We all know the pictures of the astronauts on the ISS floating around. We also suspect that a lack of gravity is bad for the body as the muscles go weak and such.
Why don’t spaceships just rotate to cause the effect of artificial gravity through centrifugal forces?
For clarity: I don’t know for certain. I am not involved in the community, not an engineer.
Opinion: It’s incredibly difficult to do. A spinning station needs to be designed to do such a thing. It needs to be balanced and have thrusters positioned in such a way to both spin up and maintain the rotation as it goes. The ISS has been built and expanded over decades by tons of new science modules over time as new breakthroughs happened.
Spinning objects can behave in strange ways and having a regularly shifting center of mass can be a challenge by itself, and that’s before you start planning for yet uncertain experiments to bring aboard.
In addition to this, it would be an ENORMOUS challenge to dock with a station that is spinning, and the added danger to do this (or increased fuel consumption of spinning down and then spinning back up) just isn’t worth it. The alternative of maintaining a central core that is static relative to the spin wastes power and creates a massive risk (more moving parts, especially those which might create friction against metal aren’t easy to maintain in space).
Also, a small spinning station is much harder than a massive spinning station because it would have extremely noticeable differences from normal gravity to the people on board. Your head and feet would likely be moving at noticeably different speeds, which by itself is disorienting, but moving either towards or away from the direction of the spin would feel different (dropping an object would mean it falls away from the direction of spin).
Lastly, maintenance would mean that every single EVA either wastes a tremendous amount of fuel to spin down/up again, or risking flinging a person into space every time they exit.
Realistically, on a much larger station, artificial gravity via spinning might be a fantastic idea, especially for longer-term living aboard, but for the ISS, given its history, its goals, and especially where it’s at, it’s just not a great idea.
I think a flywheel mechanical energy storage system could both serve as a way to store energy and as a way to manipulate the rotation while preserving rotational energy. To slow down the rotation, transfer the rotational energy to a flywheel, and then transfer it back when you need to go back to speed. That adds some mechanical complexity but it creates a more efficient way to control rotation. Plus with electric motors and solar panels, that should be possible to manage without using any propellant fuel.
I wasn’t sure if a flywheel would be good for something like this given just how much mass needs to move and how fast it needs to move to produce close to 1G of force. If it can manage something like that, that would be a super good solve for this.
That said, even if it wasn’t a good solution for the actual ring, it might be a perfect solution for the core’s movement. Given that it can be much less mass as it’s pretty much exclusively used for docking, it could basically just be a pressurized tunnel with attachment points for the ring. Spinning that up and down with a flywheel seems super reasonable.
Could you not solve the spinning-ring-friction problem via magnets? The same way maglev trains work.
It doesn’t change that this isn’t really a great idea for the ISS, but that’s an obvious solution to the problem of having a static central core.
This is already quite a bit beyond where I have any definite knowledge, but I guess if you had a core completely separated by magnets that might work, but you’d still need points of connection for people who docked to join the actual ring from.
If you did that, the core would also need its own propulsion system to spin down and spin up so that anyone docking could actually go out into the ring.
It’s worth noting here, too, that the inner core would need to spin like crazy fast for a small station to have anywhere close to 1G in the ring, so that would be its own fun thing in the core.