Editing Earth orbit rendezvous

{{short description|Method for conducting round trip human flights to the Moon}}
[[File:Gemini 6 7.jpg|thumb|200px|[[Gemini 7]] as seen from [[Gemini 6]] during their rendezvous in Earth orbit in 1965 (NASA)]]
'''Earth orbit rendezvous''' ('''EOR''') is a method for conducting round trip human flights to the Moon, involving the use of [[space rendezvous]] to assemble, and possibly fuel, components of a translunar vehicle in [[low Earth orbit]].<ref>"LOW EARTH ORBIT RENDEZVOUS STRATEGY FOR LUNAR MISSIONS" http://www.informs-sim.org/wsc06papers/158.pdf</ref> It was considered as an alternative to direct ascent but ultimately rejected in favor of [[lunar orbit rendezvous]] (LOR) for [[NASA]]'s [[Apollo program]] of the 1960s and 1970s,<ref>{{Cite book |last=Launius |first=Roger D. |url=http://www.jstor.org/stable/j.ctvhrcxzx |title=Reaching for the Moon: A Short History of the Space Race |date=2019-06-25 |publisher=Yale University Press |isbn=978-0-300-24516-5 |doi=10.2307/j.ctvhrcxzx|jstor=j.ctvhrcxzx }}</ref> mainly because LOR does not require a spacecraft big enough to both make the return trip from Earth orbit to splash down in the ocean and a soft landing on the lunar surface.<ref>"Lunar Orbit Rendezvous and the Apollo Program" http://www.nasa.gov/centers/langley/news/factsheets/Rendezvous.html {{Webarchive|url=https://web.archive.org/web/20130406180052/http://www.nasa.gov/centers/langley/news/factsheets/Rendezvous.html |date=2013-04-06 }}</ref> The two main proposed methodologies were: the in-space assembly of fueled spacecraft modules via docking techniques; and the in-space refueling of fully assembled spacecraft.<ref>{{Cite journal |last=Holmes |first=Brainerd |date=October 1962 |title=Manned Space Flight |journal=[[AIBS Bulletin]] |publisher=[[Oxford University Press]] |volume=12 |issue=5 |pages=56–9 |doi=10.2307/1293010|jstor=1293010 }}</ref> This was the preferred approach adopted by the Soviet Union for achieving human lunar missions.<ref>{{Cite news |last=Simons |first=Howard |date=March 28, 1965 |title=Historic Flight Prove Moon Race Is On |work=[[The Miami Herald]]}}</ref>

Three decades later, it was planned to be used for [[Project Constellation]], until that program's [[Barack Obama space policy speech at Kennedy Space Center|cancellation in October 2010]].<ref>Connolly, John F. (October 2006). "Constellation Program Overview" http://www.nasa.gov/pdf/163092main_constellation_program_overview.pdf {{Webarchive|url=https://web.archive.org/web/20070710060512/http://www.nasa.gov/pdf/163092main_constellation_program_overview.pdf |date=2007-07-10 }}</ref>

==Gemini and Agena target vehicle==
The [[Agena target vehicle]] (ATV) was used for testing Earth orbit rendezvous in the NASA [[Gemini Program]]. [[Gemini 6]] and [[Gemini 7]] rendezvoused in orbit in 1965, but without Agena. Next, [[Gemini 8]] successfully docked  with the Agena on March 16, 1966. The Agena-Gemini rendezvous also achieved other objectives in later Gemini launches, including docked orbital maneuvering ([[Gemini 10]] and [[Gemini 11]]), inspection of the abandoned Gemini 8 ATV (Gemini 10) and space walks ([[Gemini 12]]).<ref>{{Cite book |title=Spaceflight : the complete story from Sputnik to shuttle -- and beyond|last=Sparrow|first=Giles|date=2007|publisher=Dorling Kindersley |isbn=9781405318181|location=London|pages=110|oclc=124970031}}</ref>

==Apollo==
[[File:Apollo Earth Orbit Rendezvous - 10 launches required.jpg|thumb|200px|1961 sketch showing 10 C-1 launches required to assemble in Earth orbit an Apollo lunar landing mission.]]
The EOR proposal for Apollo consisted of using a series of small rockets half the size of a [[Saturn V]] to put different components of a spacecraft to go to the Moon in orbit around the Earth, then assemble them in orbit.  Experiments of [[Project Gemini]] involving docking with the [[Agena target vehicle]] were designed partly to test the feasibility of this program.{{citation needed|date=October 2016}}

In the end, NASA employed the [[Lunar Orbit Rendezvous]] for the [[Project Apollo|Apollo Program]]: a  Saturn V would simultaneously lift both the [[Apollo Command Module|Apollo Command]] and [[Apollo Lunar Module|Lunar Modules]] into low Earth orbit, and then the Saturn V third stage would fire again ([[Trans-lunar injection]]) to send both spacecraft to the Moon.<ref>{{cite web
 | title = Chariots for Apollo: A History of Manned Lunar Spacecraft
 | publisher = [[NASA]]
 | year = 1979
 | url = https://history.nasa.gov/SP-4205/ch3-2.html
 | accessdate = 2007-04-27|archiveurl=https://web.archive.org/web/20041118232618/https://history.nasa.gov/SP-4205/ch3-2.html|archivedate=2004-11-18}}</ref>

==Constellation==
This mode had been revived for [[Project Constellation]] as the [[Earth Departure Stage]] (EDS) and [[Altair (spacecraft)|Altair]] (LSAM), which would be launched into low Earth orbit on the [[Ares V]] rocket.  The EDS and Altair would  be met by the separately launched [[Orion (Constellation program)|Orion]] (CEV). Once joined in low Earth orbit, the three would then travel out to the Moon, and the Orion/Altair combination would fly a [[lunar orbit rendezvous]] flight pattern.{{Citation needed|date=September 2010}}

==References==
{{Reflist}}

{{DEFAULTSORT:Earth Orbit Rendezvous}}
[[Category:Spaceflight]]
[[Category:Apollo program]]
[[Category:Space rendezvous]]


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