Editing Space rendezvous (section)

===First attempt failed===

NASA's first attempt at rendezvous was made on June 3, 1965, when US astronaut [[Jim McDivitt]] tried to maneuver his [[Gemini 4]] craft to meet its spent [[Titan II GLV|Titan II launch vehicle]]'s upper stage. McDivitt was unable to get close enough to achieve station-keeping, due to depth-perception problems, and stage propellant venting which kept moving it around.<ref name="mcdivittoh">Oral History Transcript / [http://www.jsc.nasa.gov/history/oral_histories/McDivittJA/mcdivittja.pdf James A. McDivitt] {{Webarchive|url=https://web.archive.org/web/20160304130319/http://www.jsc.nasa.gov/history/oral_histories/McDivittJA/mcdivittja.pdf |date=March 4, 2016 }} / Interviewed by Doug Ward / Elk Lake, Michigan – June 29, 1999</ref>
However, the Gemini 4 attempts at rendezvous were unsuccessful largely because [[NASA]] engineers had yet to learn the [[orbital mechanics]] involved in the process. Simply pointing the active vehicle's nose at the target and thrusting was unsuccessful. If the target is ahead in the orbit and the tracking vehicle increases speed, its altitude also increases, actually moving it away from the target. The higher altitude then increases orbital period due to [[Kepler's laws of planetary motion#Third law|Kepler's third law]], putting the tracker not only above, but also behind the target. The proper technique requires changing the tracking vehicle's orbit to allow the rendezvous target to either catch up or be caught up with, and then at the correct moment changing to the same orbit as the target with no relative motion between the vehicles (for example, putting the tracker into a lower orbit, which has a shorter orbital period allowing it to catch up, then executing a [[Hohmann transfer orbit|Hohmann transfer]] back to the original orbital height).<ref name="gemini-4-ea">{{Cite web |url=http://www.astronautix.com/flights/gemini4.htm |title=Gemini 4 |publisher=Encyclopedia Astronautica |url-status=dead |archive-url=https://web.archive.org/web/20101129073633/http://astronautix.com/flights/gemini4.htm |archive-date=November 29, 2010 |df=mdy-all }}</ref>

{{quote|As [[Project Gemini|GPO]] engineer André Meyer later remarked, "There is a good explanation for what went wrong with rendezvous." The crew, like everyone else at [[Manned Spacecraft Center|MSC]], "just didn't understand or reason out the [[orbital mechanics]] involved. As a result, we all got a whole lot smarter and really perfected rendezvous maneuvers, which [[Apollo program|Apollo]] now uses."|<ref name="gemini-4-ea" />}}