Building blankets for satellites

The GSTP with Rostock System-Technik and the Fraunhofer Institute, Germany, have taken the first steps to developing a space-qualified adjustable thermal blanket made from phase change materials.

The blankets are intended to offer a new design solution for passive thermal control systems, which could be used on spacecrafts.

More than ten different applications for the blankets were identified, including using them to increase solar cell efficiency, which would lead to improvements for future launchers and Low Earth Orbit satellites. On the Launcher Upper Stage, using one of these types of blankets showed that the electrical output of the solar cells mounted on it could be increased by around 11 per cent, with a very small impact on mass.

To develop the blanket, the activity used ethanol as the phase change material and demonstrated that ethanol can be safely stored between the foils and withstands the stresses caused under vacuum conditions. Ethanol is advantageous as it means the thermal blankets are able to withstand the freezing temperatures required. The issue of ethanol having a low thermal conductivity was solved by surrounding it with a highly conductive material – a perforated aluminum foil was used as as nanoporous matrix and it was sealed with aluminum foil also.

The blankets are flexible and to increase the performance several foils can be superimposed thermally coupled with each other.

The activity was conducted as part of GSTP’s de-risking framework, which aims to unblock barriers in the way of larger critical technologies.

Due to residual gas inside the ACPB test samples no clear indication of a phase change could be detected during the thermal performance tests under vacuum conditions, most probably due to a ballooning effect of the blankets.

For future developments of thermal hardware based on this technology, the activity suggested continuing to use ethanol, and that the blankets must be filled gas-free in order to achieve a high thermal performance. Suitable technologies must be identified for this process, the optimal structure of the blankets and the choice of materials must be determined and verified.

 G617-241TAbx De-risk assessment: Adjustable Cryo PCM blanket completed in April 2020.