Kestrel (rocket engine)

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SpaceX Kestrel engine.

The Kestrel engine is an RP-1/liquid oxygen pressure-fed rocket engine. The Kestrel engine was developed by SpaceX for upper stage use on the Falcon 1 rocket.

Kestrel was built around the same pintle architecture as the Merlin but does not have a turbo-pump and is fed only by tank pressure.

Kestrel is ablatively cooled in the chamber and throat and radiatively cooled in the nozzle, which is fabricated from a high strength niobium alloy. As a metal, niobium is highly resistant to cracking compared to carbon-carbon. An impact from orbital debris or during stage separation would simply dent the metal, but have no meaningful effect on engine performance. Helium pressurant efficiency is substantially increased via a titanium heat exchanger on the ablative/niobium boundary.

Thrust vector control is provided by electro-mechanical actuators on the engine dome for pitch and yaw. Roll control (and attitude control during coast phases) is provided by helium cold gas thrusters.

A TEA-TEB pyrophoric system is used to provide multiple restart capability on the upper stage. In a multi-manifested mission, this allows for drop off at different altitudes and inclinations.