(left) compared to a sea-level Raptor 1 engine (right)
Conception SpaceX's
Merlin and
Kestrel rocket engines use a
RP-1 and liquid oxygen ("kerolox") combination. Raptor has about triple the thrust of SpaceX's
Merlin 1D engine, which powers the
Falcon 9 and
Falcon Heavy launch vehicles. Raptor was conceived to burn
hydrogen and
oxygen propellants as of 2009. SpaceX had a few staff working on the Raptor upper-stage engine at a low priority in 2011. In October 2012, SpaceX announced concept work on an engine that would be "several times as powerful as the
Merlin 1 series of engines, and won't use Merlin's
RP-1 fuel".
Development In November 2012, Musk announced that SpaceX was working on
methane-fueled rocket engines, that Raptor would be methane-based, and that methane would fuel Mars colonization. Because of the presence of
underground water and
carbon dioxide in
Mars atmosphere, methane, a simple
hydrocarbon, could be synthesized on Mars using the
Sabatier reaction.
NASA analysis found
in-situ resource production on Mars to be viable for oxygen, water, and methane production. In early 2014 SpaceX confirmed that Raptor would be used for both first and second stages of its next rocket. This held as the design evolved from the
Mars Colonial Transporter the
Big Falcon Rocket, and ultimately, Starship. The concept evolved from a family of Raptor-designated rocket engines (2012) to focus on the full-size Raptor engine (2014). In January 2016, the US Air Force awarded a development contract to SpaceX to develop a prototype Raptor for use on the
upper stage of
Falcon 9 and
Falcon Heavy. The first version was intended to operate at a chamber pressure of . As of July 2022, chamber pressure had reached 300 bars in a test. and said SpaceX would aim to ultimately achieve over 330 tonnes of thrust on the sea-level booster engines. Raptor 1 and 2 engines require a heat shroud to protect pipes and wiring from the heat of high-velocity atmospheric re-entry,
Testing at
Stennis Space Center in 2015 Initial
development testing of Raptor components was done at NASA's
Stennis Space Center, beginning in April 2014. Testing focused on startup and shutdown procedures, as well as hardware characterization and
verification. The engine had thrust. It was the first-ever full-flow staged combustion methalox engine to reach a test stand. SpaceX completed many static fire tests on a vehicle using Raptor 2s, including a 31 engine test (intended to be 33) on 9 February 2023, and a 33 engine test on 25 August 2023. During testing, more than 50 chambers melted, and more than 20 engines exploded. SpaceX completed its
first integrated flight test of Starship on 20 April 2023. The rocket had 33 Raptor 2 engines, but three of those were shut down before the rocket lifted off from the launch mount. The flight test was terminated after climbing to an altitude of ~39 km over the Gulf of Mexico. Multiple engines were out before the flight termination system (FTS) destroyed the booster and ship. On the
second integrated flight test, all 33 booster engines remained lit until boostback burn startup, and all six Starship engines remained lit until the FTS was activated. On the booster's landing burn, only 3 engines of the planned 13 lit, with 2 shutting down rapidly, the other remained lit until the booster was destroyed ~462 metres above sea level. which was successfully flown during Super Heavy Booster 14's ascent burn and was recovered after its successful catch by the launch tower. A further 29 raptors were reflown on B14 for Starship's
ninth test flight.
Starship Original configuration during ascent (artist's concept) In November 2016, Raptor was projected to power the proposed
Interplanetary Transport System (ITS), in the early 2020s. In September 2017 Musk said that a smaller Raptor engine—with slightly over half as much thrust as the previous designs—would be used on the next-generation rocket, a -diameter launch vehicle termed Big Falcon Rocket (BFR) and later renamed
Starship. The redesign was aimed at Earth-orbit and
cislunar missions so that the new system might
pay for itself, in part, through economic spaceflight activities in the near-Earth space zone. With the much smaller launch vehicle, fewer Raptor engines would be needed. BFR was then slated to have 31 Raptors on the first stage and 6 on the second stage. has its tiles inspected
Proposed Falcon 9 upper stage In January 2016, the
United States Air Force (USAF) awarded a development contract to SpaceX to develop a Raptor prototype for use on the
upper stage of the
Falcon 9 and
Falcon Heavy. The contract required double-matching funding by SpaceX of at least . Engine testing was planned for NASA's
Stennis Space Center in
Mississippi under US Air Force supervision. It was to use
liquid methane and
liquid oxygen propellants, a
full-flow staged combustion cycle, and be reusable. In 2019 the (marginal) cost of the engine was stated to be approaching . SpaceX planned to mass-produce up to 500 Raptor engines per year, each costing less than . == Versions ==