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 the heatshield for the four Pioneer-Venus probe vehicles are calculated. The motion of the pyrolysis gas is calculated by solving the mass and momentum equations for the gas, accounting for friction and inertial forces. The developed computer code gives satisfactory results when applied to two ground-based cases and one flight-test case. For the calculation of the Pioneer-Venus flight 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 flight trajectory are known. For the night probe and large probe, for which entry angle and flight trajectory are unknown, agreement is poor.