NASP VEHICLE INTERACTIONS AND SIGNATURES ABOVE 100 KILOMETERS

As hypersonic space vehicles (such as the NASP X-30 Research Vehicle) traverse the 80-300 km altitude range, a variety of phenomena will ari se from the interaction of the spacecraft with the residual atmosphere . Across this altitude regime, the flow surrounding the vehicle makes a transition from continuum to free molecular. A simple modeling effor t is presented to quantify the variety of processes likely to occur. F or example, communications will be severely hampered by the enhanced p lasma cloud created at lower altitudes. Optical emissions will be gene rated in the high-velocity collisions of the atmospheric O, N2, and O2 With the vehicle surfaces and with outgassed molecules, transpired co olant, exhausts, and reflected atmospheric species. We have developed elementary gas kinetic descriptions of the flowfield and interaction l engths surrounding the lifting body vehicle. This information and assu med radiative efficiencies permitted predictions of relative radiance as a function of altitude. Quantitative predictions of the emissions f rom the ultraviolet through infrared spectral regions will occur and w ill result in decreased visibility of remote emission features. The lo cal interaction radiances are sufficiently bright to obscure emission from the upper atmosphere and will even substantially obscure the hard Earth in certain bands.