Editing SpaceX Merlin (section)

== Past engine concepts ==
===Merlin 2 concept===
At the [[American Institute of Aeronautics and Astronautics]] Joint Propulsion conference on July 30, 2010, SpaceX McGregor rocket development facility director [[Tom Markusic]] shared some information from the initial stages of planning for a new engine. SpaceX’s Merlin 2 [[LOX]]/RP-1-fueled engine on a [[gas-generator cycle]], capable of a projected {{convert|1700000|lbf|kN|abbr=on|order=flip}} of thrust at sea level and {{convert|1920000|lbf|kN|abbr=on|order=flip}} in a vacuum and would provide the power for conceptual super-heavy-lift launch vehicles from SpaceX, which Markusic dubbed [[Falcon X]] and [[Falcon XX]]. Such a capability, if built, would have resulted in an engine with more thrust than the [[Rocketdyne F-1|F-1 engines]] used on the [[Saturn V]].<ref>{{cite web |url=http://hobbyspace.com/nucleus/index.php?itemid=22430 |title=SpaceX Merlin 2 engine, heavy lift designs |website=Hobbyspace.com |date=July 30, 2010 |archiveurl=https://web.archive.org/web/20111013051925/http://hobbyspace.com/nucleus/index.php?itemid=22430 |archivedate=October 13, 2011 |url-status=dead}}</ref>

Conceived to be potentially used on more capable variants of the Falcon 9 Heavy, Markusic indicated that the Merlin 2 "could be qualified in three years for $1 billion".<ref name=aw20100805>{{cite news |url=http://www.aviationweek.com/aw/generic/story_channel.jsp?channel=space&id=news/asd/2010/08/05/07.xml&headline=SpaceX%20Unveils%20Heavy-Lift%20Vehicle%20Plan |title=SpaceX Unveils Heavy-Lift Vehicle Plan |work=[[Aviation Week & Space Technology]] |first=Guy |last=Norris |date=August 5, 2010 |archiveurl=https://web.archive.org/web/20100821051110/http://www.aviationweek.com/aw/generic/story_channel.jsp?channel=space&id=news/asd/2010/08/05/07.xml&headline=SpaceX%20Unveils%20Heavy-Lift%20Vehicle%20Plan |archivedate=August 21, 2010}}</ref> By mid-August, SpaceX CEO [[Elon Musk]] clarified that while the Merlin 2 engine architecture was a key element of any effort SpaceX would make toward their objective of "super-heavy lift" launch vehicles—and that SpaceX did indeed want to "move toward super heavy lift"—the specific potential design configurations of the particular launch vehicles shown by Markusic at the propulsion conference were merely conceptual "brainstorming ideas", just a "bunch of ideas for discussion."<ref name=aw20100811>{{cite news |url=http://www.aviationweek.com/aw/generic/story_channel.jspchannel=space&id=news/asd/2010/08/11/07.xml&headline=Musk%20Clarifies%20SpaceX%20Position%20On%20 |title=Exploration Musk Clarifies SpaceX Position On Exploration |work=[[Aviation Week & Space Technology]] |date=August 11, 2010 |accessdate=August 16, 2010 }} {{subscription required}}</ref>

Since the original discussion, no work on any "Merlin 2" [[kerolox]]<!-- RP-1 and LOX --> engine has been pursued and made public. At the 2011 Joint Propulsion Conference, Elon Musk stated that SpaceX were instead working towards a potential [[Staged combustion cycle|staged cycle engine]].<ref name="Musk & Shotwell">{{cite web |url=http://www.hobbyspace.com/nucleus/index.php?itemid=31359 |title=Webcasts of Elon Musk & Gwynne Shotwell at AIAA mtg |website=Hobbyspace.com |date=August 1, 2011 |archiveurl=https://web.archive.org/web/20111102183102/http://www.hobbyspace.com/nucleus/index.php?itemid=31359 |archivedate=November 2, 2011 |url-status=dead}}</ref> 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".<ref name=fg20121017>{{cite news |url=https://www.flightglobal.com/news/articles/spacex-aims-big-with-massive-new-rocket-377687/ |title=SpaceX aims big with massive new rocket |work=[[Flightglobal]] |last=Rosenberg |first=Zach |date=October 15, 2012 |accessdate=October 17, 2012}}</ref> They indicated that the large engine was intended for a new SpaceX rocket, using multiple of these large engines could notionally launch payload masses of the order of {{convert|150|to|200|tonne|ST|lk=on}} to [[low-Earth orbit]]. The forthcoming engine currently under development by SpaceX has been named "[[Raptor (rocket engine)|Raptor]]". Raptor will use [[liquid methane]] as a fuel, and was stated as having a sea-level thrust of {{convert|1500000|lbf|kN|order=flip}}.<ref name=pbt20140219>{{cite news |url=http://www.pacbiztimes.com/2014/02/19/spacexs-propulsion-chief-elevates-crowd-in-santa-barbara/ |title=SpaceX propulsion chief elevates crowd in Santa Barbara |work=Pacific Business Times |first=Stephen |last=Nellis |date=February 19, 2014 |accessdate=February 22, 2014}}</ref> Since the initial announcement of Raptor, Musk has updated the specification to approximately {{convert|230|tonne-force|kN lbf|abbr=out}}—about one-third the original published figure—based on the results of optimizing for thrust-to-weight ratio.<ref name="reddit20150106">{{cite web |url=http://www.reddit.com/r/IAmA/comments/2rgsan/i_am_elon_musk_ceocto_of_a_rocket_company_ama/cnfpuwi |title=I am Elon Musk, CEO/CTO of a rocket company, AMA! |website=Reddit.com |first=Elon |last=Musk |date=January 6, 2015 |accessdate=January 30, 2016 |quote=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 :)}}</ref>