Pseudogravity

Rendering of Spaceship Hotel

Pseudogravity or artificial gravity is created with a rotational inertia force that mimics natural gravity. This is all together different from the force experienced by linear acceleration, the effects of which are indistinguishable from natural gravity, although linear acceleration is sometimes referred to as artificial gravity.

Gravity simulated by rotation or inertial force is one way astronauts can simulate extreme conditions. The prolonged weightlessness of space causes all sorts of adverse effects on the body, such as, motion sickness, bone density and muscle deterioration, internal fluid redistribution, and problems with intracranial pressure. Rotational artificial gravity has been suggested as a solution to these problems, however, currently there are no spacecraft outfitted to do this. Right now it seems infeasible to create a spacecraft large enough to create a centripetal force to approximate that of Earth’s gravitational field. There are also concerns about intolerable inner ear disturbances caused by the centripetal force, which would lead to nausea and disorientation.

There are a number of engineering problems with artificial gravity habitats in space, all of which would be soluble with enough resources, though none of which have yet been overcome. Artificial gravity has been achieved only at very low levels in space on purpose, through firing thrusters to rotate a craft slowly and carefully. The effects of this were not felt by the crew. On one mission an accidental continuous firing of one thruster caused a mission to be terminated, for the acceleration forces experienced by the crew were around 4 g. The most dangerous aspects of high forces of gravity experienced by humans are due to the movement of fluids in the body. Sustained high g force will cause blood to flow away from the brain, resulting in loss of consciousness and death.

There are a few differences in the behavior of artificial gravity compared to normal gravity in the context of a plausible habitat for humans. Standing on Earth one feels the same amount of real gravity pulling one’s head and feet toward the center of the planet. Centrifugal force, however, is directly proportional from the distance of the center of the hypothetical rotating space station. That means that with a small radius of rotation or a quick rotation, the amount of force felt at one’s head and one’s feet would be significantly different. Another issue is that linear velocity, for example jumping, within a rotating artificial gravity habitat is much higher than normal relative velocities.

Imagine a rotating space station large enough to hold a small community. The community is living on the inside of a ring, through artificial gravity, rotating through space. A significant issue with this hypothetical rotating space habitat is that moving in the direction of the rotation will increase the felt gravity, while moving in the opposite direction of the rotation will decrease the felt gravity. Humans moving towards or away from the axis of rotation in such an environment would experience the Coriolis effect, which causes dizziness, inner ear problems, nausea, and disorientation. It is unknown whether humans can adapt to long term exposure to the Coriolis effect at rates of over 2 rpm.

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