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New storable fuel upper-stage propulsion system

Space Systems engineers have developed an upper-stage engine demonstrator for the European Space Agency (ESA). Results of the recently completed test campaign are promising; the engine meets all requirements to replace other models currently in service, such as on the Vega rocket.

Although engines that run on storable fuel are a core competency of German-European aerospace engineering, none are currently being produced in the three to eight kN (kilonewton) thrust class. To close this gap, ESA commissioned Airbus Defence and Space to develop a technology demonstrator. This autumn, after a short development and production phase, a team of young space engineers put the demonstrator through extensive testing with success: “Weve proven that our engine demonstrator works and that it meets all requirements,” says Torben Birck, a systems engineer.

During testing, the team used dinitrogen tetroxide (NTO) for the first time to cool one section of the combustion chamber. According to Torben, this had never been done in Europe before. They cooled another section of the combustion chamber using monomethylhydrazine (MMH). The advantage of using this combination of fuels is that MMH and NTO ignite on contact with each other, so no separate ignition is required. Whats more, both substances can be stored at room temperature.

The team also redesigned the injection elements and the absorber. “For engines that run on storable fuels, high frequency vibrations are a major problem,” explains Torben. But not for the Airbus DS demonstrator. “We put a lot of effort into the design and behaviour of the injectors and the special absorber. Our demonstrator is so far proving to be very robust.”

60 tests have been carried out on the engine, which has an outer diameter of approximately 15 cm and is 32 cm in length (without nozzle extension). It burned for a total of 420 seconds during the testing process. “Our hope now is that ESA will grant us a development contract. Now that we have proof of what the engine can do, the outlook is good,” says Torben. The engine could also be used in landers and kick stages for missions to other planets, for example.

Propulsion systemESAAirbus Defence and Space