Entry dispersion analysis for the Stardust Comet Sample Return Capsule

Stardust will be the first mission to return samples from a comet. The samp le return capsule, which is passively controlled during the fastest Earth e ntry ever, will land by parachute in Utah. The present study analyzes the e ntry, descent, and landing of the returning sample capsule. The effects of two aerodynamic instabilities are revealed (one in the high-altitude free-m olecular regime and the other in the transonic/subsonic flow regime), These instabilities could lead to unacceptably large excursions in the angle of attack near peak heating and main parachute deployment, respectively, To re duce the excursions resulting from the high-altitude instability, the entry spin rate of the capsule is increased from 5 to 16 rpm. To stabilize the e xcursions from the transonic/subsonic instability, a drogue chute with depl oyment triggered by a g-switch and timer is added prior to main parachute d eployment. A Monte Carlo dispersion analysis of the modified entry (from wh ich the impact of off-nominal conditions during the entry is ascertained) p redicts that the capsule attitude excursions near peak heating and drogue c hute deployment are within Stardust program limits. Additionally, the size of the resulting 3-sigma landing ellipse is 83.5 km in downrange by 29.2 km in crossrange, which is within the Utah Test and Training Range boundaries .