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?


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

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    $\begingroup$ 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 $\endgroup$
    – uhoh
    Mar 5 at 5:38
  • $\begingroup$ 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. space.stackexchange.com/questions/37762 $\endgroup$
    – Klaws
    Mar 5 at 10:25
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    $\begingroup$ @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. $\endgroup$ Mar 5 at 15:21

2 Answers 2


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.

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    $\begingroup$ 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 $\endgroup$
    – DonQuiKong
    Mar 2 at 20:52
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    $\begingroup$ @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! $\endgroup$ Mar 2 at 23:47
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    $\begingroup$ @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 :-(. . $\endgroup$ Mar 3 at 1:19
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    $\begingroup$ @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. $\endgroup$ Mar 3 at 6:29
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    $\begingroup$ 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. $\endgroup$ Mar 3 at 10:42

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.

  • $\begingroup$ 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? $\endgroup$ Mar 5 at 8:46
  • $\begingroup$ @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. $\endgroup$ Mar 5 at 12:12

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