Before NASA was created, the US air force used its own men to test first hand the effects space travel would have on the body. The best way to do this was to strap a guy into a rocket sled to see how well the human body could stand up to 20~40gs. That is 20~40 times the natural force of gravity. The results were as promising as they were hilarious.
Instead of just firing people into space hoping for the best, scientists instead strapped willing subjects into a rocket powered sled called the "Bopper". Today there are high fitness and training standards to work in the field, but in the 50's all it took was a little insanity. This was new charted territory and no one had any idea what would happen to the human guinea pigs. If it were not for these tests mankind would never have reached space. Alton Yates, who worked under famous Colonel John Paul Stapp, proved that even in high tech fields all you really need are guts.