Editing Apollo 14 (section)

=== Lunar orbit and descent ===
[[File:View of Antares from Kitty Hawk (14206333137).jpg|thumb|right|''Antares'' as seen from ''Kitty Hawk'']]
At 81:56:40.70 into the mission (February 4 at 1:59:43&nbsp;am EST; 06:59:43 UTC), the Service Propulsion System engine in the SM was fired for 370.84 seconds to send the craft into a lunar orbit with [[apocynthion]] of {{convert|169|nmi}} and [[pericynthion]] of {{convert|58.1|nmi}}. A second burn, at 86:10:52 mission time, sent the spacecraft into an orbit of {{convert|58.8|nmi}} by {{convert|9.1|nmi}}. This was done in preparation for the release of the LM ''Antares''. Apollo 14 was the first mission on which the CSM propelled the LM to the lower orbit—though Apollo 13 would have done so had the abort not already occurred. This was done to increase the amount of hover time available to the astronauts, a safety factor since Apollo 14 was to land in rough terrain.{{sfn|Orloff & Harland 2006|p=399}}

After separating from the command module in lunar orbit, the LM ''Antares'' had two serious problems. First, the LM computer began getting an ABORT signal from a faulty switch. NASA believed the computer might be getting erroneous readings like this if a tiny ball of solder had shaken loose and was floating between the switch and the contact, closing the circuit. The immediate solution&nbsp;– tapping on the panel next to the switch&nbsp;– did work briefly, but the circuit soon closed again. If the problem recurred after the descent engine fired, the computer would think the signal was real and would initiate an auto-abort, causing the [[Apollo Lunar Module#Ascent stage|ascent stage]] to separate from the [[Apollo Lunar Module#Descent stage|descent stage]] and climb back into orbit. NASA and the software teams at the [[Massachusetts Institute of Technology]] scrambled to find a solution. The software was hard-wired, preventing it from being updated from the ground. The fix made it appear to the system that an abort had already happened, and it would ignore incoming automated signals to abort. This would not prevent the astronauts from piloting the ship, though if an abort became necessary, they might have to initiate it manually.<ref>{{cite news |last1=Adler |first1=Doug |title=How an MIT computer scientist saved Apollo 14 |url=http://www.astronomy.com/news/2019/06/hacking-apollo-14-how-an-mit-computer-scientists-saved-a-lunar-landing |access-date=June 27, 2019 |work=Astronomy |publisher=Kalmbach Media |date=June 21, 2019}}</ref> Mitchell entered the changes with minutes to go until planned ignition.{{sfn|Chaikin 1995|pp=357–358}}

A second problem occurred during the powered descent, when the LM [[Doppler radar|landing radar]] failed to lock automatically onto the Moon's surface, depriving the navigation computer of vital information on the vehicle's altitude and vertical descent speed. After the astronauts cycled the landing radar breaker, the unit successfully acquired a signal near {{convert|22000|ft|m}}. Mission rules required an abort if the landing radar was out at  {{convert|10000|ft|m}}, though Shepard might have tried to land without it. With the landing radar, Shepard steered the LM to a landing which was the closest to the intended target of the six missions that landed on the Moon.{{sfn|Chaikin 1995|pp=358–359}}