How long would it have taken to launch an Apollo contingency flight, if, for example, the lunar lander couldn't have got back up to orbit? Could the lander have held three astronauts?

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    $\begingroup$ The contingency case for failure to lift off from the moon was that the LM crew would die. $\endgroup$ Commented Jan 14, 2022 at 15:20
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    $\begingroup$ Obligatory xkcd: xkcd.com/1484 $\endgroup$
    – Kolmar
    Commented Jan 15, 2022 at 1:22
  • $\begingroup$ @Kolmar And on the more serious side, there is now a chilling simulation (starting at 3:35) of how the speech from the White House would have looked and sounded. $\endgroup$
    – nanoman
    Commented Jan 15, 2022 at 4:12
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    $\begingroup$ To back up Organic Marble, Richard Nixon had a speech ready to go in case the worst happened, which reiterates that fact $\endgroup$
    – Machavity
    Commented Jan 15, 2022 at 13:39
  • $\begingroup$ @nanoman Please take some time to consider whether that video really needs to be shared. Moon landing denier whack-a-mole is exhausting enough without the pointless distribution of manufactured lies. $\endgroup$ Commented Jan 16, 2022 at 9:13

2 Answers 2


How long would it take to launch an Apollo contingency flight, if, for example, the lunar lander couldn't get back up to orbit?

There was never a facility for contingency launches on the Apollo lunar missions. The LM's ascent engine simply had to work, or the astronauts on the lunar surface would die there.

All the Apollo launches were months apart. There were periods in which two boosters were at least partially assembled at the same time, but there was never a complete Saturn V ready for flight during another mission.

It might have been feasible to complete preparation for a launch in a matter of weeks instead of months, but the life support capability of the LM was measured in days, not weeks.

The Skylab missions in low Earth orbit did have contingency launch plans. Astronauts on Skylab could survive for months, so the timing wasn't as critical. The Command/Service Module of the rescue mission would have some storage lockers removed and additional couches added, launching with a crew of 2 and returning with 5.

Can the lander hold three astronauts?

The LM could hold three astronauts (and did, for much of the Apollo 13 flight). Getting all three aboard in full pressure suits with two of them using bulky PLSS backpacks would have been a challenge, but probably possible.

Landing the LM with a single crew member for a rescue would have been difficult and somewhat risky, but again, likely possible given the use of the "P65" automated landing program of the LM.

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    $\begingroup$ My understanding is if you had another Apollo ready to go on the launchpad it couldn't get there fast enough to rescue a stranded crew on the lunar surface. $\endgroup$
    – Joshua
    Commented Jan 15, 2022 at 5:19
  • $\begingroup$ @Joshua, that sounds plausible, but what is the LM endurance if the astronauts try to conserve energy and oxygen as much as possible? $\endgroup$
    – o.m.
    Commented Jan 15, 2022 at 7:12
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    $\begingroup$ @o.m.: By the time they try to start the ascent engine there's not a whole lot left. $\endgroup$
    – Joshua
    Commented Jan 15, 2022 at 16:40
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    $\begingroup$ @Joshua, you seem to assume that the crew detects the problem when they try to take off and fail. Worst case. I was assuming that something breaks on the landing and they notice immediately. $\endgroup$
    – o.m.
    Commented Jan 15, 2022 at 16:56
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    $\begingroup$ @o.m.: Full endurance is still only three days, and a launch window only comes every 23 hours and some odd minutes. That's already negative margin and may be impossible no matter how much you conserve. $\endgroup$
    – Joshua
    Commented Jan 15, 2022 at 16:59

Even if a Saturn would be ready at the launch site, it would have been impossible.

Each mission needed a specific version of the programs for the guidance computers of the LM and CM. Manual manufacture of the core rope memories took several months.

The software version for each mission was an individual design for the specific launch date and landing position of each mission.

  • $\begingroup$ Neil Armstrong was prepared to land the LM without terminal guidance. $\endgroup$
    – Joshua
    Commented Jan 15, 2022 at 16:55
  • $\begingroup$ @Joshua Armstrong did only the very last phase of the landing manually. But the computers were needed all the time from launch to this very last phase. $\endgroup$
    – Uwe
    Commented Jan 16, 2022 at 17:04
  • $\begingroup$ What he did do and what he was prepared to do were two different things. $\endgroup$
    – Joshua
    Commented Jan 16, 2022 at 17:37

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