We have noticed that orbital space settlements are a rather unfamiliar concept for many people. In particular people find it hard to understand the meaning of land withing the context of a free space habitat. In this piece we will try to explain some of the essentials of orbital space settlements.

There are many proposed designs for rotating space habitats. The more well-known ones are the Bernal sphere, the Stanford torus and the O’Neill cylinder. What all these designs have in common, is that they have a circular cross-section of some kind. And hence we can draw a generalized diagram of a space habitat, as is shown below.

The circle represents the outer wall of a space habitat and this is what separates the interior – where people will live – from outer space. The wall is the habitat’s structure, without it simply cannot exist. So future spacers will be Trumpians in at least one sense.

In order to counteract the negative effects of weightlessness on the human body, gravity is replaced by centrifugation. By rotating around its axis – which passes perpendicular through the center of the circle – a so-called centrifugal force* is generated.

In a similar fashion as in a centrifuge or a washing machine, everything inside the habitat will be pushed to the wall. By choosing the right angular velocity the strength of this centrifugal force will be equal to Earth’s surface gravity.

So we can see that the part of the wall that is oriented inward serves a similar role as the surface of the Earth. Hence when we discuss land within the context of free space habitats, we usually refer to the inner side of the wall against which people are pushed onto as a result of the habitat’s rotation.

*Technically the centrifugal force is a fictitious rather than an actual force. But as one of my mechanics professors at college once said, a fictitious force can really kill you.

Further reading

Hyper Physics on Centrifugal force

National Space Society on orbital space settlements