I was watching a tv series that showed an artificial ring around a planet. Although it was not clear if it was spinning or not, wikipedia suggests it would need to be spinning https://en.m.wikipedia.org/wiki/Orbital_ring
But if the ring is all around the planet, its centre of mass will coincide with the centre of mass of the planet, so it should be stable at any altitude even if geostationary (provided a proper material and the technology to build such a thing exists).
Am I right?
by jacoscar
2 Comments
Planets aren’t homogenous spheres, their gravitational fields are therefore “lumpy”. Furthermore, other massive bodies in the system will be exerting constantly changing gravitational torques on the ring (and the planet).
So no, there is no stable placement of a non-rotating ring around a planet.
Theroetically that would be correct, given the ring is strong enough to withstand all forces and will not drift in any way. You would need perfect equilibrium for it to work. As soon as one spaceship lands on it, the ring would be knocked out of equilibrium. Even the step of a human would be enough.
When the ring spins, it overcomes the gravitational forces by centrifugal forces, but will also act like a gyroscope in itself therefore being stable. As long as energy is being put into the spinning ring to keep it spinning, spaceships can land on it how much they want ant the ring will not be knocked out of balance just like the ISS.
I am no expert on this, but this is how I view it with the knowledge I have.