Raptor Engine

Raptor 2 Engines at Starbase in April 2022. They produce 230 tons of force each.

**Raptor** is a family of full-flow staged-combustion-cycle rocket engines developed and manufactured by SpaceX for use on the in-development SpaceX Starship. The engine is powered by cryogenic liquid methane and liquid oxygen ("methalox") rather than the RP-1 and liquid oxygen ("kerolox") used in SpaceX's prior Merlin and Kestrel rocket engines. The Raptor engine has more than twice the thrust of SpaceX's Merlin 1D engine that powers the Falcon 9 and Falcon Heavy launch vehicles.

Raptor is used in the Starship system in both the super-heavy-lift Super Heavy booster and in the Starship spacecraft which acts as the second stage when launched from Earth and as an independent spacecraft in LEO and beyond. Starship is planned to be used in various applications, including Earth-orbit satellite delivery, deployment of a large portion of SpaceX's Starlink satellite constellation, exploration, Moon landing, and colonization of Mars.

The inner engines can gimbal; Elon Musk shared a video of a test on Booster 4:

According to Musk, Raptor 1 engines produce 185 metric tons of force and the Raptor 2 engines, which started production in November or December 2021, "will do 230+ tons or over half a million pounds of force".

A simple, yet in-depth explanation of the engine can be found on Everyday Astronaut's site, including a comprehensive video. Furthermore, his interview with Elon Musk on the Raptor 2 version is also much recommended.

## Variants

### Raptor Vacuum (RVAC):

Raptor Vacuum (RVac) is a variant of Raptor with an extended, regeneratively-cooled nozzle for higher specific impulse in the vacuum of space. The vacuum-optimized Raptor engine is aiming for a specific impulse of ~380 s (3,700 m/s). A full-duration test of version 1 of the Raptor Vacuum engine was completed in September 2020 at the SpaceX development facility in McGregor, Texas. The first three operational Raptor Vacuum engines were slated to fly on SpaceX's first orbital Starship prototype, Ship 20 (S20), and were installed on 4 August 2021. However, Ship 20 was retired before it flew. The first in-flight ignition of an RVac was on Ship 25 (S25) during the Starship Flight Test 2.

### Raptor (Sea Level)

The Raptor engine is powered by subcooled liquid methane, and subcooled liquid oxygen in a full-flow staged combustion cycle. This is a departure from the simpler "open-cycle" gas generator system and LOX/kerosene propellants that the current Merlin engines use. Also, the RS-25 engines (which were first used on the Space Shuttle) use a simpler form of a staged combustion cycle, as do several Russian rocket engines, including the RD-180 and the RD-191. This design allows the engine to achieve greater efficiency by using all of the available fuel without wasting any of it to power its turbo pumps. An oxygen-rich turbine will power an oxygen turbopump, and fuel-rich turbine will power a methane turbopump. Both streams—oxidizer and fuel—will be mixed completely in the gas phase before they enter the combustion chamber.

## References

1. ↑ https://www.nasaspaceflight.com/2022/01/raptor-2-starbase-update/
2. ↑ https://web.archive.org/web/20200402122214/https://www.spacex.com/sites/spacex/files/starship\_users\_guide\_v1.pdf
3. ↑ https://archive.today/20131025232611/http://www.spacenews.com/article/launch-report/37859spacex-could-begin-testing-methane-fueled-engine-at-stennis-next-year
4. ↑ https://twitter.com/elonmusk/status/1472052839316963329
5. ↑ https://twitter.com/elonmusk/status/1472054278613254147
6. ↑ https://everydayastronaut.com/raptor-engine/
7. ↑ https://www.youtube.com/watch?v=E7MQb9Y4FAE

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