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Endoatmospheric Light Projectile (ENDO-LEAP)

The Strategic Defense Initiative (SDI) envisions the use of multiple tiers of non-nuclear weapons to provide an umbrella of protection from ballistic missiles. Operational engagement constraints typically require a high velocity interceptor in order to achieve reasonable protective coverage, and with an endo atmospheric intercept, this results in severe aerodynamic, aerothermal, and structural environments for the acquisition and homing phase of the intercept.

The SDI-related Endoatmospheric ('ENDO') LEAP program was charged with the development of very lightweight hypersonic velocity kinetic-kill homing projectiles for ballistic missile warhead interception. ENDO LEAP design development efforts encompass vehicle configuration, electrooptic and mm-wave homing seekers, attitude-control systems, airframe materials and fabrication methods, inertial-measurement units, software and signal processing systems, and power and electronic systems.

By 1992 the ENDO LEAP vehicle program was in the process of developing an interceptor which can operate successfully in this severe environment. The objective of the ENDO LEAP vehicle program was to design, develop, integrate and test vehicle technologies compatible with affordable lightweight interceptors to perform high and low endo atmospheric defense against ballistic missiles. These technologies were to be developed and tested in state-of-the-art testing facilities, such as the Large Energy National Shock Tunnel (LENS).

A program of fundamental, experimental research and analysis was conducted to design additional components necessary to modify, assemble and develop a ground-based facility (LENS) to duplicate flowfield environment around a hypersonic endo-atmospheric interceptor to evaluate optical seeker performance. Aero-optic instrumentation, used to measure the aero-optical characteristics of the viscous and shock layer over transpiration-and-filmed cooled nosetips at hypersonic speeds were also investigated. In the design of the facility, particular care was taken in designing the systems for a contamination-free hypersonic flow and in isolating the loads associated with the operation of the shock tunnel from the model support system and the aero-optic instrumentation.

Five instrumentation systems, including holography, imagery, boresight/jitter, radiometry and spectrometry were evaluated to provide consistent evaluation in ENDO-LEAP mission environments. State-of-the-art CFD codes with capabilities determining the inherent salient flowfield features such as turbulence and reacting chemistry were investigated and the GASP code was selected as the basic computational method. The stress levels and motion of shock tunnels were studied and analyzed using two approaches, a numeric marching code and a numeric solution to the wave equation. A flight test program based on existing sounding rocket technology was examined in order to design a high confidence flight test to validate the LENS ground test results.

In August 1992 the Strategic Defense Initiative Organization (SDIO) selected Lockheed Missiles & Space Company to continue work on the Endoatmospheric Light Exoatmospheric Projectile (ENDO-LEAP), by executing an option for Phase II of the program.

Work on Endo LEAP continued through 1995 under the Atmospheric Interceptor Technology (AIT) program.

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