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High Velocity Interceptor Investigations

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Final rept.

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High velocity interceptors operating at low altitudes in the range from 20 to 30 km will experience a stressing aerothermal environment which can impact performance of the infrared sensordesignator system. This report addresses primarily two aspects of high velocity interceptors a novel passively cooled window concept and the control of boundary layer transition to turbulence. A totally new concept for maintaining the IR transmitting window of an interceptor at low temperature so as to minimize background interferences introduced by aerodynamic heating effects is described. The concept involves immersing a nest of fiber optics or bore-holes within a matrix of a low temperature pyrolysis material, a transition metal hydride. These hydrides have the ability to absorb heat at low temperatures through the desorption of H2 molecules and thus behave like low temperature, high energy ablators. Thermal response calculations show that our window concept is viable. The modeling of boundary-layer transition control over seeker windows under situations when the surface of the interceptor remains very cool during atmospheric flight is described. This occurs naturally for our passive cool window approach which employs a transition metal hydride to maintain window temperatures near 300 K at typical interceptor heating levels of several hundred watts per square centimeter. Such low surface temperatures provide a passive means of preventing boundary-layer transition from laminar to turbulent flow. A three-dimensional stability code was utilized to demonstrate that high-speed Mach 15 boundary layers on typical seeker head geometries are stabilized by extreme wall cooling.

Subject Categories:

  • Antimissile Defense Systems
  • Optical Detection and Detectors
  • Mechanics

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