high g body orientation

In article ,
Dumarest wrote:
is it better to orient someone, travelling at high g, perpendicular or
parallel to the line of acceleration (i.e. sitting/standing vs. lying
down vs. lying down but vertical)?

sci.space.tech is a better newsgroup for your question.
I've cross-posted there and redirected all followups there, so you'll
see replies to this article only if you read that newsgroup (or unless
someone replying changes the Newsgroups and Followup-to header lines
like I did).

I did a Google(TM)-brand Web search for
"high acceleration" posture
It finds few hits that are obviously helpful. The fourth hit was a
collection of e-mail and Usenet messages on G tolerance: "G tolerance
(Dani Eder; Henry Spencer; Jordin Kare; James Oberg)",
http://yarchive.net/space/science/g_tolerance.html. Mostly it's
about quantity and duration of acceleration, but there's a little on
postu

In article
(John Sotos) writes:

There are several points to be made about high G forces, blackouts,
neurological damage, and so forth.
...
The issue of "posture" is not a detail, it is critically important.
People blackout from G-forces when the acceleration is in the +Gz
direction (ie, blood is drawn out of the head toward the feet).
Pilots of high performance aircraft can usually tolerate about +9 Gz
with use of G-suits, straining maneuvers, etc....

Acceleration from front to back (+Gx) can be tolerated to a much
higher degree. Ham the chimp took +17 Gx during the launch of his
Mercury-Redstone flight and -14 Gx during re-entry. (The description
in The Right Stuff is a joy!) Apollo re-entries gave the astronauts
-7 Gx ("eyeballs out") or so.

As a lesser effect, I would also consider the load-bearing surface and
volume, though that's probably a lesser effect. If I were at 4 Gs, I
would weigh about half a ton. On my back, the load is distributed
(unevenly) across roughtly 860 square inches. Standing, it all lands
on my heels, about 50 square inches, through my leg bones.

Supine versus standing versus sitting are not the only choices. As
best I recall, a good one for 5ish Gs (?) is "seated on your back":
as if you sit down and then rotate the chair backwards 90 degrees.
Head and torso are horizontal, at the hips the legs bend upwards 90
degree vertical, at the knees the legs go horizontal again.

--
Tim McDaniel, ; is my work address