The original note, as written at the time
The seats and cabins of space ships should be lined with considerably thick layers of memory foam to absorb the intense forces of rapid acceleration.
Ongoing development
The seats and cabins of spaceships should be lined with considerably thick layers of memory foam, to absorb the intense forces of rapid acceleration.
This sounds like a small furnishing note and it is actually a statement about what kills people in spaceflight. The forces are the danger, and the body’s tolerance depends almost entirely on how the load is distributed and how long it lasts.
Memory foam is the right material for the wrong reason and the right reason both. It conforms, so the load spreads across the whole body rather than concentrating at the shoulders and hips. And it deforms slowly, which means it absorbs a transient without bouncing the occupant back — the rebound being where a lot of injury actually happens.
The real requirement is support, though, and foam alone cannot provide it. Acceleration tolerance comes from immersion in a fluid, or from a couch shaped to the body so the load goes through the skeleton in the direction it is strongest — which for a human is chest to back. Foam is the comfort layer over a moulded structure.
The thicker point is that a cabin is a pressure vessel with a mass budget, and every kilogram of padding is a kilogram of payload. So the honest version is custom-moulded couches for the crew, thin, and generous foam only where the body is not supported by structure.
Design for the worst ninety seconds. Everything else in the mission is easier than those.