View source for J-2X

{{Short description|Liquid-fueled rocket engine}}
{{Infobox rocket engine
|name            = J-2X
|image           = J-2X.jpg
|image_size      = 200px
|caption         = A computer rendering of a J-2X.
|country_of_origin= United States
|date            =
|first_date      =
|last_date       =
|designer        =
|manufacturer    = [[Aerojet Rocketdyne]]
|purpose         = [[Upper stage]] engine
|associated      = Block II [[Space Launch System]] ([[Earth Departure Stage|EDS]])
|predecessor     = [[J-2 (rocket engine)|J-2]]
|successor       =
|status          = Unknown

|type            = liquid
|oxidiser        = [[Liquid oxygen]]
|fuel            = [[liquid hydrogen]]
|mixture_ratio   = 5.5–4.5
|cycle           = [[Gas-generator cycle (rocket)|Gas generator]]
|pumps           =
|description     =
|combustion_chamber=
|nozzle_ratio    = 92:1

|thrust          =
|thrust_at_altitude=
|thrust(Vac)     = {{Convert|1307|kN|sigfig=3|abbr=on}}
|thrust(SL)      =
|thrust_to_weight= 55.04
|chamber_pressure=
|specific_impulse=
|specific_impulse_vacuum= {{convert|448|isp}}
|specific_impulse_sea_level=
|total_impulse   =
|burn_time       =
|capacity        =
|dimensions      =
|length          = {{Convert|4.7|m}}
|diameter        = {{Convert|3|m}}
|dry_weight      = {{Convert|5450|lb}}

|references      =<ref name="PWRJ-2X">{{cite web|url=http://www.rocket.com/j-2x-engine-0|title=J-2X Engine|publisher=Aerojet Rocketdyne|accessdate=9 January 2014|url-status=dead|archiveurl=https://web.archive.org/web/20140112120038/http://www.rocket.com/j-2x-engine-0|archivedate=12 January 2014}}</ref><ref name="EAJ-2X">{{Cite web|title=J-2X |url=http://www.astronautix.com/engines/j2x.htm |publisher=Encyclopedia Astronautica |author=Mark Wade |date=17 November 2011 |url-status=dead |archiveurl=https://web.archive.org/web/20111212045512/http://www.astronautix.com/engines/j2x.htm |archivedate=12 December 2011 }}</ref>
|notes           =
}}
The '''J-2X''' is a [[liquid-fuel rocket|liquid-fueled]] [[cryogenic rocket engine]] that was planned for use on the Ares rockets of [[NASA]]'s [[Constellation program]], and later the [[Space Launch System]]. Built in the United States by [[Aerojet Rocketdyne]] (formerly, [[Pratt & Whitney Rocketdyne]]), the J-2X burns [[Cryogenic fuel|cryogenic]] [[liquid hydrogen]] and [[liquid oxygen]] propellants, with each engine producing {{Convert|1307|kN|sigfig=3|abbr=on}} of [[thrust]] in vacuum at a [[specific impulse]] (''I''<sub>sp</sub>) of {{convert|448|isp}}.<ref name="EAJ-2X"/> The engine's mass is approximately 2,470&nbsp;kg (5,450 Lb), significantly heavier than its predecessors.<ref name="EAJ-2X"/>

The J-2X was intended to be based on the [[J-2 (rocket engine)|J-2]] used on the [[S-II]] and [[S-IVB]] stages of the [[Saturn (rocket family)|Saturn]] rockets used during the [[Apollo program]], but as required thrust for the Ares I increased due to weight problems it became a clean-sheet design.  It entered development in 2007 as part of the now-cancelled [[Constellation program]].<ref name="EAJ-2X"/> Originally planned for use on the [[upper stage]]s of the [[Ares I]] and [[Ares V]] rockets, the J-2X was later intended for use in the [[Earth Departure Stage]] of the Block 2 [[Space Launch System]], the successor to the Constellation program. The engine is intended to be more efficient and simpler to build than its J-2 ancestor, and cost less than the [[RS-25]] engine.<ref name="PWRJ-2X"/> Differences in the new engine include the removal of [[beryllium]], a centrifugal turbo pump versus the axial turbo pump of the J-2, different chamber and nozzle expansion ratios, a channel-walled combustion chamber versus the tube-welded chamber of the J-2, a redesign of all the electronics, a [[gas generator]] and supersonic main injector based on the [[RS-68]],<ref>{{cite web |url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20100034922_2010034367.pdf |title=The J-2X Upper Stage Engine: From Design to Hardware. Thomas Byrd, Deputy Manager, J-2X Upper Stage Engine Element Ares Projects Office Marshall Space Flight Center Huntsville, AL 35812}}</ref> and the use of 21st-century joining techniques.<ref name="EAJ-2X"/><ref>{{cite web|date=4 June 2012|title=J-2X Extra: What's in a Name?|url=http://blogs.nasa.gov/cm/newui/blog/viewpostlist.jsp?blogname=J2X|publisher=NASA|author=William D Greene|access-date=11 June 2012|archive-url=https://web.archive.org/web/20101109091510/http://blogs.nasa.gov/cm/newui/blog/viewpostlist.jsp?blogname=J2X|archive-date=9 November 2010|url-status=dead}}</ref>

