Application
Reusable rocket launcher vehicles

Sponsor
European Space Agency

Product or Service Supplied
Research, development and testing

Problem
The move towards reusable rocket launcher vehicles, coupled with the need for increased payload in rocket powered space vehicles, is driving rocket engine development to produce smaller, more durable turbo-pumps, operating at higher speeds and pressures. This enormous design challenge, requiring improvements in seal materials, and new seal design strategies, was the subject of a consortium project sponsored by the European Space Agency.

Objectives
Seals in these future turbo-pumps, which supply high-pressure liquid oxygen and hydrogen to the combustion nozzles, will be required to operate under more stringent conditions whilst wearing less.

Seal Operating Conditions
In a liquid oxygen turbo-pump, power is provided to the pump by a turbine mounted at the other end of the same shaft and driven by hot hydrogen-rich gas. Absolute separation of the pumped propellant and the driving gas is essential to avoid ignition and catastrophic failure. The dynamic sealing system (DSS) of the propellant turbo-pump is one of the most critical components in liquid rocket engines. Helium is used as a barrier gas to purge the zone between seals which adds to the engine weight and detracts from the payload.

Approach
BHR Group developed a range of specialised FEA based programs, CFD models and the design for a high-speed hot gas and cryogenic tribological test facility for investigating the surface contact and thermal and mechanical stresses that occur. Initial studies into new surface finishes for the mechanical seal have been undertaken and CFD models used to predict and where possible minimise the Helium requirement.

Outcome/Benefits
Progress to date has concentrated on identifying suitable technologies and materials for high-speed cryogenic tribological testing and also predicting the consumption of Helium barrier gas. This data will be used to design and manufacture seals for liquid oxygen and gaseous hydrogen applications.

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