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Raptor is the first member of a family of cryogenic〔https://www.youtube.com/watch?v=hJD0MMP4nkM〕 methane-fueled rocket engines under development by SpaceX. It is specifically intended to power high performance lower and upper stages for SpaceX super-heavy launch vehicles. The engine will be powered by liquid methane〔http://spaceref.com/news/viewsr.html?pid=47400〕 and liquid oxygen (LOX),〔 rather than the RP-1 kerosene and LOX used in all previous Falcon 9 rockets, which use Merlin 1C & D engines. Earlier concepts for Raptor would have used liquid hydrogen (LH2) fuel rather than methane. The Raptor engine will have over six times the thrust of the Merlin 1D vacuum engine that powers the second stage of the current Falcon 9, the Falcon 9 v1.1. The broader Raptor concept "is a highly reusable methane staged-combustion engine that will power the next generation of SpaceX launch vehicles designed for the exploration and colonization of Mars."〔 According to Elon Musk, this design will be able to achieve full reusability (all rocket stages), and as a result, "a two order of magnitude reduction in the cost of spaceflight".〔https://www.youtube.com/watch?v=hJD0MMP4nkM〕 ==History== ''Raptor'' was first publicly discussed by SpaceX's Max Vozoff at the American Institute of Aeronautics and Astronautics Commercial Crew/Cargo symposium in 2009.〔 , SpaceX had a small number of staff working on the Raptor upper-stage engine, then still a LH2/LOX concept, at a low level of priority. Further mention of the development program occurred in 2011. In March 2012, news accounts asserted that the Raptor upper-stage engine development program was underway, but that details were not being publicly released.〔 〕 In October 2012, SpaceX publicly announced concept work on a rocket engine that would be "several times as powerful as the Merlin 1 series of engines, and won't use Merlin's RP-1 fuel", but declined to specify the specific fuel to be used.〔 〕 They indicated that details would be forthcoming in "one to three years" and that the large engine was intended for a new SpaceX rocket, using multiple of these large engines, that would notionally launch payload masses of the order of to low Earth orbit, exceeding the payload mass capability of the NASA Space Launch System.〔 This was cleared up the next month when, in November 2012, CEO Elon Musk announced a new direction for the propulsion division of SpaceX: developing methane-fueled rocket engines.〔 〕 He further indicated that the engine concept that had been codenamed Raptor would now become a methane-based design,〔 and that methane would be the fuel of choice for SpaceX' plans for Mars colonization.〔 Because of the presence of water underground and carbon dioxide in the atmosphere of Mars, methane, a simple hydrocarbon, can easily be synthesized on Mars using the Sabatier reaction. In-situ resource production on Mars has been examined by NASA and found to be viable for oxygen, water, and methane production. According to a study published by the Chicago School of Mines, in-situ resource utilization such as methane from Mars makes space missions more feasible technically and economically and enables reusability. Methane has been discovered in meteorites from Mars.〔http://phys.org/news/2015-06-scientists-methane-mars-meteorites.html〕 When first mentioned by SpaceX in 2009, the term "Raptor" was applied exclusively to an upper-stage engine concept〔 〕—and 2012 pronouncements indicate that it still was a concept for an upper stage engine〔 〕—but in early 2014 SpaceX confirmed that Raptor would be used both on a new second stage, as well as for the large (nominally, 10-meter-diameter) core of the Mars Colonial Transporter. Each booster core will utilize nine Raptor engines, similar to the use of nine Merlin 1s on each Falcon 9 booster core.〔 Early hints that a staged-combustion methane engine was under consideration at SpaceX were given in May 2011 when SpaceX asked if the Air Force was interested in a methane-fueled engine as an option to compete with the mainline kerosene-fueled engine that had been requested in the USAF ''Reusable Booster System High Thrust Main Engine'' solicitation.〔 Public information released in November 2012 indicated that SpaceX may have a family of Raptor-designated rocket engines in mind;〔 〕 this was confirmed by SpaceX in October 2013.〔 However, SpaceX COO Gwynne Shotwell clarified in March 2014 that the focus of the new engine development program is exclusively on the full-size Raptor engine; smaller subscale methalox engines are not planned on the development path to the very large Raptor engine.〔 〕 In October 2013, SpaceX announced that they would be performing methane engine tests of the Raptor engine at the John C. Stennis Space Center in Hancock County, Mississippi, and that SpaceX would add equipment to the existing test stand infrastructure in order to support liquid methane engine testing.〔 〕 In April 2014, SpaceX completed the requisite upgrades and maintenance to the Stennis test stand to prepare for testing of Raptor components, and expects to begin tests at the facility prior to the end of May 2014.〔 〕 October 2013 was the first time SpaceX disclosed a nominal design thrust of the Raptor engine—〔 〕—although early in 2014 they announced a Raptor engine with greater thrust, and in 2015, one with lower thrust that might better optimize thrust-to-weight. In February 2014, Tom Mueller, the head of rocket engine development at SpaceX, revealed in a speech that Raptor was being designed for use on a vehicle where nine engines would "put over 100 tons of cargo up to Mars," and that the rocket would be more powerful than previously released publicly, producing greater than .〔〔 〕 A June 2014 talk by Mueller provided more specific engine performance target specifications indicating of sea-level thrust, of vacuum thrust, and a specific impulse of for a vacuum version. Earlier information had estimated the design Isp under vacuum conditions as only 363 s.〔 In January 2015, Elon Musk made a statement that the thrust they were currently targeting was around , much lower than older comments mentioned. This brought into question much of the speculation surrounding a 9-engine booster, as he stated "there will be a lot of ()"〔Musk, E. (January 6, 2015) ("Thrust to weight is optimizing for a surprisingly low thrust level, even when accounting for the added mass of plumbing and structure for many engines. Looks like a little over 230 metric tons (~500 klbf) of thrust per engine, but we will have a lot of them :)" ) ''Reddit.com''〕 By August 2015, an Elon Musk statement surfaced that indicated the oxidizer to fuel ratio of the Mars-bound engine would be approximately 3.8 to 1.〔(How (and Why) SpaceX Will Colonize Mars ), accessed 19 Augus7 2015. Musk: "''The critical elements of the solution are rocket reusability and low cost propellant (CH4 and O2 at an O/F ratio of ~3.8). And, of course, making the return propellant on Mars, which has a handy CO2 atmosphere and lots of H2O frozen in the soil.''"〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Raptor (rocket engine)」の詳細全文を読む スポンサード リンク
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