MARS PATHFINDER 6-DEGREE-OF-FREEDOM ENTRY ANALYSIS

The Mars Pathfinder mission provides the next opportunity for scientif ic exploration of the surface of Mars following a 7.6 km/s direct entr y: In support of this effort, a six-degree-of-freedom trajectory analy sis and aerodynamic characteristic assessment are performed to demonst rate vehicle flyability and to quantify the effect that each of numero us uncertainties has upon the nominal mission profile. The entry vehic le is shown to be aerodynamically stable over a large portion of its a tmospheric flight. Two low angle-of-attack static instabilities (frees tream velocities of about 6.5 and 3.5 km/s) and a low angle-of-attack dynamic instability (supersonic) are identified and shown to cause bou nded increases in vehicle attitude. The effects of center-of-gravity p lacement, entry attitude, vehicle roll rate, aerodynamic misprediction , and atmospheric uncertainty on the vehicle attitude profile and para chute deployment conditions are quantified. A Monte Carlo analysis is performed to statistically assess the combined impact of multiple off- nominal conditions on the nominal flight characteristics. These result s suggest that there is a 99.7% probability that the peak attitude thr oughout the entry will be less than 8.5 deg, the peak heating attitude mill be below 6.2 deg, and the attitude at parachute deployment will be less than 3.9 deg.