Editing Apollo 8 (section)

===Launch and trans-lunar injection===

[[File:Apollo 8 liftoff.jpg|thumb|Apollo 8 launch]]

Apollo 8 was launched at 12:51:00 [[UTC]] (07:51:00 [[Eastern Time Zone (North America)|Eastern Standard Time]]) on December 21, 1968, using the Saturn V's [[Multistage rocket|three stages]] to achieve Earth orbit.{{sfn|Orloff|2000|p=39}} The [[S-IC]] first stage landed in the [[Atlantic Ocean]] at {{Coord|30|12|N|74|7|W|name=Apollo 8 S-IC impact}}, and the [[S-II]] second stage landed at {{Coord|31|50|N|37|17|W|name=Apollo 8 S-II impact}}.{{sfn|Orloff|2000|p=34}} The [[S-IVB]] third stage injected the craft into Earth orbit and remained attached to perform the TLI burn that would put the spacecraft on a trajectory to the Moon.{{sfn|Orloff|2000|p=35}}

Once the [[space vehicle|vehicle]] reached Earth orbit, both the crew and [[Christopher C. Kraft Jr. Mission Control Center|Houston flight controllers]] spent the next 2{{nbsp}}hours and 38 minutes checking that the spacecraft was in proper working order and ready for TLI.{{sfn|Brooks|Grimwood|Swenson|1979|p=276}} The proper operation of the S-IVB third stage of the rocket was crucial, and in the last uncrewed test, it had failed to reignite for this burn.{{sfn|Brooks|Grimwood|Swenson|1979|pp=250–252}} Collins was the first CAPCOM on duty, and at 2{{nbsp}}hours, 27 minutes and 22 seconds after launch he radioed, "Apollo{{nbsp}}8. You are Go for TLI."{{sfn|Brooks|Grimwood|Swenson|1979|p=276}} This communication meant that Mission Control had given official permission for Apollo{{nbsp}}8 to go to the Moon. The S-IVB engine ignited on time and performed the TLI burn perfectly.{{sfn|Brooks|Grimwood|Swenson|1979|p=276}} Over the next five minutes, the spacecraft's speed increased from {{convert|7600|to|10800|m/s|sp=us}}.{{sfn|Brooks|Grimwood|Swenson|1979|p=276}}

After the S-IVB had placed the mission on course for the Moon, the command and service modules (CSM), the remaining Apollo{{nbsp}}8 spacecraft, separated from it. The crew then rotated the spacecraft to take photographs of the spent stage and then practiced flying in formation with it. As the crew rotated the spacecraft, they had their first views of the Earth as they moved away from it—this marked the first time humans had viewed the whole Earth at once. Borman became worried that the S-IVB was staying too close to the CSM and suggested to Mission Control that the crew perform a separation maneuver. Mission Control first suggested pointing the spacecraft towards Earth and using the small [[Apollo CSM#Reaction control system|reaction control system]] (RCS) thrusters on the [[Apollo command and service module#Service module (SM)|service module]] (SM) to add {{convert|1.1|ft/s|m/s|abbr=on|sp=us}} to their velocity away from the Earth, but Borman did not want to lose sight of the S-IVB. After discussion, the crew and Mission Control decided to burn in the Earth direction to increase speed, but at {{convert|7.7|ft/s|m/s|abbr=on}} instead. The time needed to prepare and perform the additional burn put the crew an hour behind their onboard tasks.{{sfn|Orloff|2000|p=35}}{{sfn|Brooks|Grimwood|Swenson|1979|pp=276–278}}
[[File:As8-16-2583.jpg|thumb|Apollo 8 [[S-IVB]] rocket stage shortly after separation. The LM test article, a circular boilerplate model of the LM, is visible with four triangular legs connecting it to the stage.]]

Five hours after launch, Mission Control sent a command to the S-IVB to vent its remaining fuel, changing its trajectory. The S-IVB, with the test article attached, posed no further hazard to Apollo{{nbsp}}8, passing the orbit of the Moon and going into a {{convert|0.99|by|0.92|AU|Gm|lk=on|adj=on}} solar orbit with an [[inclination]] of 23.47° from the Earth's equatorial plane, and an orbital period of 340.80 days.{{sfn|Orloff|2000|p=35}} It became a [[:Category:Derelict satellites in heliocentric orbit|derelict object]], and will continue to [[heliocentric orbit|orbit the Sun]] for many years, if not retrieved.<ref name=ha20130923>{{cite web|title=Saturn S-IVB-503N—Satellite Information |url=http://www.heavens-above.com/SatInfo.aspx?satid=3627&lat=0&lng=0&loc=Unspecified&alt=0&tz=UCT |work=Satellite database |publisher=Heavens-Above |access-date=September 23, 2013}}</ref>

The Apollo 8 crew were the first humans to pass through the [[Van Allen radiation belt]]s, which extend up to {{convert|15000|mi|km}} from Earth. Scientists predicted that passing through the belts quickly at the spacecraft's high speed would cause a radiation dosage of no more than a chest [[X-ray]], or 1{{nbsp}}[[Gray (unit)|milligray]] (mGy; during a year, the average human receives a dose of 2{{nbsp}}to 3{{nbsp}}mGy from [[background radiation]]). To record the actual radiation dosages, each crew member wore a Personal Radiation [[Dosimeter]] that transmitted data to Earth, as well as three passive film dosimeters that showed the cumulative radiation experienced by the crew. By the end of the mission, the crew members experienced an average radiation dose of 1.6 mGy.<ref name="Biomedical">{{cite book|last=Bailey |first=J. Vernon |title=Biomedical Results of Apollo |url=http://lsda.jsc.nasa.gov/books/apollo/eboard2.htm |archive-url=https://web.archive.org/web/20080117135912/http://lsda.jsc.nasa.gov/books/apollo/S2ch3.htm |archive-date=January 17, 2008 |access-date=January 28, 2008 |year=1975 |publisher=[[Lyndon B. Johnson Space Center]] |id=[https://history.nasa.gov/SP-368/sp368.htm NASA SP-368] |chapter=Radiation Protection and Instrumentation |chapter-url=http://lsda.jsc.nasa.gov/books/apollo/S2ch3.htm |url-status=dead}} Sec. 2, Ch. 3.</ref>