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Nautilus Tactical High Energy Laser

The cooperative Tactical High Energy Laser (THEL) Demonstrator ACTD was initiated by a memorandum of agreement between the United States and the Government of Israel on 18 July 1996. The THEL is a high- energy laser weapon system that uses proven laser beam generation technologies, proven beam- pointing technologies, and existing sensors and communication networks to provide a new active defense capability in counterair missions. The THEL can provide an innovative solution not offered by other systems or technologies for the acquisition and close-in engagement problems associated with short- to medium-range threats, thereby significantly enhancing coverage of combat forces and theater-level assets. The THEL low-cost per kill (about $3,000 per kill) will also provide a cost-effective defense against low-cost air threats. It features up to 60 shots without reloading and a P(k) near 1 at ranges of some 5 km.

A joint U.S.-Israeli program was initiated to develop a THEL demonstrator using deuterium fluoride chemical laser technologies. THEL uses a Deuterium-Fluoride (DF) laser. NF3 and C2H4 are first reacted in multiple, side-by-side, high-pressure combustion chambers using an oxidizer (NF3) rich mixture that generates free F atoms. After ignition the combustion-generated F atoms, mixed with combustion by-products and a He diluent, flow into the laser cavity. A mixture of He and deuterium is also injected into the laser cavity, and DF is generated in an excited state as deuterium reacts with the free F atoms. The laser cavity is now ready to produce a laser beam.

THEL uses both Hydrogen Peroxide and Nitrogen Trifluoride. Nitrogen Triflouride (NF3) NF3 is used as a fluorine source in high-energy chemical lasers. Two applications are THEL and MIRACL (Mid-Infrared Advanced Chemical Laser) at White Sands Missile Range. Type 70 Hydrogen Peroxide is a critical element in the Anti-Ballistic Laser (ABL) and THEL Programs. Chemical lasers are the only class of HEL able to achieve megawatt power levels at century's turn. The MIRACL is a deuterium fluoride (DF) laser operating at a wavelength of 3.8 microns that has been in operation at the megawatt level since the mid 1980s at the White Sands HEL Systems Test Facility. It suffered from inherent propagation losses at full power in the operational wavelengths. DF technology found a home in the US Army/Israeli THEL, where propagation losses were mitigated by lower power levels and a crossing target.

Questions remained as to how well the THEL would operate on a battlefield with smoke and dust. The principal loss mechanism is a nonlinear process called thermal blooming, in which energy absorbed in the air creates a negative lens that defocuses the beam. Increasing the power of the beam increases the energy absorbed and worsens the problem. Thermal blooming is nonlinear; it evolves over a horizontal path that has atmosphere all the way to the target. Therefore, closed loop adaptive optics techniques are ineffective.

The U.S. and Israeli THEL team members completed a Concept Design Review in Israel for the demonstrator. Approximately 21 months was planned to design and build the system, followed by 12 to 18 months of field testing at the High Energy Laser Systems Test Facility in Israel. This program delivered a THEL Demonstrator by 1998 with a limited operational capability to defend against short-range rockets. The THEL weapon system concept definition studies using advanced technologies were awarded to four contractors on 30 September 1996. The prime contractor for THEL is TRW.

THEL conducted test firing in FY1998, and Initial Operational Capability (IOC) was planned in FY1999. The THEL ACTD was successfully completed in October 2000. The THEL demonstrator is a complete fixed site weapon system which includes a HEL beam generator, based on deuterium fluoride chemical laser (DFCL) technologies; an acquisition, pointing, and tracking system; and a battle management system, including an organic fire control radar.

THEL tests during 2000 and 2001, which focused on the threat of rockets, proved highly successful, intercepting and destroying 25 Katyusha rockets. Parameters of major interest, which were systematically explored in these field tests, include the engagement range, the aspect angle between the rocket axis and the laser beam, the elevation angle of the engagement, the target slew rate, and other engagement parameters important for an operational system.

THEL was transferred to the US Army's Program Executive Office for Air, Space and Missile Defense (PEO-ASMD) in 2003 for further development. The demonstrated effectiveness of the fixed site THEL demonstrator led to the initiation of a system engineering trade study in FY01 to evaluate mobile THEL variants that meet both Israeli and US Army mission needs. At that time, the Tactical High-Energy Laser (THEL) represented the low-risk, low-cost approach to field a high-energy laser system with operational capability of value in defending against air and missile attacks on forces, urban areas, or critical infrastructure. The DF laser demonstrated, in tests, effectiveness in destroying Katyusha rockets and airborne targets, including simultaneous engagements of both airborne and rocketlaunched targets. THEL was the first laser weapon system developed by the United States.

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