content 20-November-2017 16:08:34

EDM Thermal Protection System Tests

The EDM is protected during the entry phase by an aeroshell made of a sandwich structure (composite skins and aluminium honeycomb) and a Thermal Protection System (TPS).

The TPS material on the front and back shields is Norcoat-Liege. A few millimetres of this material (varying between 8 to 18 mm depending on the areas on the heat shield) is sufficient to insulate the interior of the EDM from heat on its external surface during EDL. The heat shield keeps the internal temperature below 170°C, which is then further reduced to about 50°C by more insulation.

Wind tunnel tests at Astrium's SIMOUN facility have confirmed the material's capacity to withstand the maximum heat flux expected to be encountered during Mars entry. A high-velocity plasma flow was used to reproduce the mechanical and thermal stresses encountered during entry. TPS samples, 420 mm wide and 150 mm long, as well as typical tiles of the heat shield and samples of the joints that fill the gaps between the tiles were tested at SIMOUN.

Thermal Protection System sample before and after plasma wind tunnel tests.
Credit: Astrium
Quantifying the erosion due to dust on the EDM's front shield. Credit: CNES, HPS, DLR

Apart from having to survive extreme thermo-mechanical loads during hypersonic entry, the EDM must also survive the highly dust-loaded atmosphere. At the time of arrival of the EDM at Mars in October 2016, the Red Planet will be experiencing its global dust storm season. This implies that the entire atmosphere will be dust-loaded for several months. None of the previous Mars missions have attempted to land during this season, making this a significant attempt in Mars exploration. This high dust concentration will erode the external layers of the TPS, reducing the insulation. To study this erosion, wind tunnel campaigns have been performed in mid-2010 at the DLR H2K wind tunnel where dust particles, similar to those at Mars, were injected at high velocities (about 2 kilometres per second).

The TPS test activities were carried out by EADS Astrium, led by Thales Alenia Space Italy and Thales Alenia Space France, under the close supervision of ESA.

Last Update: 25 February 2016

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