Abstract
An engineering analysis model for predicting the response and potential breakup of Cassini spacecraft nuclear fuel modules during accidental Earth reentries is described. Physical aspects considered include aerodynamics, aerothermodynamics, thermostructural loads and ablation response. The extreme velocity, 19 km/sec, of an inadvertent reentry during the Earth gravity-assist flyby requires the development of a new model to predict the dominant radiative heating rates. Uncertainty estimates are established for each of the major factors in the model. Sensitivity analyses are also carried out to determine the effect of off-nominal environments on the predicted outcome. This allows output from the calculations to be expressed as a probability density function for atmospheric fuel release. It is concluded that 18 to 36 percent of the nuclear fuel contained in the spacecraft will be released as respirable material if reentry occurs.
