The combustion tap-off cycle is a power cycle of a

bipropellant rocket A liquid-propellant rocket or liquid rocket utilizes a rocket engine that uses liquid propellants. Liquids are desirable because they have a reasonably high density and high specific impulse (''I''sp). This allows the volume of the propellant t ...

engine An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power ...

. The cycle takes a small portion of hot exhaust gas from the rocket engine's

combustion chamber A combustion chamber is part of an internal combustion engine in which the fuel/air mix is burned. For steam engines, the term has also been used for an extension of the firebox which is used to allow a more complete combustion process. Intern ...

and routes it through

turbopump A turbopump is a propellant pump with two main components: a rotodynamic pump and a driving gas turbine, usually both mounted on the same shaft, or sometimes geared together. They were initially developed in Germany in the early 1940s. The purpo ...

turbines to pump fuel before being exhausted (similar to the

gas-generator cycle The gas-generator cycle is a power cycle of a pumped liquid bipropellant rocket engine. Part of the unburned propellant is burned in a gas generator (or preburner) and the resulting hot gas is used to power the propellant pumps before being exh ...

). Since fuel is exhausted, the tap-off cycle is considered an open-cycle engine. The cycle is comparable to a gas-generator cycle engine with turbines driven by main combustion chamber exhaust rather than a separate gas generator or preburner. The J-2S rocket engine, a cancelled engine developed by NASA, used the combustion tap-off cycle and was first successfully tested in 1969. By 2013, Blue Origin, with their

New Shepard New Shepard is a fully reusable suborbital launch vehicle developed by Blue Origin for space tourism. The vehicle is named after Alan Shepard, the first American astronaut in space. The vehicle is capable of vertical takeoff and vertical lan ...

launch vehicle, had successfully flight-tested the

BE-3 The BE-3 (''Blue Engine 3'') is a LH2/ LOX rocket engine developed by Blue Origin. The engine began development in the early 2010s, and completed acceptance testing in early 2015. The engine is being used on the New Shepard suborbital rocket, ...

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. In contrast, the upper-stage variant of the BE-3, the BE-3U, uses an

expander cycle The expander cycle is a power cycle of a bipropellant rocket engine. In this cycle, the fuel is used to cool the engine's combustion chamber, picking up heat and changing phase. The now heated and gaseous fuel then powers the turbine that drives ...

to power the turbopump, and will be used on the upper stage of the New Glenn launch vehicle.BE-3 test update
Blue Origin, 10 August 2018, accessed 15 August 2018]. The Reaver 1 engine in Firefly Alpha uses a tap-off cycle. It first flew in September 2021 then made it to orbit on its second attempt in October 2022.

References

{{Thermodynamic cycles Combustion Rocket engines Spacecraft propulsion Thermodynamic cycles

See also

References