Response of Heatshield Material at Stagnation Point of Pioneer-Venus Probes

The ablation, pyrolysis gas formation and removal, and heat conduction phenomena at the stagnation point of theheatshieldforthefourPioneer-Venusprobevehiclesarecalculated.Themotionofthepyrolysisgasiscalculated by solvingthemassand momentum equationsforthegas,accountingforfrictionandinertial forces. Thedeveloped computer code gives satisfactory results when applied to two ground-based cases and one e ight-test case. For the calculation of the Pioneer-Venus e ight cases, recently calculated values of convective and radiative heating rates are used. Good agreement is seen in thermocouple temperature for the day probe and north probe for which the entry angle and e ight trajectory are known. For the night probe and large probe, for which entry angle and e ight trajectory are unknown, agreement is poor.