Rutherford (rocket engine)
Sea-level Rutherford engine
|Country of origin||United States|
|Application||First- and second-stage engine|
|Propellant||LOX / RP-1|
|Cycle||Electric pump-fed engine|
|Pumps||2 electric pumps|
|Thrust (vac.)||5,400 lbf (24 kN)|
|Thrust (SL)||5,400 lbf (24 kN)|
|Isp (vac.)||First stage: 311 s (3.05 km/s)|
Upper stage: 343 s (3.36 km/s)
Rutherford is a liquid-propellant rocket engine designed by American-New Zealand aerospace company Rocket Lab and manufactured in California. It uses LOX and RP-1 as its propellants and is the first flight-ready engine to use the electric-pump feed cycle. It is used on the company's own rocket, Electron. The rocket uses a similar engine arrangement to the Falcon 9; a two-stage rocket using a cluster of nine identical engines on the first stage, and one vacuum-optimized version with a longer nozzle on the second stage. The sea-level version produces 24 kN (5,400 lbf) of thrust and has a specific impulse of 311 s (3.05 km/s), while the vacuum optimized-version produces 24 kN (5,400 lbf) of thrust and has a specific impulse of 343 s (3.36 km/s).
Rutherford, named after renowned British-based, New Zealander scientist Ernest Rutherford, is a small liquid-propellant rocket engine designed to be simple and cheap to produce. It is used as both a first-stage and a second-stage engine, which simplifies logistics and improves economies of scale. To reduce its cost, it uses the electric-pump feed cycle, being the first flight-ready engine of such type. It is fabricated largely by 3D printing, using a method called electron-beam melting. Its combustion chamber, injectors, pumps, and main propellant valves are all 3D-printed.
As with all pump-fed engines, the Rutherford uses a rotodynamic pump to increase the pressure from the tanks to that needed by the combustion chamber. The use of a pump avoids the need for heavy tanks capable of holding high pressures and the high amounts of inert gas needed to keep the tanks pressurized during flight.
The pumps (one for the fuel and one for the oxidizer) in electric-pump feed engines are driven by an electric motor. The Rutherford engine uses dual brushless DC electric motors and a lithium polymer battery. It is claimed that this improves efficiency from the 50% of a typical gas-generator cycle to 95%. However, the battery pack increases the weight of the complete engine and presents an energy conversion issue.
Each engine has two small motors that generate 50 hp (37 kW) while spinning at 40 000 rpm. The first-stage battery, which has to power the pumps of nine engines simultaneously, can provide over 1 MW of electric power.
The engine is regeneratively cooled, meaning that before injection some of the cold RP-1 is passed through cooling channels embedded in the combustion chamber and nozzle structure, transferring heat away from them, before finally being injected into the combustion chamber.
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