Regolith Derived Heat Shield for a Planetary Body Entry and Descent System with In-Situ Fabrication

Within the scope of the testing to date, the feasibility of using extraterrestrial regoliths as the construction material for atmospheric entry heat shields has been confirmed from the results of the acetylene flame and arc jet testing. While some of the arc jet-tested samples were heavily ablated, they provided adequate low temperatures on their rear surfaces. These rear surface peak temperatures were recorded several minutes after arc jet test termination. While the highest energy input (92 W/cm2) at a five minute duration was comparable to a space shuttle re-entry from low Earth orbit, interplanetary atmospheric entry energies can be on the order of about 300 W/cm2 or higher. For these type of atmospheric entries, a much thicker regolith derived heat shield would be required than the two inch thick samples evaluated. If the heat shield is fabricated on Phobos or an asteroid, where there is little gravity, then fairly large heat shields can be used to protect returning payloads to Earth. A number of sintered and RTV bound formulations were evaluated. However, samples of JSC-1 Mars with the larger RTV concentrations performed well. In future work, JSC-1 Mars will be replaced by a more representative simulant material using materials that represent characteristics of Phobos and Deimos materials instead. Other lunar material simulants that reflect anorthosite-rich highlands materials are also planned. Much mission architecture work still needs to be performed to determine the full cost/benefit of using regoliths as atmospheric heat shield material. Cost savings for a 20-mission Mars campaign (10 unmanned and 10 manned missions) are estimated to be about $35 billion dollars if the massive heat shields for each mission did not have to be transported from the surface of the Earth to Mars.