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This might be more of a physics question. If it is, I'll post it in the physics site.

If the spacecraft is vertical, wouldn't the astronauts be seated in a lying position so that the G forces do not cause blood to drain away from the head? Or, are the seats adjusted so that that astronauts can sit up like normal until it is time to launch?

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In all vertically-launching, crewed spacecraft I'm aware of, the crews are lying more or less on their backs on the launch pad, so G forces are transverse (chest-to-spine). This is the posture in which G-forces are best tolerated by humans. Films like The Right Stuff and Apollo 13 get this right.

In all the capsule-type craft (Mercury, Gemini, Apollo, Soyuz, Shenzhou), the reentry forces are the same way, as the capsule reenters backward.

In the space shuttle I believe the reentry is done nose-up, so the deceleration force should be pushing the astronauts downward in their seats and possibly slightly forward (maybe Organic Marble can correct me there).

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  • $\begingroup$ I've ridden in the Gravitron, where you start out standing on a forty-five-degree panel. As it spins, the vestibular senses tell you that you are shifting orientation, so that the new gravitational force is now making you feel like you're lying down. If I stood up on the wall, I would probably faint because there would be less oxygen flow to the brain. $\endgroup$ – HeavenlyHarmony Feb 21 '18 at 0:15
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Offered as a supplement - just to be totally clear, when the Shuttle was on the launch pad, the crew seats were in the same position relative to the vehicle as they were when the shuttle landed (except for a slight adjustment to seat back lean angle). So when seated for launch, the crew member was lying on their back with their thighs pointed up and their calves parallel to their backs. This was uncomfortable enough in the suits that Flight Rule A2-4 stated that they could only remain strapped in for 5 hours and 15 minutes prelaunch.

As Russell Borogove states, this seat position resulted in a more normal seating experience for entry and landing. The direction of the resultant acceleration vector varied somewhat but after the sensible drag started to build up it was always in the general direction of the floor. On the runway the Orbiter was pitched down a few degrees below the horizontal.

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  • $\begingroup$ I'm not super familiar with the Shuttle flight deck layout - how difficult is it to get the crew into those seats on the pad? Do they walk on the aft bulkhead toward their seat and climb into it, basically? $\endgroup$ – Russell Borogove Apr 11 '18 at 19:40
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    $\begingroup$ The side hatch opens into the mid-deck, below the flight deck. If you just stepped through the hatch, you'd fall into the toilet compartment. So that has a cover over it :) Once you have bypassed that, yeah, basically crouching down through the inter-deck access holes and climbing up with the use of foot-loops that get removed and the help of the cape crusaders in the white suits. Decent video here youtube.com/watch?v=1EOPPM5bfGc $\endgroup$ – Organic Marble Apr 11 '18 at 19:46
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    $\begingroup$ Here's a decent picture of the middeck popsci.com/sites/popsci.com/files/styles/1000_1x_/public/import/… That ladder wouldn't be there until the crew was strapped in. The top of the ladder is at the port inter-deck access hole. The big air duct is coming through the side hatch and the toilet compartment is behind the ladder. A webbing thing called the "trampoline" covers the indention that leads back to the external airlock. $\endgroup$ – Organic Marble Apr 11 '18 at 19:57

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