Editing Sputnik 1 (section)

== Launch and mission ==
[[File:Dawn of the Space Age.jpg|thumb|upright=1.0|left|Artist's impression of ''Sputnik 1'' in orbit]]
The control system of the Sputnik rocket was adjusted to an intended orbit of {{cvt|223|by|1450|km}}, with an orbital period of 101.5 minutes.<ref name="MainR">[http://epizodsspace.testpilot.ru/bibl/vetrov/korolev-delo/03-03.html#36 Main Results of the Launch of the Rocket with the First ISZ Onboard on 4 October 1957] {{webarchive |url=https://web.archive.org/web/20071002142544/http://epizodsspace.testpilot.ru/bibl/vetrov/korolev-delo/03-03.html|date=2 October 2007}} – document signed by S.P. Korolev, V.P. Glushko, N.A. Pilyugin and V.P. Barmin, in the book by Vetrov "Korolev and His Job" {{in lang|ru}}</ref> The trajectory had been calculated earlier by [[Georgi Grechko]], using the [[Academy of Sciences of the Soviet Union|USSR Academy of Sciences]]' [[mainframe computer]].<ref name="NKA" /><ref>Siddiqi, p. 154.</ref>

The Sputnik rocket was launched on 4 October 1957 at 19:28:34 [[Coordinated Universal Time|UTC]] (5 October at the launch site<ref name="rswSM">{{cite web |url=http://www.russianspaceweb.com/sputnik_mission.html|title=Sputnik's mission|year=2015|publisher=RussianSpaceWeb.com|access-date=27 December 2015|archive-url=https://web.archive.org/web/20130123225622/http://russianspaceweb.com/sputnik_mission.html|archive-date=23 January 2013|first1=Anatoly|last1=Zak}}</ref><ref name="nssdc.orbit">{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/displayTrajectory.action?id=1957-001B|title=Trajectory: Sputnik-1 1957-001B|publisher=NASA|date=27 April 2021|access-date=16 May 2021}} {{Source-attribution}}</ref>) from [[Gagarin's Start|Site No.1]] at NIIP-5.<ref>{{cite web|url=http://www.tecnocosmos.com/archivo/1957/1957001b.htm|archive-url=https://web.archive.org/web/20070927180255/http://www.tecnocosmos.com/archivo/1957/1957001b.htm|url-status=dead|title=Sputnik 1|archive-date=27 September 2007|language=es}}</ref> Telemetry indicated that the strap-ons separated 116 seconds into the flight and the core stage engine shut down 295.4 seconds into the flight.<ref name="MainR" /> At shutdown, the 7.5-tonne core stage (with PS-1 attached) had attained an altitude of {{cvt|223|km}} above sea level, a velocity of {{cvt|7780|m/s}}, and a velocity vector inclination to the local horizon of 0 degrees 24 minutes. This resulted in an initial elliptical orbit of {{cvt|223|km}} by {{cvt|950|km}}, with an apogee approximately {{cvt|500|km}} lower than intended, and an [[orbital inclination|inclination]] of 65.10° and a period of 96.20 minutes.<ref name="MainR" /><ref name=":23"/>

Several engines did not fire on time, almost aborting the mission.<ref name=":23"/> A fuel regulator in the booster also failed around 16 seconds into launch, which resulted in excessive [[RP-1]] consumption for most of the powered flight and the engine thrust being 4% above nominal. Core stage cutoff was intended for T+296 seconds, but the premature propellant depletion caused thrust termination to occur one second earlier when a sensor detected overspeed of the empty RP-1 turbopump. There were {{cvt|375|kg}} of [[liquid oxygen|LOX]] remaining at cutoff.<ref name="rswSM" />

At 19.9 seconds after engine cut-off, PS-1 separated from the second stage<ref name="rswSM" /> and the satellite's transmitter was activated. These signals were detected at the IP-1 station by Junior Engineer-Lieutenant V.G. Borisov, where reception of Sputnik 1's "beep-beep-beep" tones confirmed the satellite's successful deployment. Reception lasted for two minutes, until PS-1 passed below the horizon.<ref name="NKA" /><ref>[http://epizodsspace.testpilot.ru/bibl/ziv/2002/5-kak-zap.html How the First Sputnik Was Launched] {{webarchive |url=https://web.archive.org/web/20080408030050/http://epizodsspace.testpilot.ru/bibl/ziv/2002/5-kak-zap.html|date=8 April 2008}} at ''Zemlya i Vselennaya'' magazine, No.5, 2002 {{in lang|ru}}</ref> The Tral telemetry system on the R-7 core stage continued to transmit and was detected on its second orbit.<ref name="rswSM" />

The designers, engineers, and technicians who developed the rocket and satellite watched the launch from the range.<ref name="VR">{{cite web|title=World's first satellite and the international community's response|publisher=VoR.ru|url=http://www.vor.ru/Space_now/Satellite/Satellite_102_eng.html|access-date=22 January 2007|archive-url=https://web.archive.org/web/20070912141057/http://www.vor.ru/Space_now/Satellite/Satellite_102_eng.html|archive-date=12 September 2007}}</ref> After the launch they drove to the mobile radio station to listen for signals from the satellite.<ref name="VR" /> They waited about 90 minutes to ensure that the satellite had made one orbit and was transmitting before Korolev called Soviet premier [[Nikita Khrushchev]].<ref name="redmoonPN">Brzezinski, pp. 158–159</ref>

On the first orbit the [[Telegraph Agency of the Soviet Union]] (TASS) transmitted: "As result of great, intense work of scientific institutes and design bureaus the first artificial Earth satellite has been built".<ref>{{cite web|script-title=ru:Спутник-1 – начало космической эры|publisher=Rustrana.ru|language=ru|date=21 July 2005|url=http://www.rustrana.ru/article.php?nid=4632|access-date=4 October 2007|archive-url=https://web.archive.org/web/20070929084309/http://www.rustrana.ru/article.php?nid=4632|archive-date=29 September 2007}}</ref> The R-7 core stage, with a mass of 7.5 tonnes and a length of 26 metres, also reached Earth orbit. It was a [[Apparent magnitude|first magnitude]] object following behind the satellite and visible at night. Deployable reflective panels were placed on the booster in order to increase its visibility for tracking.<ref name="redmoonPN" /> A small highly polished sphere, the satellite was barely visible at sixth magnitude, and thus harder to follow optically.<ref name="1957sat" /> The batteries ran out on 26 October 1957, after the satellite completed 326 orbits.<ref>{{cite news|url=https://www.newspapers.com/clip/27956829/argusleader/|title=Reds Say Sputnik's Batteries Worn Out|agency=Associated Press |date=October 26, 1957|newspaper=Argus-Leader|location=Sioux Falls, South Dakota|page=1|via=Newspapers.com}}</ref>

The core stage of the R-7 remained in orbit for two months until 2 December 1957, while Sputnik 1 orbited for three months, until 4 January 1958, having completed 1,440 orbits of the Earth.<ref name="rswSM" />