# How realistic is a “bolas” system for artificial gravity in space travel?

The spinning space-station is very popular in sci-fi as a means of emulating gravity in space. But it requires rather a large diameter to minimise "gravitational gradient" effects and that means such a structure has to be large.

An alternative is two 'pods' with a rigid 'pole' which can be set spinning so that each pod has gravity for habitation while the pole is used for storage/etc. But even so, it's still a big structure.

So what about two pods tethered by a rope instead of a rigid strut? Suddenly the extra materials to get the whole thing spinning are quite small. Is this feasible or do the pods have to be connected by a rigid strut to stop them moving inwards or becoming erratic in movement?

• Moving inwards seems unlikely due to centrifugal-force. – Hennes Apr 27 '15 at 11:20
• might be even more fun to consider two very massive pods orbiting around each other under the force of gravity. Then you have no need for the rope at all :-) – levitopher Apr 27 '15 at 11:53
• Not very useful though. The question is whether you need a rigid connector to keep things stable, which to me seems a fair question of newtonian mechanics – Mr. Boy Apr 27 '15 at 16:01
• This is really a technology question. There would be no need to make the structure rigid since it will automatically rotate around its center of mass, but you don't want to make it large for reasons of efficiency. $F_{centripetal}=mv^2/r=2E_{kinetic}/r$. Therefor, to achieve constant centripetal force, the required kinetic energy in your pods grows proportionally with radius. Obviously the fuel requirements to spin the structure up and down are then roughly proportional to $\sqrt{r}$. It's not too bad, but fuel is expensive, so one would keep the radius as small as possible. – CuriousOne Apr 27 '15 at 21:57