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Rutherford
	Sea-level Rutherford engine
Country of origin	United States; New Zealand
Designer	Rocket Lab
Manufacturer	Rocket Lab
Application	First- and second-stage
Status	Active
Liquid-fuel engine
Propellant	LOX / RP-1
Cycle	Electric-pump-fed
Pumps	2
Configuration
Chamber	1
Performance
Thrust, vacuum	Original: 24 kN (5,500 lbf); Updated: 26 kN (5,800 lbf);
Thrust, sea-level	Original: 24 kN (5,500 lbf); Updated: 25 kN (5,600 lbf);
Thrust-to-weight ratio	72.8
Specific impulse, vacuum	343 s (3.36 km/s)
Specific impulse, sea-level	311 s (3.05 km/s)
Dimensions
Diameter	.25 m (9.8 in)
Dry mass	35 kg (77 lb)
Used in
	Electron, HASTE
References
References

Rutherford is a liquid-propellant rocket engine designed by aerospace company Rocket Lab^[8] and manufactured in Long Beach, California.^[9] The engine is used on the company's own rocket, Electron. It uses LOX (liquid oxygen) and RP-1 (refined kerosene) as its propellants and is the first flight-ready engine to use the electric-pump-fed cycle. 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. This arrangement is also known as an octaweb.^[10]^[5]^[6] The sea-level version produces 24.9 kN (5,600 lbf) of thrust and has a specific impulse of 311 s (3.05 km/s), while the vacuum optimized-version produces 25.8 kN (5,800 lbf) of thrust and has a specific impulse of 343 s (3.36 km/s).^[11]

First test-firing took place in 2013.^[12] The engine was qualified for flight in March 2016^[13] and had its first flight on 25 May 2017.^[14] As of April 2024, the engine has powered 47 Electron flights in total, making the count of flown engines 369, including one engine flown twice.^[15]

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.^[5]^[6] To reduce its cost, it uses the electric-pump feed cycle, being the first flight-ready engine of such type.^[4] 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.^[16]^[17]^[18]

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.^[4] 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.^[19]

The pumps (one for the fuel and one for the oxidizer) in electric-pump feed engines are driven by an electric motor.^[19] 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%.^[20] However, the battery pack increases the weight of the complete engine and presents an energy conversion issue.^[19]

Each engine has two small motors that generate 37 kW (50 hp) while spinning at 40 000 rpm.^[20] The first-stage battery, which has to power the pumps of nine engines simultaneously, can provide over 1 MW (1,300 hp) of electric power.^[21]

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.