Editing Apollo 12 (section)

== Hardware ==
=== Launch vehicle ===
[[File:Saturn V Apollo 12.jpg|thumb|upright|SA-507 en route to the launch pad, September 1969]]

There were no significant changes to the [[Saturn V]] launch vehicle used on Apollo 12,{{sfn|Mission Report|p=A–1}} SA–507, from that used on Apollo 11. There were another 17 instrumentation measurements in the Apollo 12 launch vehicle, bringing the number to 1,365.{{sfn|Press Kit|p=50}} The entire vehicle, including the spacecraft, weighed {{convert|6,487,742|lb}} at launch, an increase from Apollo 11's {{convert|6,477,875|lb}}. Of this figure, the spacecraft weighed {{convert|110,044|lb}}, up from {{convert|109,646|lb}} on Apollo 11.{{sfn|Orloff & Harland 2006|p=585}}

==== Third stage trajectory ====
After LM separation, the third stage of the Saturn V, the [[S-IVB]], was intended to fly into solar orbit. The S-IVB auxiliary propulsion system was fired, with the intent that the Moon's gravity would [[gravity assist|slingshot]] the stage into solar orbit. Due to an error, the S-IVB flew past the Moon at too high an altitude to achieve Earth escape velocity. It remained in a semi-stable Earth orbit until it finally escaped Earth orbit in 1971, but briefly returned to Earth orbit 31 years later. It was discovered by amateur astronomer [[William Kwong Yu Yeung|Bill Yeung]] who gave it the temporary designation [[J002E3]] before it was determined to be an artificial object. Again in solar orbit as of 2021, it may again be captured by Earth's gravity, but not at least until the 2040s.<ref name=NASA>{{cite news|url=http://neo.jpl.nasa.gov/news/news136.html |title=J002E3: An Update |publisher=nasa.gov |first1=Paul |last1=Chodas |first2=Steve |last2=Chesley|date=October 9, 2002 |access-date=September 18, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20030503111617/http://neo.jpl.nasa.gov/news/news136.html |archive-date=May 3, 2003}}</ref><ref name=Jorgensen>{{cite journal |last1=Jorgensen |first1=K. |last2=Rivkin |first2=A. |last3=Binzel |first3=R. |last4=Whitely |first4=R. |last5=Hergenrother |first5=C. |last6=Chodas |first6=P. |last7=Chesley |first7=S. |last8=Vilas |first8=F |title=Observations of J002E3: Possible Discovery of an Apollo Rocket Body |journal=Bulletin of the American Astronomical Society |date =May 2003 |volume=35 |page=981 |bibcode = 2003DPS....35.3602J}}</ref> The S-IVBs used on later lunar missions were deliberately crashed into the Moon to create seismic events that would register on the seismometers left on the Moon and provide data about the Moon's structure.{{sfn|Orloff & Harland 2006|pp=340–341}}

=== Spacecraft ===
[[File:Apollo 12 command and service modules hoisted above test stand.jpg|thumb|upright|The Apollo 12 CSM on a test stand, June 30, 1969]]

The Apollo 12 spacecraft consisted of Command Module 108 and Service Module 108 (together Command and Service Modules 108, or CSM–108), Lunar Module 6 (LM–6), a Launch Escape System (LES), and Spacecraft-Lunar Module Adapter 15 (SLA–15). The LES contained three rocket motors to propel the CM to safety in the event of an abort shortly after launch, while the SLA housed the LM and provided a structural connection between the Saturn V and the LM.{{sfn|Orloff & Harland 2006|p=330}}{{sfn|Press Kit|p=53}} The SLA was identical to Apollo 11's, while the LES differed only in the installation of a more reliable motor igniter.{{sfn|Mission Report|p=A–1}}

The CSM was given the [[call sign]] ''Yankee Clipper'', while the LM had the call sign ''Intrepid''.{{sfn|Orloff & Harland 2006|p=328}} These sea-related names were selected by the all-Navy crew from several thousand proposed names submitted by employees of the prime contractors of the respective modules.<ref>{{cite news|newspaper=[[The New York Times]]|date=November 15, 1969|url=https://timesmachine.nytimes.com/timesmachine/1969/11/15/79436944.html?pageNumber=24|title=Apollo spaceships have name with salty ring|url-access=subscription}}</ref> George Glacken, a flight test engineer at [[North American Aviation]], builder of the CSM, proposed ''Yankee Clipper'' as such ships had "majestically sailed the high seas with pride and prestige for a new America". ''Intrepid'' was from a suggestion by Robert Lambert, a planner at [[Grumman]], builder of the LM, as evocative of "this nation's resolute determination for continued exploration of space, stressing our astronauts' fortitude and endurance of hardship".{{sfn|Harland 2011|p=12}}

The differences between the CSM and LM of Apollo 11, and those of Apollo 12, were few and minor.{{sfn|Mission Report|p=A–1}} A hydrogen separator was added to the CSM to stop the gas from entering the potable water tank—Apollo 11 had had one, though mounted on the water dispenser in the CM's cabin.{{sfn|Press Kit|p=57}} Gaseous hydrogen in the water had given the Apollo 11 crew severe flatulence.{{sfn|Harland 2011|p=150}} Other changes included the strengthening of the recovery loop attached following splashdown, meaning that the swimmers recovering the CM would not have to attach an auxiliary loop.{{sfn|Press Kit|p=57}} LM changes included a structural modification so that scientific experiment packages could be carried for deployment on the lunar surface.{{sfn|Press Kit|p=63}} Two hammocks were added for greater comfort of the astronauts while resting on the Moon, and [[Apollo TV camera|a color television camera]] substituted for the black and white one used on the lunar surface during Apollo 11.{{sfn|Mission Report|p=A–2}}

