J-2X (Engine)

The J-2X is a modern gas generator cycle, bi-propellant rocket engine, planned for use in the Ares I and Ares V launch vehicles. It consumes liquid hydrogen and liquid oxygen. It has its origin in the J-2 rocket engines used by the Saturn Ib and Saturn V launchers. It is produced by Pratt and Whitney Rocketdyne.

Differences from the J-2

Schematic of the J-2X

While the J-2 was a gas-generator cycle or open cycle rocket engine, the J-2X uses so called tap-off cycle for powering its turbopumps. In such a cycle, a small part of the hot exhaust gases from the combustion chamber is used for powering the two turbopump assemblies. These turbopumps are connected in series with a hot-gas duct. After passing the oxidizer turbopump, the hot gases are directed into the nozzle exhaust stream.

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