Ariane 5 main stage oxygen tank pressurization

Abstract

BACKGROUND The oxygen tank of Ariane 5 main stage is pressurized with helium, stored on board in a cryogenic vessel at very low temperature, 4 10 K (7 18R). The helium pressurant is conditioned by a heat-exchanger before being introduced into the tank through flow control valves. System and component designs are based on SEP and subcontractor's know-how. Specific functional and technological challenges, due to cryogenic helium storage, characterize this system. L'Air L i p i d e is in charge of the development and production of the liquid helium storage, the main innovation of the system. The oxygen tank of Ariane 5 main stage is pressurized during flight with helium gas. The helium pressurant is stored on board in a cryogenic storage, filled on the ground with liquid helium. During all the mission, helium is maintained at very low temperature 4 10 K (7 WR), to assure a sufficient stand-by time with limited pressure rise. The cryogenic liquid storage was selected owing to weight savings attributable to this system, compared to more conventional concepts. Trade studies in 1988 pointed out a weight reduction of a b u t 400 kg (SSO Ibm) in comparison with a high pressure helium gas storage at 300 bars (4350 psi) and 90 K (160'R) ; the reduction was still of 200 kg (440 Ibm) for a high pressure storage at 200 bars (2900 psi) and 20 K (36R). Design is progressively validated and perfected by models and component testing . Open-loop tests of the pressurization system are performed in 1992 on Vulcain engine test bench.