A supercritical helium pressurization tank for Ariane 5 [ Return towards  Space programs  ]

The technical challenge for Air Liquide lay in designing and producing the pressurisation system with supercritical tank control as the cornerstone. This 1,332 liter tank weighing only 224 kg is able to store the 166 kg of supercritical Helium required for flight at 23 bars. Its leak tightness is absolutely perfect which means the supercritical Helium can be contained at an absolute temperature of 4 Kelvin: even though it contains over 150 kg of Helium, less than one milligram of is likely to escape in a century. Furthermore, to provide a minimum 23 hrs of self-sufficiency after filling, the thermal insulation for this tank has been optimized so that it can withstand the ambient temperature at Kourou for 23 hrs followed by the high temperatures in flight while losing very small amounts of Helium through evaporation.
All material supplied is covered by a contract signed between Air Liquide and ASTRIUM with the approval of the European Space Agency.

The project is very demanding in terms of leak tightness. To meet this requirement, specialized materials had to be used and new welding processes qualified.
To limit thermal inputs, 30 layers of vacuum super-insulant were used on the one hand, and on the other the design was optimized while still guaranteeing resistance to the different stresses caused by the launch.