||Wright-Patterson AFB, OH 454337542
Hypersonic flights lead to high temperature flows, air dissociation, and cumulative heating of air-frames. Consequently, the performance of all on-board sensor systems such as GPS, telemetry, communication, command and control, radar, ladar, and electro-optical sensors are all adversely affected to varying degrees by the hypersonic environment. Further, the dynamic range of parameters that characterize the environment is quite large and is strongly influenced by many factors including altitude, velocity, duration of flight, geometry of the vehicle, airframe, and heat-shield material. The parameters that characterize the flow can vary by several orders during the course of a trajectory. Hence, sensor systems encounter a variety of situations. Some of the issues encountered include signal attenuation, signal distortion due to turbulent flow, radiation from heated optical windows, and emission from hot flows. An adaptive sensor system which uses a diagnostic tool to sense and adaptively match to the environment will be desirable. The boundary layer flow can be dispersive, inhomogeneous, fluctuating, and lossy. This poses challenges to wideband sensor systems using conformal arrays. With arrays we also face the problem of mutual coupling and impedance mismatch effects on beam forming. Moreover, the signal transmitted from the vehicle may be sufficiently intense to initiate nonlinear processes in the flow. The rapid maneuvers and high velocity place limitations on the integration time of the processing algorithms of the receivers. The requirements and issues associated with RF and EO/IR sensors are quite different. For instance, the hot window can radiate at infrared frequencies and the hot flow fields can emit and absorb at optical frequencies thereby seriously affecting the performance of EO/IR sensors on board. Research opportunities exist in the analyses and mitigation of the above-mentioned issues confronted by sensors aboard hypersonic platforms.
Turbulent hypersonic flow; Diagnostic tools; Adaptive sensors; Nonlinear processes; Optical windows; EO/IR imaging; SAR imaging; Moving target detection