I think the limitations to radius set by material strength only apply directly to a cylinder spinning by itself without an outer support structure. For example, I think a rotating cylinder habitat surrounded by giant ball bearings connecting it to a non-rotating outer shell can use that outer shell as a foundation, so each part of the cylinder that is “suspended” between two adjacent ball bearings is like a suspension bridge of that length, rather than the whole thing being like a suspension bridge of length equal to the total cylinder diameter. Obviously you would need really smooth, low-friction bearings for this to be a plan to consider, although they would also help with wobble. One way of reducing the friction would be a Russian doll configuration of nested cylinders where each one out was rotating less fast than the previous, which (along with bearings etc) could maybe work.
On a similar vein, you could replace the mechanical bearings with a gas or fluid, in which the cylinder is immersed. Similar advantages in damping the wobble modes and (for fluids or very high pressure gases) helping support the cylinder against its own centrifugal weight. The big downside again would be friction.
As a “physicist and dabbler in writing fantasy/science fiction” I assume you took the 10 seconds to do the calculation and found that a 1km radius cylinder would have ~100 kW of losses per person from roller bearings supporting it, for the mass per person of the ISS. But I guess I don’t understand how you expect to generate that power or dissipate that heat.
I think the limitations to radius set by material strength only apply directly to a cylinder spinning by itself without an outer support structure. For example, I think a rotating cylinder habitat surrounded by giant ball bearings connecting it to a non-rotating outer shell can use that outer shell as a foundation, so each part of the cylinder that is “suspended” between two adjacent ball bearings is like a suspension bridge of that length, rather than the whole thing being like a suspension bridge of length equal to the total cylinder diameter. Obviously you would need really smooth, low-friction bearings for this to be a plan to consider, although they would also help with wobble. One way of reducing the friction would be a Russian doll configuration of nested cylinders where each one out was rotating less fast than the previous, which (along with bearings etc) could maybe work.
On a similar vein, you could replace the mechanical bearings with a gas or fluid, in which the cylinder is immersed. Similar advantages in damping the wobble modes and (for fluids or very high pressure gases) helping support the cylinder against its own centrifugal weight. The big downside again would be friction.
As a “physicist and dabbler in writing fantasy/science fiction” I assume you took the 10 seconds to do the calculation and found that a 1km radius cylinder would have ~100 kW of losses per person from roller bearings supporting it, for the mass per person of the ISS. But I guess I don’t understand how you expect to generate that power or dissipate that heat.