fields long and situated on a 20-square mile site.

The goal was to develop a system that could intercept a target in the boost phase by bouncing the laser beam off relay mirrors based in space. Besides boost phase intercept capabilities, the projected benefits of a GBL system were target imaging and kill assessment, an unlimited magazine and target discrimination. According to SDIO'S 1984 directed energy weapon plan, research and development efforts on a ground-based laser were to have progressed by 1991 to the point where a decision could be made on whether to proceed with a system level demonstration, At this point, SDIO'S research program planned to have

• demonstrated the basic performance levels of (1) excimer and FEL beam generators, (2) a beam director with the capability to provide atmospheric compensation and propagate through the atmosphere at high powers, (3) large space relay optics, and (4) components needed to point relay optics accurately;
• selected the beam generator concept and completed its initial design;
• conducted integrated technology experiments that demonstrated high-power beam generators with a beam director providing atmospheric compensation at high-power;
• determined the feasibility of scaling to full weapon performance; and
• created a mature design of the space segments of the system level demonstration that included relay mirrors and an ATP subsystem with high level of accuracy.

SDIO was developing three different types of beam generators - induction FEL, radio frequency FEL, and excimer gas laser. The ground-based and the space-based laser projects were to share developments in large optics, beam control, and ATP. The plan specified that $1,721 million would be required for fiscal years 1986 through 1989 to perform the research and development to ready the ground-based laser for this decision point.

To this end, they explored the benefits of the radio frequency FEL and the more powerful induction FEL. By 1986, FEL systems had already demonstrated the most powerful laser to date operating at only 42% efficiency (converting electrical power into laser light). Initial tests showed that both approaches were feasible for full-scale development. The Project Office subsequently elected to proceed with a dual laser concept. As the project continued to progress, the SDIO and USASDC began to explore the possibility of using the laser as an anti-satellite (ASAT) system.

During 1986 and 1987, SDIO selected the Orogrande site at White Sands Missile Range in New Mexico for the ground-based laser and performed a detailed environmental impact statement. In 1987, SDIO awarded contracts for architectural and construction engineering support and for construction of facilities to support laser development. The facilities' contractor built an access road, three administrative buildings, and a communications center and laid water lines to the site. The facilities' contractor had also completed the designs for all other structures to be built at the site. These contracts were terminated in 1989 due to funding limitations. The facilities cost about $77 million and were being used by other activities at White Sands Missile Range.

SDIO conducted competition among three types of beam generators for the ground-based laser: excimer laser, radio frequency FEL, and induction FEL. SDIO designed and built a portion of the excimer gas laser device called Excimer Moderate Powered Raman Shifted baser Device and installed it at the High Energy baser Systems Test Facility at the White Sands Missile Range. The objectives of this program were to build and test an excirner laser to demonstrate the technology necessary for a high-power, repetitively pulsed, excimer laser and develop a theoretical model through a series of low-energy experiments. In 1989, SDIO eliminated the excimer laser as a candidate for the ground-based laser beam generator because of technical difficulties encountered during the White Sands Missile Range test, its low electrical efficiency, and the difficulty in propagating its short wavelength beam through the atmosphere. SDIO spent $169 million developing the excimer before it canceled the program.

A FEL uses electrons that have been "freed" from atomic nuclei and are accelerated to near the speed of light in a particle accelerator and then "wiggled magnetically" to produce a beam. A FEL produces a beam of radiant energy using a high-energy beam of electrons. The electrons travel through a special magnetic field that forces them to oscillate back and forth, causing the electrons to emit radiation. Unlike a regular laser beam, a FEL can be 'tuned' to any wavelength, from microwave to the ultraviolet" with research continuing to explore means to extend the range up to other parts of the spectrum. The FEL'S primary mission is to shoot down missiles in their boost and post-boost phases. Its primary advantage over the other directed energy weapons is that its output wavelength can be adjusted during operation to select those frequencies that propagate through the atmosphere with minimal problems.

