View source for Engineering:Earth Departure Stage

{{Infobox rocket stage
<!----Image (optional)---->
|image   =
|imsize  =  270
|caption =  An Ares V EDS with an [[Engineering:Altair (spacecraft)|Altair]] lunar lander and [[Engineering:Orion (spacecraft)|Orion]].
<!----Core parameters (required)---->
|name           =  Earth Departure Stage
|manufacturer   =  <!--Manufacturer, required-->
|country-origin = United States
<!----Associated rockets (optional)---->
|rockets     = Ares V<br/>[[Astronomy:Space Launch System|SLS]] Block 2
|derivatives =  <!--derived rockets, optional-->
|comparable  = [[Astronomy:S-IVB|S-IVB]]
<!----Launch history (required)---->
|status   =  Cancelled (Ares V)<br/>Postponed ([[Astronomy:Space Launch System|SLS]])
|launches =  <!--total launches to date, optional-->
|success  =  <!--total successful launches, optional-->
|fail     =  <!--total failed launches, optional-->
|other_outcome =  <!--number of launches with unknown outcomes (or in progress), optional-->
|first    =  <!--date of maiden flight, optional-->
|last     =  <!--date of final flight, optional-->
<!--Stages/boosters (optional)-->
|stagedata    =  <!--insert one of the following templates for each stage:-->
  {{Infobox rocket/Stage
  |name       = Ares V EDS
  |length     =  {{Convert|30|m}}<!--length of a single booster/stage in metres, optional, use {{convert}}-->
  |diameter   =  {{Convert|10|m}}<!--diameter of a single booster/stage, optional in metres, use {{convert}}-->
  |empty      =  {{Convert|47400|kg}}<!--empty mass of a single booster/stage in kilograms, optional, use {{convert}}-->
  |gross      =  {{Convert|294000|kg}}
  |engines    =  1 or 2 J-2X
  |thrust     =  {{Convert|1310|kN}}
  |SI         =  {{cvt|448|isp}} (vacuum)
  |burntime   =  <!--burn time, required-->
  |fuel       = [[Chemistry:Liquid hydrogen|LH<sub>2</sub>]]/[[Physics:Liquid oxygen|LOX]]
  }}
  {{Infobox rocket/Stage
  |name    = [[Astronomy:Space Launch System|SLS]] Block II EDS
  |length     =  {{Convert|24|m}}
  |diameter   =  <!--diameter of a single booster/stage, optional in metres, use {{convert}}-->
  |empty      =  <!--empty mass of a single booster/stage in kilograms, optional, use {{convert}}-->
  |gross      =  <!--gross (fuelled) mass of a single booster/stage, optional--> 
  |engines    =  1 or 2 J-2X
  |thrust     =  {{Convert|1310|kN}}
  |SI         =  {{cvt|448|isp}} (vacuum)
  |burntime   =  <!--burn time, required-->
  |fuel       = [[Chemistry:Liquid hydrogen|LH<sub>2</sub>]]/[[Physics:Liquid oxygen|LOX]]
  }}
}}
The '''Earth Departure Stage''' ('''EDS''') is the name given to the proposed second [[Astronomy:Multistage rocket|stage]] of the Block 2 [[Astronomy:Space Launch System|Space Launch System]]. The EDS is intended to boost the rocket's payload into a [[Astronomy:Parking orbit|parking orbit]] around the Earth and from there send the payload out of [[Astronomy:Low Earth orbit|low Earth orbit]] to its destination in a manner similar to that of the [[Astronomy:S-IVB|S-IVB]] rocket stage used on the [[Engineering:Saturn V|Saturn V]] rockets that propelled the Apollo spacecraft to the Moon. Its development has been put on hold (though not abandoned) until stages capable of transferring heavy payloads to Mars are required (currently expected in the 2030s).

==Ares V==

===Design===
The EDS used on the cancelled Ares V would have been propelled by a single J-2X main engine fuelled with [[Physics:Liquid oxygen|liquid oxygen]] (LOX) and [[Chemistry:Liquid hydrogen|liquid hydrogen]] (LH<sub>2</sub>), and was to have been designed at [[Organization:NASA|NASA]]'s [[Organization:Marshall Space Flight Center|Marshall Space Flight Center]] in Huntsville, Alabama as part of Project Constellation. Originally, the stage would have been based on the [[Engineering:Space Shuttle|Space Shuttle]]'s [[Engineering:Space Shuttle external tank|external tank]], and would have used two J-2X engines, while the Ares V core booster would have used five [[Engineering:RS-25|RS-25]] engines and two [[Engineering:Space Shuttle Solid Rocket Booster|5-segment Solid Rocket Boosters]] during the first eight minutes of flight. When the Ares V was then redesigned around the use of five (later six<ref>[http://www.space.com/news/ap-080625-nasa-aresv-beefed-up.html SPACE.com - NASA Beefs up Next-Generation Moon Rocket<!-- Bot generated title -->]</ref>) RS-68B rocket engines used on the [[Engineering:Delta IV Heavy|Delta IV Heavy]] as of 2019, the EDS was then redesigned using only a single J-2X engine and a common bulkhead, thus in its final design, the EDS resembled an oversized S-IVB, but with the capability of on-site storage (using new propellant storage techniques along with a "loiter skirt" containing solar panels for electricity) for up to 4 days, something impossible with the old S-IVB.

