Artificial Gravity - Requirement For Gravity

Requirement For Gravity

Without g-force, space adaptation syndrome occurs in some humans and animals. Many adaptations occur over a few days, but over a long period of time bone density decreases, and some of this decrease may be permanent. The minimum g-force required to avoid bone loss is not known—nearly all current experience is with g-forces of 1 g (on the surface of the Earth) or 0 g in orbit. There has been insufficient time spent on the Moon to determine whether lunar gravity is sufficient.

A limited amount of experimentation has been done by Dr. Alfred Smith, of the University of California, with chickens, since they are bipeds, and mice experiencing high g-force over long periods in large centrifuges on the Earth.

Rats have been exposed to continuous artificial gravity of 1 g during Russian biosatellite missions lasting two weeks. The muscle and bone loss in these animals was found to be less than rats in 0 g. Astronauts were exposed to artificial gravity levels ranging from 0.2 to 1 g for a few minutes during several spaceflight missions, using linear sleds or rotating chairs. They did not perceive any changes in their spatial orientation when the g level was lower than 0.5 g at the inner ear level, where the sensory receptors for gravity perception are located.