The sign by the couch. It read:
This Mercury couch was custom-made for Donald "Deke" Slayton to help hime cope
with the high-acceleration "g-forces" of riding missiles into space. The couch
prevents fainting by elevating the feet, keeping blood from leaving the head.
This is a training couch, not meant for flight. Slayton's flight couch stayed
earthbound because he was grounded by a minor heart defect. Slayton became
Chief Astronaut and finally reached space on the Apollo-Soyuz mission in 1975.
G forces were a problem not only during launch, but especially during reentry:
On the flight of Freedom 7,
for example, Shepard experienced 6 Gs during launch and nearly 12 Gs on