View source for Saturn I SA-4

{{Short description|March 1963 Apollo program test launch}}
{{Infobox spaceflight
| name                  = Saturn I SA-4
| image                 = Saturn SA4 on launch pad.jpg
| image_caption         = SA-4 on [[Cape Canaveral Air Force Station Launch Complex 34|Pad 34]]

| mission_type          = Test flight
| operator              = [[NASA]] 
| mission_duration      = 15&nbsp;minutes
| suborbital_apogee     = {{convert|129|km|mi|sp=us}}
| distance_travelled    = {{convert|400|km|mi|sp=us}}

| spacecraft            = 
| manufacturer          = 
| launch_mass           = {{convert|52480|kg|lb}}
| landing_mass          =

| launch_date           = {{start-date|March 28, 1963, 20:11:55|timezone=yes}}&nbsp;UTC 
| launch_rocket         = Saturn I
| launch_site           = [[Cape Canaveral Air Force Station|Cape Canaveral]] [[Cape Canaveral Air Force Station Launch Complex 34|LC-34]]
| decay_date            = {{end-date|March 28, 1963, 20:26:55|timezone=yes}}&nbsp;UTC

| previous_mission      = [[Saturn I SA-3]]
| next_mission          = [[Saturn I SA-5]]
| programme             = [[Apollo program|Project Apollo]]<br/><small>Uncrewed tests</small>
}}

'''Saturn-Apollo 4''' ('''SA-4''') was the fourth launch of a [[Saturn I]] launch vehicle and the last of the initial test phase of the first stage. It was part of the [[Project Apollo|Apollo Program]].

==Objectives==
SA-4 was the last flight to test only the S-I first stage of the Saturn I rocket. As with the first three launches this would be a suborbital flight and would test the structural integrity of the rocket.

The major addition to this flight was that, in order to test the rocket's ability to deal with an engine failure during the flight, one of the engines would be programmed to shut down about 100 seconds after launch. If all went well the rocket would reroute the fuel for this engine to the other engines and have the rocket burn longer to compensate for the loss of acceleration. This was used successfully on the later [[Apollo 6]] and [[Apollo 13]] flights (both [[Saturn V]] rockets).

Also on this flight, the dummy second stage was outfitted with the aerodynamic design of the real second stage. This included vent ducts, fairings and dummy camera pods. The rocket also flew with antennae designed for the Block II version of the rocket.

==Flight==
After the shortest checkout time of any rocket at 54 days,{{Citation needed|date=May 2010}} SA-4 went on to experience the longest series of holds of any mission at 120 minutes.{{Citation needed|date=May 2010}} The SA-4 launch would be the final single-stage flight.

The rocket operated perfectly through the first 100 seconds of the flight, when the No. 5 engine shut off as planned. The rocket then continued to operate properly, the propellant system rerouting the fuel to the other engines.  The No. 5 engine did not disintegrate because of heat caused by the lack of cooling propellant as some had predicted. This was an important test proving an important feature of the clustered engine design.

The rocket reached a maximum height of 129&nbsp;km and a peak velocity of 5906&nbsp;km per hour. At this stage it also fired retrorockets that would be used on later missions to separate the rocket stages. On SA-4 the stages were not designed to separate but tested the retrorockets to make sure they would fire.

==External links==
{{Commons category|Saturn-Apollo 4}}
*[https://www.youtube.com/watch?v=jlK60KWjTdA Saturn I SA-4 Launch Video]
*[http://www.hq.nasa.gov/office/pao/History/SP-4009/cover.htm The Apollo Spacecraft: A Chronology] {{Webarchive|url=https://web.archive.org/web/20171209084600/http://www.hq.nasa.gov/office/pao/History/SP-4009/cover.htm |date=2017-12-09 }}
*[https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=SATURNSA4 NASA Space Science Data Coordinated Archive]
*[http://www.hq.nasa.gov/office/pao/History/SP-4204/cover.html Moonport: A History of Apollo Launch Facilities and Operations] {{Webarchive|url=https://web.archive.org/web/20110318012712/http://www.hq.nasa.gov/office/pao/History/SP-4204/cover.html |date=2011-03-18 }}
*http://science.ksc.nasa.gov/history/apollo/sa-4/sa-4.html {{Webarchive|url=https://web.archive.org/web/20080916091302/http://science.ksc.nasa.gov/history/apollo/sa-4/sa-4.html |date=2008-09-16 }}
*[https://history.nasa.gov/SP-4206/sp4206.htm Stages to Saturn]

{{Include-NASA}}

{{Apollo program| before=[[SA-3 (Apollo)|SA-3]]| after=[[SA-5 (Apollo)|SA-5]] <br> [[Pad Abort Test-1]] <br> [[QTV]]}}

{{Use American English|date=January 2014}}

[[Category:Apollo program]]
[[Category:1963 in spaceflight]]
[[Category:Test spaceflights]]
[[Category:Spacecraft launched by Saturn rockets]]
[[Category:Saturn I]]