Experimental Simulation of High Enthalpy Planetary Entries

ABSTRACT

For the current exploration programs high enthalpy landing missions are foreseen. It is rather difficult to simulate the corresponding enthalpies with steady state facilities. For the case of sample return missions such as Genesis, STARDUST or Hayabusa hyperbolic entries require maximum enthalpies of about 80 MJ/kg. Atmospheric entry parameters of relevance were derived with the model of Allan and Eggers which was developed for ballistic capsules. The model was then extended by validated engineering equations for both convective and radiation heat flux. In addition, the integral for the total convective heat load and the upper Gamma function integrals for the integral radiation heat load were derived and solved. This provides the potential to assess parameters relevant within the test philosophy such as e.g. the test duration while having a material sample exposed e.g. under maximum heat flux conditions to the plasma. In this context it is shown that the high specific enthalpies can be reproduced using e.g. magnetoplasmadynamically driven plasma wind tunnels. Atmospheric entry missions at the planets, however, are accompanied by initial kinetic energies for the spacecraft that are at least in the order of half of the second power of the first cosmic velocity of the related planet. Corresponding specific enthalpies e.g. for the Jovian entry are by a factor of almost 8 higher than the enthalpies experienced within a hyperbolic Earth entry. The paper discusses potential facilities that can be used for the investigation of these entry missions.

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