Follow up to my previous question Third stage engine cutoff of Soyuz looks most intense, why is that?.

The third stage cutoff gives a pretty good kick to the cosmonauts, cued video at about T+ 08:46 during a Soyuz ascent. Is there any information about what G-forces the cosmonauts experience during this engine cutoff? Is there a way of determining how that compares to a 10 mph, 25 mph, or 40 mph head-on automobile collision?

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    $\begingroup$ Depends on what kind of car crash. $\endgroup$ Oct 28, 2019 at 14:17

1 Answer 1


3g (image below from this Quora answer), and it appears that the third stage cutoff is not the most intense. That one comes from the first stage cutoff, which is around 4g.

enter image description here

Car crashes can be huge g for small time, somewhere like 90+g, so not even close.

  • $\begingroup$ I'm under the impression the 3G figure has to do with the acceleration from the engines burning, when the cosmonauts are pressed back into their seats. The 3rd stage engine cutoff has the cosmonauts pushed forward into their restraints, their arms are thrown forward. The 90+G figure is for cars going faster than 70mph. I'm curious about lower speeds also, say 20 mph. $\endgroup$
    – Bob516
    Oct 28, 2019 at 14:13
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    $\begingroup$ @Bob516 see this question for info about the "throwing forward" part. space.stackexchange.com/q/35725/6944 $\endgroup$ Oct 28, 2019 at 14:19
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    $\begingroup$ Stage 1 to stage 2 is a drop from not quite 4G to just over 1G. Stage 3 cutoff is a drop from slightly over 3G to zero G. The starting force for first-stage cutoff may be higher, but third-stage cutoff drops further. $\endgroup$
    – Mark
    Oct 28, 2019 at 22:07
  • $\begingroup$ That cutoff-recoil phenomenon is, I think, the actual answer to the previous Soyuz 3rd stage cutoff question, but I have no way of quantifying it to answer this one. $\endgroup$ Nov 10, 2019 at 2:25

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