NASA-LLIS-6342

Abstract

Protuberances and cavities can have a significant impact on both the structural and thermal loads of a spacecraft. The outer mold line (OML) of future spacecraft should be as clean as possible, and all protuberances and cavities should be eliminated or minimized. Definition of induced design environments for the Space Shuttle Vehicle presented a significant technical challenge when considering that in order to properly establish them, there was a need to not only define the detailed surface pressure distributions on protuberances and cavities, but also the aeroheating environment and the dynamic or fluctuating pressure field generated by these geometric features. Further, the presence of these protuberances and cavities generate effects on the near flow field as well as on surrounding surfaces. The Space Shuttle Program (SSP) embarked on the definition of these induced environments through analytical methods, subscale ground test of the mated vehicle as well as component level, and also numerical simulations. These efforts extended throughout the SSP life due to changes in protuberances (elimination and/or geometric shape changes to mitigate debris generation) or improvements in the methods (experimental and numerical) to better define design environments and reduce uncertainties. Cavities, in general, didn't change. At present, the accurate definition of induced design environments for protuberances and cavities remains a technical challenge even though significant advances in ground testing and numerical simulation models have occurred.