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Did the Apollo mission have a contingency plan for the lander tipping over? For instance, would it have been possible for the two astronauts to somehow right it?

EDIT

This question is closely related and has lots of useful info: Did any of the Apollo lunar modules land significantly off level?

Steve Bennett
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    The lander was so heavy and squat that the troublesome lunar wind wasn't as much of an issue as it has been for the more recent landers – uhoh Mar 05 '24 at 05:38
  • You need pretty strong arms, even in lunar gravity to right the lander. So NASA did it the other way around and used Armstrong, to prevent the lander from toppling over. As the autopilot targeted a rocky landing zone (where the lander might have taken damage or tilted too much), Armstrong took over the controls and manually landed the lander at a different location. The lander was not supposed to be landed that way, and the landing was botched up - the landing was too soft and the lander legs didn't compress, so the ladder was way too short. https://space.stackexchange.com/questions/37762 – Klaws Mar 05 '24 at 10:25
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    @Klaws - actually all six of the commanders manually landed the LM. As Armstrong was taking over manual control at around 500 feet he noticed the boulders and so he reduced the horizontal deceleration so that they would continue farther downrange. The softer than usual landing had several factors, only one of which was that they were short on fuel because of the extension. There was also a slight horizontal drift which made Armstrong hesitant to shut off the engine. Also being the first landing, with a lot of unknowns, Armstrong later said he was already leaning towards making it more gentle. – Steve Pemberton Mar 05 '24 at 15:21

2 Answers2

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Automated hazard detection and avoidance remains a difficult and obviously not fully solved problem. The sole hazard detection and avoidance technique used with the Apollo mission was to have a human land the spacecraft.

Assuming almost all of the propellant on the descent stage had been used, the Apollo lander would have massed 2034 kg (dry weight of the descent stage) + 2445 kg (dry weight of the ascent stage) + 2376 kg (propellant mass of the ascent stage) = 6855 kg. At $1.62\,\text{m}/\text{s}^2$ (the gravitational acceleration on the surface of the Moon), that would have meant lifting over 11 kilonewtons (2500 pounds-force). Two people in balky spacesuits would not have been able to do that by themselves; they would have needed equipment that was not part of the manifest.

Besides, a tipover would probably have broken at least one lander leg, and Murphy's Law being what it is, would probably have tipped over so that the hatch was down.

Did the Apollo mission have a contingency plan for the lander tipping over?

Yes, they did. One of the many contingency plans was how to handle a tipover event. Uprighting the vehicle was not an option. The solution instead was to abort the landing. Unlike Intuitive Machine's vehicle, the Apollo missions were designed to return the crew to Earth. In the event of a tipover, the ascent vehicle would (with human intervention) have quickly separated from the descent vehicle and ascended. The initiation accommodated 1.4 seconds for pilot reaction time plus staging time delay plus thrust build-up time.

