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Mid-Infrared Advanced Chemical Laser (MIRACL)

The High Energy Laser Systems Test Facility (HELSTF) is located at White Sands Missile Range, New Mexico. HELSTF became operational on September 6, 1985 when the Air Force conducted the first Lethality and Target Hardening (LTH-l) program test for the Strategic Defense Initiative Organization (SDIO). HELSTF has been managed by the U.S. Army Space and Strategic Defense Command (USASSDC) since October 1990. Prior to that, the facility was under the command of Commander, White Sands Missile Range. Primary support for operation and maintenance of the SDC-managed facility is currently provided by Lockheed Engineering and Science Company (LESC). The Navy is responsible for the operation and maintenance of the MIRACL and the SEALITE Beam Director through its contractors, TRW and Hughes Aircraft.

HELSTF is designated as the Department of Defense (DoD) National Test Facility for high energy laser test and evaluation. HELSTF is the home of the Mid Infrared Advanced Chemical Laser (MIRACL), the United States' most powerful laser, which is a CW, megawatt class deuterium-fluoride laser operating in a band from 3.6 to 4.2 microns. In the more than ten years since operations began, HELSTF has supported a broad range of both laser and non-laser related test activities. High energy laser tests have included damage and vulnerability testing for all three uniformed services as well as materials and chemical research for industry and academia. HELSTF represents an approximate $800 million investment, with about $80 million of that in military construction funds.

The Mid-Infrared Advanced Chemical Laser (MIRACL) was the first megawatt-class, continuous wave, chemical laser built in the free world. It is a deuterium fluoride (DF) chemical laser with energy spectra distributed among about 10 lasing lines between 3.6 and 4.2 microns wavelength. Since it first lased in 1980, it has accumulated well over 3000 seconds of total lasing time. It remains the highest average power laser in the US.

MIRACL operation is similar to a rocket engine in which a fuel (ethylene, C2H4) is burned with an oxidizer (nitrogen trifluoride, NF3). Free, excited fluorine atoms are one of the combustion products. Just downstream from the combustor, deuterium and helium are injected into the exhaust. Deuterium combines with the excited fluorine to give excited deuterium fluoride (DF) molecules, while the helium stabilizes the reaction and controls the temperature. 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 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 cm square beam shape which is 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 SLBD.

Capabilities

  • Megawatt-class variable power, with good beam quality
  • Continuous-wave mid-infrared (3.8 microns)
  • Reliable operation demonstrated in more than 150 lasing tests and over 3000 seconds of lase time during the last decade.
  • 70 seconds maximum lase duration.

Programs Supported

  • Static Target Vulnerability Tests
    • Materials and Coatings
    • Aircraft and Missile Components
    • Effectiveness of Laser Hardening Techniques
  • Flying Target Vulnerability Tests
    • Subsonic and Supersonic Missile Engagements
  • Propagation Phenomenology
    • Effects of turbulence and thermal blooming on HEL beam propagation
    • Tracking in Presence of High-Power Beam
    • Effect of Obscurants
  • Laser Technology R&D
    • High-Power Adaptive Optics
    • Material Windows
    • Gratings and Coatings
  • HELLO Commercialization Tests
    • Advanced Coatings
    • Cloud Boring
    • Chemical Processing

Congress canceled the Navy SEALITE program, a self-defense lethality demonstration using the Mid-Infrared Advanced Chemical Laser (MIRACL), in the fall of 1983 and directed the MIRACL be installed at HELSTF to support a variety of tests for DoD. The SEALITE Beam Director (SLBD) is mounted on top of Test Cell 1. It consists of a large aperture (1.8 meter) gimbaled telescope and optics to point the MIRACL or other laser beam onto a target. The high power clear aperture is 1.5 meters. The remaining 0.3 meters is normally reserved for a tracker using the outer annulus of the primary mirror. The system is extremely agile and capable of high rotation and acceleration rates. The SLBD weighs 28,000 pounds, of which 18,000 are on the movable portion. The SLBD can also be used as a sensor platform.

The telescope is capable of focusing from a minimum range of 400 meters to infinity. A suite of infrared and visible sensors on the top of the gimbal (off axis from the HEL aperture) is used to acquire and track the target. These sensors look through a 40 cm telescope that can focus over the same range as the SLBD telescope and also correct for parallax between the two lines of sight. Boresight between the SLBD telescope and the sensor is maintained by an automatic laser alignment system. In addition, an aperture sharing element in the high power beam path makes it possible to track a target through the full 1.5 meter telescope aperture even when the high power beam is propagating.

These elements have been combined into an integrated system that can acquire and track targets at extended ranges, accept a very high energy beam, focus and aim the beam on a moving target, and keep this beam at the same position as long as necessary to destroy or disable the target. The SLBD has successfully engaged five BQM-34 drones as well as a supersonic Vandal missile, all at tactically significant ranges.

The SLBD system performs its pointing and tracking with a stabilized line-of-sight controlled by an inertially stabilized reference mirror and low-power alignment lasers and optical sensors. This scheme provides for high bandwidth, low jitter, and precise pointing of the MIRACL beam.

In addition to directing the high energy laser beam, the HELSTF SLBD has been used very successfully to passively track and image missiles in flight. The inherently precise pointing of the device and its ability to track very high speed targets make it an ideal platform for capturing in-flight imagery. The SLBD has been used as a sensor platform for tracking and imaging a number of Theater Missile Defense (TMD) launches and intercepts, including LANCE, ERINT, and LEAP. A 1000 frame-per-second, digital, infrared camera has been used to collect two-dimensional intercept measurements from targets and interceptors at over Mach 6 closure rates. Calibrated infrared sensors placed in the SLBD's optical train have been used to collect IR imagery for plume and hardbody thermal characterization.

Capabilities

  • High line-of-site rates and accelerations
  • Primary mirror diameter: 1.8m
  • Focus range: 400m to infinity
  • Primary track sensor: 8 to 12 micron FLIR
  • FLIR track sensor field of view: 4 X 5 micro radians
  • Shared aperture visible track sensor field of view: 0.3 X 0.3 micro radians

SLBD Passive Imaging Sensor Characteristics

         SENSOR      WAVE-    FIELD OF  ARRAY SIZE   FRAME RATE  APERTURE  
                     BAND     VIEW                                       
          LWIR       8-12 m   700 rad    128 x 128   up to 1000    1.5 m   
                                                        fps                
          MWIR        3-5 m   700 rad    128 x 128   up to 1000    1.5 m   
                                                        fps                
          FLIR       8-12 m    4 x 5      scanned    60 Hz/264     40 cm   
                                mrad                   lines               
        NFOV TV      visible  5 x 6.5    510 x 492   60 Hz/264     40 cm   
                                mrad                   lines               
        Wide FOV     visible 6.6 x 8.8   510 x 492     30 Hz       90 mm   
                                mrad                                       
     Wide FOV AMBER   3-5 m   12 mrad    128 x 128   up to 109     50 mm   
                                                         Hz                
     MIT High Frame  visible  100 rad     64 x 64     2000 Hz      1.5 m   
          Rate               to 1 mrad                                     
    

Tests Supported

  • 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 1.5m aperture
    • Radiometrically calibrated images
    • Spectral radiometry

Sources




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