Thermal design and performance of the Viking balloon-launched decelerator test vehicles

The thermal design and performance of the test vehicles used for the flight-qualification of the Viking parachute system are described. The desired range of test conditions was provided by a subsonic drop from a balloon altitude of 90,000 feet, and rocket-powered transonic and supersonic flights initiated at balloon altitudes of 120,000 feet. Unusual aspects of the thermal design approach included the application of techniques developed in support of planetary programs to the thermal analysis of balloon payloads and the use of ground firing data to establish realistic upper bounds for radiant plume heating during flight. The adequacy of thermal design is verified by flight data.