AT THE beginning of the space race, no one knew whether humans could cope with the fierce acceleration of launch and re-entry. So the successful voyage to the moon in 1969 had to be preceded by more than 10 years of preparation. I was in charge of some of the training, and much of this took place in a huge human centrifuge.
The machine was part of a flight simulation facility at the US Naval Air Development Center near Philadelphia, where I worked in the aerospace medical research department from 1958 to 1968. It consisted of a 15-metre arm with a cockpit at the end that could pitch and roll while the arm turned, and had been used to test flight suits worn by pilots to help them experience high g-forces without losing consiousness. We used it to simulate the stresses and vibrations that astronauts might encounter during launch or re-entry. We installed biomedical monitoring equipment to measure the physiological reactions and performance of the astronauts: the effects on their brains, hearts, circulation and muscle control.
It was up to me and others to test the equipment before we trained the astronauts. My wife was concerned that something might go wrong – which, of course, it did sometimes. Part of our task was to simulate what happened when something went wrong in the spacecraft, when an astronaut might have to escape or go to extremely high g. We took it up to 21 g for 5 seconds, which is very high.
Advertisement
What did it feel like? By around 6 g you start to lose your peripheral vision. Then you begin to feel a pain in your chest. Your circulatory system is altered at high g as the forces displace your heart within your body, and it becomes painful to use your feet or hands or even to move your head. It has been described as being like having an elephant sitting on your chest. Your body is under major stress, and the higher you go the more painful it becomes. At high g levels it is very difficult and painful, and the circulation throughout the body is affected. Even trying to move your fingers to turn a dial on the instrument panel is virtually impossible.
Afterwards, you feel dizzy and disoriented. It takes half an hour to recover. You may feel as if you are spinning, be unable to stand up straight or have trouble walking. It was surprising how much stress the body could take. We even tested people up to 32 g. For this the person was totally submerged in a capsule of water to distribute the force around the whole body.
The early space programme depended on the centrifuge facility, as it allowed everything to be tested in one place. It was used for the Mercury, Gemini and Apollo missions, and for the shuttle and the first space station. It was crucial to American space flight.