===Mission===
Launched on the Ares V rocket, the EDS with its [[Engineering:Altair (spacecraft)|Altair]] payload would not have become active until the six RS-68 engines cut off, and the Ares V core was jettisoned to burn up in Earth's atmosphere. Upon separation using the on-board staging and [[Engineering:Ullage motor|ullage motor]]s, the single J-2X engine would then have fired at full thrust to place itself and the Altair into a [[Astronomy:Low Earth orbit|low Earth orbit]] until it was retrieved, via a separate launch on an Ares I, by the [[Engineering:Orion (spacecraft)|Orion MPCV]] and its four-person astronaut crew.

Once the Orion was docked with the Altair and its systems were checked out, the crew was to jettison the loiter skirt and then fire the J-2X engine for a second time, this time at 80% rated thrust, for [[Astronomy:Trans-lunar injection|trans-lunar injection]] (TLI).  Unlike the S-IVB, which propelled the Apollo spacecraft and its three-man crew in a forward-facing motion, the EDS would have fired with the crew ''facing'' the EDS.  This "eyeballs out" type of flying would be similar to the flight profile of the proposed, but never flown Manned Venus Flyby, from the cancelled [[Astronomy:Apollo Applications Program|Apollo Applications Program]] of the late 1960s.

When TLI was completed and the EDS was shut down for the last time, it would then have been jettisoned to fly into a [[Astronomy:Heliocentric orbit|heliocentric orbit]], or in a manner similar to that employed by NASA from [[Engineering:Apollo 13|Apollo 13]] to [[Engineering:Apollo 17|Apollo 17]], it may have been deliberately crashed into the lunar surface to help scientists calibrate sensitive seismometers placed on the lunar surface by either astronauts on [[Astronomy:Lunar sortie|lunar sortie]] flights or by uncrewed robotic probes.<ref>{{cite web |url=http://www.nasa.gov/mission_pages/constellation/ares/aresV.html |title=Ares V Cargo Launch Vehicle |publisher=NASA}}</ref>

==Space Launch System==
When the Ares program was cancelled in favor of the [[Astronomy:Space Launch System|Space Launch System]], the EDS was considered as a second stage for the Block 1B SLS.<ref>{{cite web|url=http://www.nasaspaceflight.com/2012/03/sls-specifications-take-shape-development-continues/|title=SLS Launch Vehicle specifications take shape as development continues|website=NASASpaceflight.com|date=16 March 2012 |access-date=July 24, 2014}}</ref> This version of the stage would have been about {{Convert|80|ft}} long and equipped with one to three J-2X engines.<ref name="NSFUS">{{cite web|url=http://www.nasaspaceflight.com/2011/11/sls-j-2x-upper-stage-engine-500-second-test-fire/|title=SLS J-2X Upper Stage engine enjoys successful 500 second test fire|date=9 November 2011|publisher=NASASpaceflight.com|access-date=25 January 2012|author=Chris Bergin}}</ref> Technological development of the J-2X was expected to take considerably more time, so the EDS was dropped in favor of the [[Engineering:Exploration Upper Stage|Exploration Upper Stage]], which will use the much lower-thrust but already-developed RL10.  According to NASA, the J-2X will be overpowered for the [[Astronomy:Artemis program|Artemis program]]; its development has been put on hold (though not abandoned) until stages capable of transferring heavy payloads to Mars are required (expected in the 2030s).<ref>{{Cite web|last=Goldenberg|first=Jacob|date=2013-12-04|title=NASA's J-2X Engine To Be Mothballed After Testing|url=https://aviationweek.com/defense-space/space/nasas-j-2x-engine-be-mothballed-after-testing|url-status=live|archive-url=http://aviationweek.com/awin/nasa-s-j-2x-engine-be-mothballed-after-testing|archive-date=2021-07-09|access-date=2016-08-16|website=aviationweek.com}}</ref>

==References==
{{Include-NASA}}
{{reflist}}

{{Upper stages}}
{{Project Constellation}}
{{J-2 (rocket engine)}}


[[Category:Rocket stages]]

{{Sourceattribution|Earth Departure Stage}}