Organic Marble
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David Hammen
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    Imagine going to the moon for the first time and being trained for a number of contingencies to a level that you can react to a situation never ever having happened to any human within 1.4 seconds. Scary – DonQuiKong Mar 02 '24 at 20:52
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    @DonQuiKong More likely less than a second for human reaction and decision time. The 1.4 seconds included staging time delay and thruster build-up time. Scarier yet! – David Hammen Mar 02 '24 at 23:47
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    @DonQuiKong In a Robinson R22 helicopter you have 1.6 seconds after engine failure to lower the collective to allow the aircraft to enter autorotation mode. After that the rotors have lost too much energy and cannot maintain rotation from the passing airstream, and you die :-(. . – Russell McMahon Mar 03 '24 at 01:19
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    @DonQuiKong: true, but we are talking about some of the best test pilots, and an insane amount of specific training on top of that. And they had a big round "Abort" button to press in that case. – Martin Argerami Mar 03 '24 at 06:29
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    But imagine not being sure and having 1.4 seconds to decide whether you're going to the moon or someone else is under the threat of a slow suffocation death. I'd think that e.g. lowering the collective if the engine hasn't failed in the helicopter is irrelevant (?). If you abort the moon landing then you've aborted THE moon landing. – DonQuiKong Mar 03 '24 at 07:11
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    This seems to assume turning an object requires enough force to lift the object. This is not true, it's simply the upper bound for the complex field of "rolling stuff". I do agree with the conclusion though. – SE - stop firing the good guys Mar 03 '24 at 10:42
  • @SE-stopfiringthegoodguys With center of gravity in the middle and team astronaut working at the top end, the required forces would be halved - and still too heavy – Hagen von Eitzen Mar 03 '24 at 18:35
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    Just for clarification, the plan was to abort the landing if it seemed like they were going to tip, right? If the LM was actually on it's side, it must have been game over. – adam.baker Mar 04 '24 at 07:14
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    @adam.baker That's correct. The plan was to abort the landing if it appeared the vehicle was going to tip. Actually tipping over would indeed have been game over. Fortunately, that plan was never used, as were almost all of the many contingency plans. – David Hammen Mar 04 '24 at 08:12
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    @adam.baker I would hope that if things really went sideways and the LM landed on its side, they would have tried firing the ascent engine to see if it perhaps gets them off surface in one piece. There's no point waiting for the inevitable suffocation if there's something else you can try. Ground control would probably not have approved for bureaucratic reasons, but I guess the LM crew would just push the button anyway. – TooTea Mar 04 '24 at 10:05
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    If you're the kind of person, who always does the safe thing - you're not the kind of person who leaves the first steps on the moon. – Christian Mar 04 '24 at 12:35
  • @Christian That's exactly what "the right stuff" referred to. – Barmar Mar 04 '24 at 15:25
  • @TooTea once tipped over, the abort button would probably have become just a "faster death" button. I wager that if the crew had realised they were going to die anyway, they would have rather tried to get out on the lunar surface in person at least once rather than blow the chance there and then. – leftaroundabout Mar 05 '24 at 10:52
  • I wonder if using RCS would have helped at all with righting a tipped lander? I guess it also all would rely on the tipover being caused by some sort of dynamic event, rather than landing on a surface too steep to remain upright on. – Steve Bennett Mar 06 '24 at 23:31
  • @SteveBennett NASA had procedures for that contingency. See Russell Borogrove's answer to the question Did any of the Apollo lunar modules land significantly off level? In particular, see the last diagram in Russell's answer. – David Hammen Mar 07 '24 at 11:45
  • In particular, the attitude rate during landing had to be below a tolerable limit. Tipping too fast and too low would have been, as @leftaroundabout suggested, just a "faster death" than doing nothing at all (and dying slowly). – David Hammen Mar 07 '24 at 11:48
  • Yep thanks, I already linked to that one in the question. – Steve Bennett Mar 07 '24 at 21:56
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Well, the LM was 23 feet tall and weighed at least 2000 pounds in lunar gravity, once they used up all the landing fuel. (That's 7 m and 1 tonne, or, to be really precise, the force one tonne would exert on earth.) The legs were not meant for large lateral stresses. Even if the astronauts could lift the weight, they could not reach high enough to stand it up. Attempting to pull it up with ropes would be futile, since the astronauts would have even less traction than on earth, and one pair of legs would have to support all the weight plus some pulling stress at an angle they weren't designed for.

Mark Foskey
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  • Would they have had enough oxygen to dig a hole to (partially) right the LM? Or would a, say, 45 degree launch not work out? – Andrew Morton Mar 05 '24 at 08:46
  • @AndrewMorton Dig a hole in /what/? No two missions landed on terrain which was guaranteed the same, and the earliest manned missions still faced a great deal of uncertainly as to the load-supporting characteristics of the ground. – Mark Morgan Lloyd Mar 05 '24 at 12:12