Description
Rutherford is named after renowned New Zealand-born scientist Ernest Rutherford. It 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 laser powder bed fusion, and more specifically Direct Metal Laser Solidification (DMLS®). 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 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.
