[ByronT]

I think it depends on the direction of the acceleration. The John Stapp experiment was horizontal acceleration, right? Right above that:

"... if g-forces are not quickly reduced, death can occur. Resistance to "negative" or "downward" g, which drives blood to the head, is much lower. This limit is typically in the −2 to −3 g (about −20 m/s² to −30 m/s²) range."

[damoncali]

I used to work at NASA on space shuttle launches. My boss at the time had an old (50's? 60's?) era book that detailed the testing on what acceleration would do to a monkey.

I felt bad for the monkey. But yes, direction matters.

[milkshakes]

relevant: https://en.wikipedia.org/wiki/Euthanasia_Coaster

[guard-of-terra]

Surprisingly it doesn't use reverse g "upwards" but rather an ordinary 10g "downwards". I wonder why is that and can't they make the system much smaller by aiming for the head.