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Space Based Laser [SBL]

The potential to intercept and destroy a missile over enemy territory soon after launch, rather than over friendly territory, makes the development of a boost phase intercept (BPI) capability very desirable. In concert with ground based theater missile defense (TMD) systems already under development, the U.S. continues to investigate BPI concepts for BMD systems.

The SBL program could develop the technology to provide the U.S. with an advanced BMD system for both theater and national missile defense. BMDO believes that an SBL system has the potential to make other contributions to U.S. security and world security as a whole, such as inducing potential aggressors to abandon ballistic missile programs by rendering them useless. Failing that, BMDO believes that the creation of such a universal defense system would provide the impetus for other nations to expand their security agreements with the United States, bringing them under a U. S. sponsored missile defense umbrella.

An SBL platform would achieve missile interception by focusing and maintaining a high powered laser on a target until it achieves catastrophic destruction. Energy for the sustained laser burst is generated by the chemical reaction of the hydrogen fluoride (HF) molecule. The HF molecules are created in an excited state from which the subsequent optical energy is drawn by an optical resonator surrounding the gain generator.

Lasers have been studied for their usefulness in air defense since 1973, when the Mid Infrared Advanced Chemical Laser (MIRACL) was first tested against tactical missiles and drone aircraft. Work on such systems continued through the 1980s, with the Airborne Laser Laboratory, which completed the first test laser intercepts above the earth. Initial work on laser based defense systems was overseen by the Defense Advanced Research Projects Agency (DARPA), but transferred to the newly created Strategic Defense Initiative Organization (SDIO) in 1984. Work continues today under the auspices of the BMDO, the successor to the SDIO.

The SBL program builds on a broad variety of technologies developed by the SDIO in the 1980s. The work on the Large Optics Demonstration Experiment (LODE), completed in 1987, provided the means to control the beams of large, high powered lasers. The Large Advanced Mirror Program (LAMP) designed and built a 4 meter diameter space designed mirror with the required optical figure and surface quality. In 1991, the Alpha laser (2.8 mm) developed by the SDIO achieved megawatt power at the requisite operating level in a low pressure environment similar to space. Numerous Acquisition, Tracking, and Pointing/ Fire Control (ATP/ FC) experiments both completed and currently underway will provide the SBL platform with stable aimpoints. Successes in the field of ATP include advances in inertial reference, vibration isolation, and rapid retargeting/ precision pointing (R2P2). In 1995 the Space Pointing Integrated Controls Experiment offered near weapons level results during testing.

Most recently, the Alpha LAMP Integration (ALI) program has performed integrated high energy ground testing of the laser and beam expander to demonstrate the critical system elements. The next step is an integrated space vehicle ground test with a space demonstration to conclusively prove the feasibility of deploying an operational SBL system.

Future plans include orbiting the SBL Readiness Demonstrator (SBLRD) in order to test all of the systems together in their intended working environment. Designs for the SBLRD satellite call for four major subsystems: the ATP system; providing acquisition, tracking, targeting, stabilization, and assessment capabilities; the laser device, providing the optical power, and beam quality, as well as maintains nozzle efficiency; the optics and beam control systems, enhancing and focus the beam, augmenting the capabilities of the laser device; and the space systems, providing a stable platform, storage of the reactants, and furnish electrical power (but do not power the laser).

The SBLRD is intended to demonstrate the capability to perform boost phase Theater Missile Defense from space. The objectives of the space demonstration include gaining performance information critical to the development of an operational SBL system, as well as gain a general understanding of operating such a system.

BMDO and the Air Force agreed to transfer the execution of the SBLRD project and the related SBL technology developments to the Air Force. BMDO retained overarching SBL architecture responsibilities.

