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The most impressive thing about their rockets are the motors they use. All modern liquid rocket motors use turbo pumps to pressurize liquid fuel and drive it i

The most impressive thing about their rockets are the motors they use. All modern liquid rocket motors use turbo pumps to pressurize liquid fuel and drive it into the combustion chamber. All other rockets use some fuel to run a turbine that powers the pumps, with the variations being how that entire system is piped together. The Rocket Lab motor, Rutherford, uses a lithium ion battery and electric motor to power the pumps. This reduces the amount of fuel required to lift cargo into space by about 10% compared to SpaceX’s already impressive Merlin 1D motors. Also, they 3D print them in 24 hours, all in one part (sans electronics I suppose). Which is incredibly impressive.

jandrese 8y ago
3D printing them in 24 hours is impressive. I've had some toys barely bigger than my arm that take longer than that to print. Obviously these rocket engines are using a totally different technology, but it's still really impressive that they are able to build them so quickly.
Gravityloss 8y ago
A fuel burning turbine is much more mass efficient than a lithium battery powered one. And hence also makes the whole vehicle more fuel efficient. But a turbine is much harder to develop and manufacture. Especially at small scale, the turbine is also inefficient so it has less advantage to a battery there. It wouldn't make sense to run the Falcon 9 pumps with batteries.
- Kye 8y ago
  I wonder how a hybrid approach like they do with freight trains would work. Generate electricity with energy-dense fuel, then use that to drive electric motors.
  - Gravityloss 8y ago
    Hard to find any energy denser fuels than the ones they already use for main propulsion. But yes, with a hybrid one, you could decouple the rotation rate of the turbine and the pumps. They have different optimal points. Or you could have more pump stages with different speeds. Some engines use gears for this purpose (NK-33). Some engines use two turbines, one for each pump (SSME). Also startup would be nice and easy.
    - Kye 8y ago
      >> "Hard to find any energy denser fuels than the ones they already use for main propulsion." I phrased that poorly. I meant fuel as a class of things compared to relatively sparse batteries.
      - Gravityloss 8y ago
        Ah yes. Still, Soyuz uses different fuel to drive the pumps from the main propellants. Hydrogen peroxide monopropellant for pumps, liquid oxygen and kerosene for main propellants. This is V-2 heritage. Back then the turbine materials were not developed yet that could take the high heat.

jandrese 8y ago

3D printing them in 24 hours is impressive. I've had some toys barely bigger than my arm that take longer than that to print. Obviously these rocket engines are using a totally different technology, but it's still really impressive that they are able to build them so quickly.

Gravityloss 8y ago

A fuel burning turbine is much more mass efficient than a lithium battery powered one. And hence also makes the whole vehicle more fuel efficient. But a turbine is much harder to develop and manufacture. Especially at small scale, the turbine is also inefficient so it has less advantage to a battery there. It wouldn't make sense to run the Falcon 9 pumps with batteries.

Kye 8y ago
I wonder how a hybrid approach like they do with freight trains would work. Generate electricity with energy-dense fuel, then use that to drive electric motors.
- Gravityloss 8y ago
  Hard to find any energy denser fuels than the ones they already use for main propulsion. But yes, with a hybrid one, you could decouple the rotation rate of the turbine and the pumps. They have different optimal points. Or you could have more pump stages with different speeds. Some engines use gears for this purpose (NK-33). Some engines use two turbines, one for each pump (SSME). Also startup would be nice and easy.
  - Kye 8y ago
    >> "Hard to find any energy denser fuels than the ones they already use for main propulsion." I phrased that poorly. I meant fuel as a class of things compared to relatively sparse batteries.
    - Gravityloss 8y ago
      Ah yes. Still, Soyuz uses different fuel to drive the pumps from the main propellants. Hydrogen peroxide monopropellant for pumps, liquid oxygen and kerosene for main propellants. This is V-2 heritage. Back then the turbine materials were not developed yet that could take the high heat.