Overall Preliminary Design of the Thermal Protection System for a Long Range Hypersonic Rocket-Powered Passenger Vehicle (SpaceLiner)

Kurzfassung

The long range hypersonic passenger transportation system SpaceLiner has been proposed by the Space Launcher Systems Analysis Group (SART) of the German Aerospace Center (DLR) and investigated in the frame of the European Commission project FAST20XX. The SpaceLiner is a two-stage fully reusable vehicle powered by rocket engines. It should carry about 50 passengers from Australia to Europe within 90 minutes. To accomplish a safe return to earth for all passengers in case of an emergency, the SpaceLiner passenger capsule can be separated from the rest of the vehicle and is then able to fly autonomously back to Earth. The focus of the paper is the sizing of both stages as well as the capsule’s passive thermal protection system. The SpaceLiner’s Thermal Protection System (TPS) has to withstand several different heat loads according to nominal flight and different abort cases. To be able to determine the heat loads for a full vehicle surface along different trajectories, fast engineering methods have to be used. The external heat flux was calculated by a fast code for preliminary flow analyses in hypersonic regime based on modified Newtonian surface inclination techniques and by using the Fay-Ridell equation close to the stagnation point and the Zoby-Moss-Sutton approach further downstream. The thicknesses of the different materials were optimized by using a 1D thermal conduction model. They depend heavily on the allowed temperature of the back-structure. According to the functional task and the chosen material, the structure is allowed to heat up to different maximum temperatures. Depending on the maximum temperature for the subdivided surface regions, different reusable materials were considered: CMC, TABI, AETB, AFRSI and FRSI. The TPS of the capsule, which is not part of the orbiter’s outer shell, is subject to high heat flux and has no need for re-usability. Therefore, an ablative thermal protection is preferred for stagnation and bottom areas with low system complexity, thus guaranteeing high safety. As an example, Avcoat was chosen. The paper shows the overall preliminary design of the TPS for a long range hypersonic rocket-powered passenger vehicle, comparing different materials and different back-structure temperatures.