Why the Rutherford engine is the key to the Electron rocket

Video from the channel Mecánica Orbital about Electron, linked on its Above Ten Thousand entry. Duration: 12:49. Language: Spanish. Video type: Documentary.

The video explains the Rutherford engine, which powers Rocket Lab's Electron, and why it departs from the usual rocket engine design. It is still a chemical engine burning kerosene and liquid oxygen, but the pumps that feed the propellants into the combustion chamber are driven by electric motors powered by lithium batteries, instead of turbines driven by hot gas.

The Electron is a small two-stage launcher that has been flying regularly since 2017. It is designed for satellites weighing hundreds of kilograms that previously had to fly as secondary payloads on large rockets. Rocket Lab wanted an engine that could be built and tested quickly and that would allow frequent launches. Turbopumps, which work very well on heavy launchers such as the Saturn V, the Space Shuttle, the Falcon 9 or Starship, don't get simpler as they're scaled down. The video compares the Raptor, a full-flow staged-combustion engine several times taller than a person, with a Rutherford that Peter Beck, the company's founder, can hold in his arms.

The batteries deliver a lot of power during the few minutes of ascent and are discarded afterward; on the second stage they are released in flight. Much of the engine, including the combustion chamber with integrated cooling channels and the injectors, is 3D-printed in metal, which reduces parts and welds and makes it easier to modify the design. As drawbacks, the video points to the huge power demand and the dead weight of the batteries, which would make the system unworkable on a large rocket.