=== ALSEP ===
{{Main|Apollo Lunar Surface Experiments Package}}
[[File:ALSEP AS12-47-6917.jpg|thumb|left|Apollo 12's Passive Seismic Experiment]]

The [[Apollo Lunar Surface Experiments Package]] (ALSEP) was a suite of scientific instruments designed to be emplaced on the lunar surface by the Apollo astronauts, and thereafter operate autonomously, sending data to Earth.<ref name = "astro" /> Development of the ALSEP was part of NASA's response to some scientists who opposed the crewed lunar landing program (they felt that robotic craft could explore the Moon more cheaply) by demonstrating that some tasks, such as deployment of the ALSEP, required humans.{{sfn|Harland 2011|pp=265–266}} In 1966, a contract to design and build the ALSEPs was awarded to the [[Bendix Corporation]].<ref>{{cite news|title=NASA giving Bendix $17 million lunar pact|url=https://aadl.org/aa_news_19660317_p29-nasa_giving_bendix_17_million_lunar_pact|newspaper=[[Ann Arbor News]]|date=March 17, 1966}}</ref> Due to the limited time the Apollo 11 crew would have on the lunar surface, a smaller suite of experiments was flown, known as the Early Apollo Surface Experiment Package (EASEP). Apollo 12 was the first mission to carry an ALSEP; one would be flown on each of the subsequent lunar landing missions, though the components that were included would vary.<ref name = "astro" /> Apollo 12's ALSEP was to be deployed at least {{convert|300|ft}} away from the LM to protect the instruments from the debris that would be generated when the ascent stage of the LM took off to return the astronauts to lunar orbit.{{sfn|Harland 2011|p=279}}

[[File:Putting the Plutonium 238 fuel into the SNAP 27.jpg|thumb|left|Bean places the fuel element into the SNAP-27 RTG.]]

Apollo 12's ALSEP included a [[Lunar Surface Magnetometer]] (LSM), to measure the magnetic field at the Moon's surface, a Lunar Atmosphere Detector (LAD, also known as the [[Cold Cathode Gauge Experiment]]), intended to measure the density and temperature of the thin lunar atmosphere and how it varies, a Lunar Ionosphere Detector (LID, also known as the [[Suprathermal Ion Detector Experiment]], or SIDE), intended to study the charged particles in the lunar atmosphere, and the [[Solar Wind Spectrometer]], to measure the strength and direction of the [[solar wind]] at the Moon's surface—the free-standing Solar Wind Composition Experiment, to measure what makes up the solar wind, would be deployed and then brought back to Earth by the astronauts.{{sfn|Press Kit|pp=30–36}} A Dust Detector was used to measure the accumulation of [[lunar dust]] on the equipment.{{sfn|Press Kit|p=42}} [[Apollo 12 Passive Seismic Experiment|Apollo 12's Passive Seismic Experiment]] (PSE), a seismometer, would measure moonquakes and other movements in the Moon's crust, and would be calibrated by the nearby planned impact of the ascent stage of Apollo 12's LM, an object of known mass and velocity hitting the Moon at a known location, and projected to be equivalent to the explosive force of one ton of TNT.{{sfn|Press Kit|p=40}}

The ALSEP experiments left on the Moon by Apollo 12 were connected to a Central Station, which contained a transmitter, receiver, timer, data processor, and equipment for power distribution and control of the experiments.{{sfn|Mission Report|p=A-5}} The equipment was powered by [[SNAP-27]], a [[radioisotope thermoelectric generator]] (RTG) developed by the [[United States Atomic Energy Commission|Atomic Energy Commission]]. Containing [[plutonium]], the RTG flown on Apollo 12 was the first use of atomic energy on a crewed NASA spacecraft—some NASA and military satellites had previously used similar systems. The plutonium core was brought from Earth in a cask attached to an LM landing leg, a container designed to survive re-entry in the event of an aborted mission, something NASA considered unlikely.{{sfn|Press Kit|pp=33–34}} The cask would survive re-entry on [[Apollo 13]], sinking in the [[Tonga Trench]] of the Pacific Ocean, apparently without radioactive leakage.<ref name = "Cass 3">{{cite web|last=Cass|first=Stephen|title=Houston, we have a solution, part 3|url=https://spectrum.ieee.org/apollo-13-we-have-a-solution-part-3|date=April 1, 2005|website=IEEE|access-date=September 8, 2019}}</ref>

The Apollo 12 ALSEP experiments were activated from Earth on November 19, 1969.{{sfn|Orloff & Harland 2006|pp=601–602}} The LAD returned only a small amount of useful data due to the failure of its power supply soon after activation.{{sfn|Harland 2011|p=325}} The LSM was deactivated on June 14, 1974, as was the other LSM deployed on the Moon, from Apollo 15. All powered ALSEP experiments that remained active were deactivated on September 30, 1977,{{sfn|Orloff & Harland 2006|pp=601–602}} principally because of budgetary constraints.<ref name = "astro">{{cite news|newspaper=[[Astronomy (magazine)|Astronomy]]|access-date=February 1, 2021|title=What did the Apollo astronauts leave behind?|date=June 21, 2019|last=Talcott|first=Richard|url=https://astronomy.com/news/2019/06/what-did-the-apollo-astronauts-leave-behind}}</ref>