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We know from the answers to the question If a human is being sent to space in a rocket, does the seating angle matter? that seating position at launch is of less concern than landing. We also learn that some craft (Soyuz) have seats that change position between launch and landing.

What is the best (safest) position for a human at launch?

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  • $\begingroup$ Clarify: It is not unusual in Sci Fiction for older adults to migrate off of Earth to enjoy a longer life in low gravity (Space Station or Luna) with the intent of never returning to Earth. I am old and making a one way trip, I want the safest position at launch. $\endgroup$ – James Jenkins Nov 24 '17 at 18:41
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    $\begingroup$ What part of your question isn't addressed by the linked Q/A? The stresses at launch are lower, but they're in generally the same direction as landing; being flat on your back on a deeply padded couch would be slightly safer than seated-reclined, but requires more pressurized volume. $\endgroup$ – Russell Borogove Nov 24 '17 at 20:35
  • $\begingroup$ @RussellBorogove emergency escape acceleration can be substantially greater than launch acceleration. $\endgroup$ – uhoh Nov 25 '17 at 2:06
  • $\begingroup$ @RussellBorogove the linked Q/A is mostly focused on trained young healthy people undergoing less stress (3g) then the general public on an amusement park ride (6g) the answers there and (the one here so far) rely mostly on the Wikipedia article for reference. Where consideration for anyone not able take the strain in a sitting position is mostly ignored. This question is about when subtle differences matter, $\endgroup$ – James Jenkins Nov 25 '17 at 11:21
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Transverse forces supine +Gx "Lying on your back, Eye Balls In" Recommended high acceleration position

Transverse forces prone -Gx "Lying face down, Eye Balls Out" Second-best high acceleration position

Positive longitudinal +Gz "Sitting with head above heart, Eye Balls Up" Third-best high acceleration position

Negative longitudinal -Gz "Standing on your head, Eye Balls Down" Worst high acceleration position

Acceptable Acceleration Limits Yellow is seconds until unconsciousness, Orange is seconds of "tolerance" (whatever that means), Red is seconds until injury.

For example, an astronaut in the recommended +Gx lying on back position would have 5 seconds of consciousness at 14g, 5 seconds of tolerance at 27g and 10 seconds until injury at 48g.

Chart from a 1963 Douglas report

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    $\begingroup$ is that report available online somewhere? $\endgroup$ – Hobbes Dec 18 '17 at 9:23
  • $\begingroup$ Sadly, no. I got the chart from Scott Lowther, writer of the Aerospace Project Review. Contact him and see if he has a copy or will give out the title of the report. up-ship.com/blog/?p=5815 $\endgroup$ – Winchell Chung Dec 18 '17 at 20:17
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(Caveat: just googled stuff. Please correct me where I'm wrong.)

The direction in which the G-forces are applied matters:

(See also obligatory related XKCD/What If? link with a nice image) The Wikipedia article on G-force has some explanations on the effects to the human body depending on the direction. The human body is best able to tolerate acceleration "forward".

NASA has a short paper about the considerations for the seating but I didn't spot anything about the medical aspects of how the astronaut is seated (e.g. "lying" vs. "crouch"). Although current seats all position the astronaut in a slightly crouched position, it would be interesting whether lying straight might actually be preferable if you are only considering the launch and ignore the landing. However, I wasn't able to find anything about that topic.

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    $\begingroup$ It looks like this essentially says, the answer has not been researched.I wonder if the Russians did more research as Soyuz seems to taken more consideration about positioning then others. $\endgroup$ – James Jenkins Nov 25 '17 at 11:25
  • $\begingroup$ I don't understand the image. The different lines represent what? I see there's an inset but I can't figure it out. Possibly add a sentence? $\endgroup$ – uhoh Nov 26 '17 at 8:55
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    $\begingroup$ @uhoh The grey blob is a seated person, red is straight back, blue is straight up, green down, yellow is to either side. At least that is what it looks like to me after studying it for a while, and reading the wikipedia page linked in the answer, which is the image source. $\endgroup$ – James Jenkins Nov 28 '17 at 11:23
  • $\begingroup$ @JamesJenkins Ah yes, I see it now, thanks! $\endgroup$ – uhoh Nov 28 '17 at 11:26
  • $\begingroup$ Perhaps crouch (typical astronaut seating) is a compromise between highest tolerance (prone) and other factors such as layout/reachability of flight controls/instruments, spacecraft size/cross section, etc. $\endgroup$ – Anthony X Dec 18 '17 at 2:36

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