After a formal a-year competition between teams composed of TRW/Lawrence Livermore National Laboratory and Boeing/Los Alamos National Laboratory, SD10 eliminated the induction FEL technology during fiscal year 1989 and selected the radio frequency FEL technology as the beam generator for the ground-based laser. In 1990, SDIO awarded a contract to Boeing Aerospace/Los Alamos National Laboratory to build a multimegawatt radio frequency FEL at the Orogrande site at White Sands Missile Range.

SDIO awarded a contract to Lockheed Missile and Space Company in 1987 for designing beam control and beam director systems for the ground-based laser. Because this contract was awarded before the radio frequency FEL was selected as the beam generator, Lockheed designed beam control systems for both the radio frequency and the induction FEM. The Lockheed contract, after costing $42 million, was terminated in 1989 due to funding limitations. SD10 also purchased a 3.6meter diameter, 6O-centimeter thick optical glass blank from Schott Glass Works for the ground-based beam director. It was cut into two 3CLcentimeter thick blanks. One blank is in storage and may be used in a space-based laser test stand in the future. The second blank was given to the Air Force for use in a telescope.

SDIO used the existing Mid-Infrared Advanced Chemical Laser and its associated Sea bite Beam Director to develop and demonstrate technology for atmospheric compensation of a ground-based laser beam director and for lethality, acquisition, and tracking experiments. This deuterium fluoride chemical laser was developed. and it is operated by the Navy at the High Energy Laser Systems Test Facility at the White Sands Missile Range. SDIO spent $110 million from fmcal years 1986 through 1989 for these technology development efforts. In addition, an experiment called the Sub-scale Atmospheric Blooming Experiment was performed at TRW's San Juan Capistrano test site, It demonstrated that adaptive optics systems can compensate for low-power thermal blooming distortions in the atmosphere.

In December 1990, SD10 decided that the FEL research would be reoriented toward determining the feasibility of a space-based FEL weapon. At this point, only one of the objectives included in the 1984 plan for a ground-based laser had been completed: SDIO had selected the radio frequency FEL as the beam generator and completed its initial high-power design. Technical progress, however, had been made on several other objectives for a ground-based laser system.

Los Alamos and Lawrence Livermore National Laboratories and Boeing Aerospace have achieved advances in the design and operation of FEL devices. Los Alamos demonstrated that (1) the photoinjector could produce electron beams with brightness levels needed for weapon class FELSa nd (2) efficiency improvements in energy recovery for radio frequency accelerators, which are required for efficient operation in space, could be made. Lawrence Liver-more demonstrated high efficiency energy extraction from a device called a "tapered wiggler" operating at short optical wavelengths. Boeing also demonstrated the operation of the FEL'S photoir\jector system by generating a high-quality electron beam with power in excess of 680 kilowatts for over 3 minutes, making it among the three highest average power electron accelerators in the world. SDIO spent $864 million from fiscal years 1986 through 1993 on FEL device development.

SDIO spent $1,244 million on this program, primarily for the ground-based laser, through fiscal year 1993. This amount represents about 72 percent of the $1,721 million SDIO believed was needed to do research for a ground-based system through fiscal year 1989. Funds were spent on preparing the ground site, conducting a competition for the beam generator, awarding a contract for designing a beam control and director systems, performing experiments on the optics and laser systems, and achieving progress in other technical areas such as atmospheric compensation.

Program redirections by SDI and repeated budget cuts, beginning in fiscal year 1988, however, forced frequent modifications and downscaling in the project. The dedication ceremony took place in July 1990. These events culminated in the eventual demise of the project in January 1991, six month after the official dedication ceremony for the new Ground-Based FEL facility.The USASDC completed termination of the Ground-Based Laser Project Office on 1 August 1991.

With the agreement of the SDIO, the Average Power Laser Experiment, a restructured version of the GBFEL, was transferred to the Directed Energy Weapons (DEW) Directorate. Research continued on laser programs under the auspices of the High Energy Laser Technology Division. In conjunction with this effort, the division also worked to evaluate the component design option of the FEL to use in a possible space-based FEL.