• Adharit

Why electric pumps are the future of rocket engine combustion cycles

Rocket engines use different types of plumbing systems to drive fuel and oxidizer into the combustion chamber. Gas generator cycle, staged combustion cycle, full flow staged combustion cycle are some of the "primitive" cycles. They are still used in most of modern rockets.

These cycles have their own advantages and disadvantages. The major disadvantage of these cycles are that they are very complex and difficult to manufacture. Electric pump cycles on the other hand do not have these complexities

Rocket lab's Rutherford engine is the first rocket engine to use the electric pump fed cycle. Nine of them power their Electron rocket's first stage and a single vacuum optimized engine for the second stage

Rutherford engine only weighs 35kg and uses RP-1 as fuel (which is kerosene). It generates 25kN of thrust with sea level specific impulse of 311 seconds.

This engine uses a Li-Po battery which powers a brush less DC motor

(the DC from battery is converted to AC with the help of an inverter to send it into motor).

The motors generate about 37kW of power while spinning at 42,000 RPM! The first stage battery which powers nine engines can produce up to 1 MW of electric power.

The electric pumps send both the fuel and oxidizer into the combustion chamber without all the complexities involved in the previous engines. The fuel is also used for regenerative cooling.

Also the Rutherford engine is manufactured by 3D printing or Electron Beam Melting (which is like 3D printing, more about it in next blog) hence making it easier to manufacture. Rocket lab claims that they can manufacture an engine every 24 hours!

Hence with all these advantages and improvement in batteries will make electric pump fed cycles more accessible for the startups

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