Nitrogen Pressurization Subsystem for an Inflatable Structure
BRAVAIS, P¹; BUQUET, J¹; SANTERRE, B²; BONNEFOND, T²; DUPUY, C^3
1AIR LIQUIDE DTA; ²ASTRIUM ST; ³CNES

Air Liquide DTA has been awarded a contract by Astrium Space Transportation for the study and the development of a Nitrogen pressurization sub-system dedicated to IDEAS system. IDEAS, the Innovative Deorbiting Aerobrake System, is an aerobraking sail realised with the Gossamer technology, developed to allow the CNES Microscope Spacecraft to de-orbit within 25 years. The Nitrogen pressurization sub-system function is to deploy and rigidize the Gossamer structure.

After an initial trade off performed to select the best fluidic architecture (in terms of cost and mass), an architecture based on two pyrovalves arranged in a parallel lay-out, with 2 flow restrictors installed downstream each valve, has been selected. The first flow restrictor, a capillary one, allows to obtain the small flow rate required to deploy the masts whereas the second restrictor, a sonic hole, allows to obtain the large flow required to pressurize the masts within a small time to minimize the possible leak of the gossamer structure and thus the fluid budget. A nodal thermal model of the pressurisation sub-system coupled to CFD models of the nitrogen tank and the gossamer structure (cylindrical masts) have been developed to predict flow, pressure and temperature evolution inside each equipment of the pressurization sub-system and the Gossamer structure. The thermal model has been validated in part with a breadboard, in particular the flow restrictor characteristics and the pressure behaviour inside the nitrogen tank. The breadboard has also been used to validate the manufacturing process of the two flow restrictors.