A torus space station is one of the staples of future thinking. Launching it in one piece from the ground is not. It has however, been occasionally mentioned in various comments. Here are a few numbers on the idea a few of us have kicked around from time to time.
Assume a 100 meter torus with a 10 meter minor diameter. 23,000 net cubic meters of internal volume should do for a start. A 50 meter radius that is not enough for an Earth gravity at under 4 rpm is sufficient for lower levels of artificial gravity that may mitigate some of microgravities’ harmful effects. It is getting it up there that seems to be a bit of a problem.
10,000 square meters of station surface would mass 540 tons if we assume the skin has the equivalent mass of 2 centimeters of aluminum including insulation, braces and such. Internal structure and furnishings would have to go up in subsequent flights. 540 tons in orbit would require something over 10,000 tons GLOW. This is heavy launcher country. Fortunately the internal volume of the torus is sufficient for fuel tanks.
Bladder fuel tanks inside the station could mass under half a percent of fuel mass, while LOX could be carried with simple bulkheads in the appropriate sections. Sooner or later an F1 equivalent will become operational at reasonable prices. 15 of them could push the torus edge on with a sled take off to avoid building launch towers and such. This would be a near SSTO with just engines dropped off for recovery at designated velocities when they are no longer required. Final push to LEO could be with just one engine with all the others recovered from various suborbital velocities.
How the station would be equipped and used would be up to the parties that paid for it.