==Testing==
On 16 July 2007 NASA officially announced the award to [[Pratt & Whitney Rocketdyne]] (PWR) of a $1.2 billion contract "for design, development, testing and evaluation of the J-2X engine",<ref>{{cite web|title=NASA Awards Upper Stage Engine Contract for Ares Rockets|publisher=NASA|date=16 July 2007|url=http://www.nasa.gov/home/hqnews/2007/jul/HQ_C07030_J2X_Contract_prt.htm|accessdate=17 July 2007|archive-date=1 August 2020|archive-url=https://web.archive.org/web/20200801040403/https://www.nasa.gov/home/hqnews/2007/jul/HQ_C07030_J2X_Contract_prt.htm|url-status=dead}}</ref> and began construction of a new test stand for altitude testing of J-2X engines at [[John C. Stennis Space Center|Stennis Space Center]] on 23 August 2007.<ref>{{cite web|date=23 August 2007|title=NASA's Stennis Space Center Marks New Chapter in Space Exploration|url=http://www.nasa.gov/home/hqnews/2007/aug/HQ_07180_Stennis_groundbreaking.html|publisher=NASA|access-date=26 February 2012|archive-date=4 April 2012|archive-url=https://web.archive.org/web/20120404062335/http://www.nasa.gov/home/hqnews/2007/aug/HQ_07180_Stennis_groundbreaking.html|url-status=dead}}</ref>

Component testing was undertaken between December 2007 and May 2008, with nine tests of heritage J-2 engine components at SSC in preparation for the design of the J-2X engine.<ref>{{cite web|title=NASA Successfully Completes First Series of Ares Engine Tests|url=http://www.nasa.gov/home/hqnews/2008/may/HQ_08116_power_pack_tests.html|publisher=NASA|date=8 May 2008|access-date=26 February 2012|archive-date=6 April 2012|archive-url=https://web.archive.org/web/20120406031143/http://www.nasa.gov/home/hqnews/2008/may/HQ_08116_power_pack_tests.html|url-status=dead}}</ref> and on 8 September 2008 PWR announced successful testing of the initial J-2X gas generator design.<ref>{{cite web|url=http://www.pw.utc.com/Media+Center/Press+Releases/Pratt+%26+Whitney+Rocketdyne+Completes+Successful+Test+of+J-2X+Gas+Generator|title=Pratt & Whitney Rocketdyne Completes Successful Test of J-2X Gas Generator|date=8 September 2008|publisher=Pratt & Whitney Rocketdyne|url-status=dead|archiveurl=https://web.archive.org/web/20090809174743/http://www.pw.utc.com/Media+Center/Press+Releases/Pratt+%26+Whitney+Rocketdyne+Completes+Successful+Test+of+J-2X+Gas+Generator|archivedate=9 August 2009}}</ref> The completion of a second round of successful gas generator tests was announced on 21 September 2010.<ref>{{cite press release|title=Pratt & Whitney Rocketdyne Completes Latest Round of Tests on J-2X Gas Generator|url=https://www.prnewswire.com/news-releases/pratt--whitney-rocketdyne-completes-latest-round-of-tests-on-j-2x-gas-generator-103466979.html|publisher=Pratt & Whitney Rocketdyne|date=September 21, 2010|access-date=December 10, 2022}}</ref>

