Subsonic Dynamics of Stardust Sample Return Capsule

Subsonic dynamic stability tests performed in the NASA Langley 20-Foot Vertical Spin-Tunnel on a 0.238 scale model of the Stardust Sample Return Capsule are discussed. The tests reveal that the blunted 60 degree half-angle cone capsule is dynamically unstable at low subsonic conditions due to the aft location of the center-of-gravity (0.351 body diameters back from the nose). The divergent behavior of the capsule continued when the center-of-gravity was moved to 0.337 and 0.313 body diameters back from the nose. When the center-of-gravity was moved further forward to 0.290 body diameters back from the nose, the vehicle established itself in a limit cycle with amplitude around 10 degrees. Two afterbody modifications were examined which proved unsuccessful in alleviating the instability of the original design. Finally, the addition of different sized parachutes was examined as a means to stabilize the vehicle. The parachute tests indicate that a parachute with equivalent full scale drag area of at least 2.24 ft. is necessary to assure large perturbations are damped.