I had a back of the napkin design that was basically a sleeve that fitted over Starship and could be launched into orbit. Those sleeves had angled ends that could then be bolted together in orbit to make a station with an octagon shape that could be spun at 2 or 3 rpm to get 1/2 Earth gravity. Obviously still an enormous engineering challenge, but one that I think is solvable using today's tech. Well, tomorrows tech, but nothing that requires a breakthrough in materials science or basic physics or anything like that.
My plan was to fit the inside with huge water bags that would help to reduce cosmic radiation, provide thermal mass, and slow any micrometeorites that puncture the hull. The water could be launched on cheaper rockets and transferred in orbit. The water could also be pumped between sections to keep the wheel balanced. The central hub area would be more of a challenge, probably having to be assembled (or at least unfolded) in orbit.
Probably the biggest downside is that you wouldn't be able to spin it up until the entire structure was somewhat balanced, which means installing things like solar panels and radiators in pairs and the docking bit of the central hub would probably need to be on bearings so it can counter rotate to be effectively stationary or you wouldn't be able to dock more than 2 spacecraft at a time. The ISS was built in sections over the course of decades, this would need to be built all in one go, which is a huge commitment.
NASA's plans for two tethered stations (or one station and a counterweight) are probably more feasible, but much less cool.
My plan was to fit the inside with huge water bags that would help to reduce cosmic radiation, provide thermal mass, and slow any micrometeorites that puncture the hull. The water could be launched on cheaper rockets and transferred in orbit. The water could also be pumped between sections to keep the wheel balanced. The central hub area would be more of a challenge, probably having to be assembled (or at least unfolded) in orbit.
Probably the biggest downside is that you wouldn't be able to spin it up until the entire structure was somewhat balanced, which means installing things like solar panels and radiators in pairs and the docking bit of the central hub would probably need to be on bearings so it can counter rotate to be effectively stationary or you wouldn't be able to dock more than 2 spacecraft at a time. The ISS was built in sections over the course of decades, this would need to be built all in one go, which is a huge commitment.
NASA's plans for two tethered stations (or one station and a counterweight) are probably more feasible, but much less cool.