Alpha High Energy Laser (HEL)

Alpha LaserMegawatt class power levels were first achieved by the Mid-Infrared Advanced Chemical Laser (MIRACL) originally sponsored by the Navy, later by DARPA, and then by BMDO. Because the design was intended for sea level operation, the MIRACL laser does not achieve the optimum efficiency necessary for space-based operation. DARPA launched the Alpha laser program, with the goal of developing a megawatt level SBL that was scaleable to more powerful weapon levels and optimized for space operation. In this design, stacked cylindrical rings of nozzles are used for reactant mixing. The gain generation assembly achieves higher power by simply stacking more rings. In 1991, the Alpha laser demonstrated megawatt class power levels similar to MIRACL, but in a low pressure, space operation environment. Alpha demonstrates that multi-megawatt, space-compatible lasers can be built and operated.

Large Advanced Mirror Program (LAMP)

To demonstrate the ability to fabricate the large mirror required by an SBL, the Large Advanced Mirror Program (LAMP) built a lightweight, segmented 4 m diameter mirror on which testing was completed in 1989. Tests verified that the surface optical figure and quality desired were achieved, and that the mirror was controlled to the required tolerances by adaptive optics adjustments. This mirror consists of a 17 mm thick facesheet bonded to fine figure actuators that are mounted on a graphite epoxy supported reaction structure. To this day, this is the largest mirror completed for use in space. This LAMP segmented design is applicable to 10 m class mirrors, and the Large Optical Segment (LOS) program has since produced a mirror segment sized for an 11 m mirror. The large dimension of this LOS mirror segment approximates the diameter of the LAMP mirror

Beam Control- Large Optics Demonstration Experiment (LODE) and ALI

The ability to control a beam was demonstrated at low power under the Large Optics Demonstration Experiment (LODE) in 1987. The current high power beam control technology is now being integrated with the Alpha laser and the LAMP mirror in a high power ground demonstration of the entire high energy laser weapon element. This is known as the Alpha-LAMP Integration (ALI) program.

Acquisition, Tracking, Pointing (ATP)

The ATP technologies required (sensors, optics, processors, etc.) have been validated through a series of component and integrated testing programs over the last decade. In 1985, the Talon Gold brassboard operated sub-scale versions of all the elements needed in the operational ATP system including separate pointing and tracking apertures, an illuminator, an inertial reference gyro system, fire control mode logic, sensors and trackers. Talon Gold achieved performance levels equivalent to that needed for the SBL. In 1991, the space-borne Relay Mirror Experiment (RME), relayed a low-power laser beam from a ground site to low-earth orbit and back down to a scoring target board at another location with greater pointing accuracy and beam stability than needed by SBL. The technology to point and control the large space structures of the SBL was validated in 1993 by the Rapid Retargeting and Precision Pointing (R2P2) program that used a hardware test bed to develop and test the large and small angle spacecraft slewing control laws and algorithms. The Space Pointing Integrated Controls Experiment (SPICE) demonstrated in 1995 near weapon scale disturbance isolation of 60-80 db and a pointing jitter reduction of 75:1. In 1998, the Phillips-Laboratory-executed High Altitude Balloon Experiment, (HABE) will demonstrate autonomous end-to-end operation of the key ATP-Fire Control (FC) functions in a realistic timeline against actual thrusting ballistic missiles. HABE will use a visible low-power marker beam as a surrogate to the megawatt HF beam and measure beam pointing accuracy, jitter and drift against a fixed aimpoint on the target.

Current SBL planning is based on a 20 satellite constellation, operating at a 40° inclination, intended to provide the optimum TMD threat negation capability. At this degree of deployment, kill times per missile will range from 1 to 10 seconds, depending on the range from the missile. Retargeting times are calculated at as low as 0.5 seconds for new targets requiring small angle changes. It is estimated that a constellation consisting of only 12 satellites can negate 94% of all missile threats in most theater threat scenarios. Thus a system consisting of 20 satellites is expected by BMDO to provide nearly full threat negation.

SBLRD Characteristics
Weight: 17,500 kg Length: 20.12 m
Diameter: 4.57 m Mirror Diameter: 4.0 m

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