Reaction Control System Design Considerations for Mars Entry Vehicles

Summary • RCS can interfere with the aerodynamic characteristics of entry vehicle – Changes in aerodynamics occur in both supersonic and hypersonic segments of th t t j tthe entry trajectory • Control gain and aerodynamic cross coupling can occur• In extreme cases the authority of RCS can be negated – Computational and experimental analyses help bound the phenomena • Difficulties in both computational methods (wakes are hard to solve) and experiment (moments are small in comparisson to the forebody moments) • Impact of RCS on aerothermal evironments can be significant – Aeroheating increase by an order of magnitude depending on the specifics of theAeroheating increase by an order of magnitude depending on the specifics of the jet interaction– Impact on TPS selection, cost, schedule • Based on analyses performed to date, jet interaction with the flow around entry vehicle is better understood –  Paradigms have been developed to minimize destructive interference of RCS jets 11 3/12/2008 11