Starting in 2011, the full J-2X engine, derived from heritage and new designs, has undergone hot-fire tests.
* June 2011: The first hot-fire test.<ref>{{cite magazine |last=Morring|first=Frank|title=First J-2X Hot-Fire Test Could Come Next Week|url=https://aviationweek.com/first-j-2x-hot-fire-test-could-come-next-week |accessdate=19 June 2011|magazine=[[Aviation Week & Space Technology|Aviation Week]] |archive-url=https://web.archive.org/web/20201028105144/https://aviationweek.com/first-j-2x-hot-fire-test-could-come-next-week |archive-date=28 October 2020 |url-status=live |url-access=subscription }}</ref>
* November 2011: A test-firing lasting 499.97&nbsp;seconds.<ref>{{cite web|title=NASA Test Fires Engine for Giant New Rocket|url=http://www.space.com/13567-nasa-giant-rocket-engine-test-j2x.html|date=9 November 2011|accessdate=26 February 2012|publisher=Space.com}}</ref>
* June 2012: A test-firing lasting 1,150 seconds, during which the J-2X was throttled up and down.<ref>{{cite web|title=NASA Surpasses Test Facility Record with J-2X Powerpack Test|url=http://www.nasa.gov/home/hqnews/2012/jun/HQ_12-167_J-2X_Testing_Record.html|date=8 June 2012|accessdate=10 June 2012|publisher=National Aeronautics and Space Administration}}</ref>
* July 2012: A test-firing for 1,350 seconds ({{frac|22|1|2}} minutes).<ref>{{cite web|title=A Summer of Records for Engine Testing|url=http://www.nasa.gov/exploration/systems/sls/j2x/pp_july24_1.html|date=26 June 2012|accessdate=26 June 2012|publisher=National Aeronautics and Space Administration}}</ref>
* December 2012: Final test-firing of the [[Powerpack (rocket engine)|powerpack]] assembly.<ref>{{cite web|title=Beating Heart of J-2X Engine Finishes Year of Successful Testing|url=http://www.nasa.gov/exploration/systems/sls/j2x/j2x_powerpack_dec13.html|date=13 Dec 2012|accessdate=14 Dec 2012|publisher=National Aeronautics and Space Administration|archive-date=17 December 2012|archive-url=https://web.archive.org/web/20121217033230/http://www.nasa.gov/exploration/systems/sls/j2x/j2x_powerpack_dec13.html|url-status=dead}}</ref>
*Feb 2013: Testing of engine 10002 begins on test stand A2 for 6 tests.<ref>{{cite web|title=NASA Set for New Round Of J-2X Testing at Stennis Space Center|url=http://www.nasa.gov/home/hqnews/2013/feb/HQ_13-047_New_J-2X_Testing.html#.UvONEnmIK-Q|date=11 Feb 2013|accessdate=6 Feb 2014|publisher=National Aeronautics and Space Administration}}</ref>
*June 2013: Engine 10002 moved to test stand A1 for 7 further tests.<ref name="blogs.nasa.gov">{{cite web|title=J-2X Progress: November 2013 Update|url=http://blogs.nasa.gov/J2X/2013/11/15/j-2x-progress-november-2013-update/|date=15 Nov 2013|accessdate=6 Feb 2014|publisher=National Aeronautics and Space Administration}}</ref>
*Sept 2013: Final test-firing of engine 10002.<ref>{{cite web|title=One Final Test for J-2X Engine No. 10002|url=https://www.youtube.com/watch?v=LAEXMyiijfg |archive-url=https://ghostarchive.org/varchive/youtube/20211221/LAEXMyiijfg |archive-date=2021-12-21 |url-status=live|date=5 Sep 2013|accessdate=6 Feb 2014|publisher=National Aeronautics and Space Administration}}{{cbignore}}</ref>
*Nov 2013: Testing of engine 10003 begins.<ref name="blogs.nasa.gov"/>
<gallery mode=packed>
Image:J-2X concept image June 2006.png|Concept image of the J-2X engine.
Image:Test of the J-2X Engine.JPG|Test of the J-2X engine 'workhorse' gas generator.
Image:NASA's J-2X Engine.jpg|Cold Flow nozzle testing for the J2X program.
Image:J2-X Engine NASA test - 592563main SSC-2011-01852 946-710.jpg|The J-2X being tested at NASA's [[John C. Stennis Space Center]] in [[Hancock County, Mississippi]].
</gallery>

==Program status==
In October 2013, it was reported that work on the J-2X would pause following development testing in 2014, due to funding limitations, an expected delayed need for the engine's capabilities for piloted missions to Mars, and selection<ref>{{cite web|last1=Bergin|first1=Chris|title=NASA lines up Exploration Upper Stage workhorse for SLS|url=http://www.nasaspaceflight.com/2014/10/nasa-exploration-upper-stage-workhorse-sls/|website=NASASpaceflight.com|date=12 October 2014|accessdate=November 8, 2014}}</ref> of the [[RL10]] powered [[Exploration Upper Stage]] for SLS.<ref>{{cite web|title=NASA's J-2X Engine To Be Mothballed After Testing|url=http://www.aviationweek.com/Article.aspx?id=/article-xml/asd_10_04_2013_p01-01-623762.xml|date=4 Oct 2013|accessdate=29 Oct 2013|publisher=Aviation Week and Space Technology magazine|archive-date=2 November 2013|archive-url=https://web.archive.org/web/20131102160656/http://www.aviationweek.com/Article.aspx?id=/article-xml/asd_10_04_2013_p01-01-623762.xml|url-status=dead}}</ref>

In September 2022, the components of the J-2X were put up for auction on GSA Auctions, likely confirming the cancellation of the program.<ref>{{cite web|title=GROUP 1 COMPONENTS TO ASSEMBLE J2X ROCKET ENGINE|url=https://gsaauctions.gov/gsaauctions/aucdsclnk?sl=41QSCI22160001|accessdate=September 12, 2022}}</ref>

==See also==
* [[HG-3 (rocket engine)|HG-3 engine]]
* [[M-1 (rocket engine)]]

==References==
{{Commons category|J-2X (rocket engine)}}
{{Reflist}}

{{J-2 (rocket engine)}}
{{Rocket engines}}

{{Project Constellation}}

[[Category:Rocket engines using hydrogen propellant]]
[[Category:Rocketdyne engines]]
[[Category:Space Launch System]]
[[Category:Rocket engines using the gas-generator cycle]]
[[Category:Rocket engines of the United States]]