1. Uninflated gravity wheel |

The first figure shows the spacecraft system with an intermediate section that carries the uninflated gravity wheel. During the launch from the Earth the wheel is stored inside the rocket.

2. Partially inflated wheel |

The second figure shows the wheel partially opened. The wheel will be opened in the space where there is no atmosphere.

3. Fully inflated gravity wheel |

The third figure shows the wheel fully inflated. Once inflated the wheel will be filled with normal pressure air and the rotation started. First the rotation speed should imitate Earth gravity but it could be gradually slowed down to the Mars gravity to finally imitate Mars gravity when close to Mars. Astronauts should sleep and walk inside the rim to stay fit during the long mission (7 months to Mars).

24 m (79 ft) diameter inflatable gravity wheel |

The final figure shows the inflatable gravity wheel (IGW) dimensions and parts. Note that the center section allows the space craft not to rotate with the wheel. Inside the center hub there is a rotation elevator which makes the access to the wheel more convenient.

To generate Earth gravity in the wheel rim you need to turn it around about 8.6 times in a minute. The calculation can be done using the following equation. Notice that the gravity gradually increases from zero to full gravity when the person descends the ladder.

**a = v^2 / r**

where

**a = desired acceleration = g = 9.82 [m/s^2] (on the Earth)**

**v = rim speed**

**r = wheel radius = 12 [m]**

solving v we get:

**v = sqrt( g * r) = sqrt( 9.82 * 12 ) = 10.86 [m/s]**

Since the circumference k of the rim is

**k = 2 * pi * r = 2 * 3.14 * 12 = 75.4 [m]**

we finally get the required rotational speed w

**w = v / k = 10.86 / 75.4 = 0.144 [r/s] = 8.6 [r/min]**

If we want to create the Mars gravity on the rim we need to replace the g with the Mars gravitational acceleration, which is 3.711 m/s^2, and we get that the 24 m wheel should rotate 5.3 times in a minute.

In the following link you can find more about historic gravity wheels or rotating wheel space stations.

http://dodlithr.blogspot.fi/2013/10/rotating-wheel-space-stations.html

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