Combustion tap-off cycle

The cycle takes a small portion of hot exhaust gas from the rocket engine's combustion chamber and routes it through turbopump turbines to pump fuel before being exhausted (similar to the gas-generator cycle).

[2] By 2013, Blue Origin, with their New Shepard launch vehicle, had successfully flight-tested the BE-3 engine using a tap-off cycle.

According to Blue Origin, the cycle is particularly suited to human spaceflight due to its simplicity, with only one combustion chamber and a less stressful engine shutdown process.

However, engine startup is more complicated, and due to the hot gas fed from the main combustion chamber into the turbopumps, the turbine must be built to withstand higher-than-normal temperatures.

[3] In contrast, the upper-stage variant of the BE-3, the BE-3U, uses an expander cycle to power the turbopump, and will be used on the upper stage of the New Glenn launch vehicle.

Diagram of the open-cycle combustion tap-off rocket cycle. A small portion of exhaust from the combustion chamber is tapped off to power the turbine(s).