The original note, as written at the time
It is crucial that only the living quarters and the control cabin spin. The supplies, engine and other support items do not spin. The spinning chamber can be resupplied by rail mounted drones. For this reason the diameter of the connecting axle tubing must be considerably large.
Ongoing development
Only the living quarters and the control cabin spin. Supplies, engine and support items do not. The spinning chamber is resupplied by rail-mounted drones, and for that reason the diameter of the connecting axle tubing must be considerably large.
The big axle is the idea, and it is the detail that makes the rest possible. The interface between a spinning habitat and a stationary service section is a bearing, and a bearing only works if there is something to pass through it — power, water, air, data, cargo, and occasionally a person.
Making that tube large is expensive and it is correct. A small axle means almost everything has to be transferred through slip rings and rotating couplings, which are the parts that fail. A large axle means the connections can be simple, accessible and, critically, serviceable — a person can go into the axle and work on it.
The rail-mounted drones are the elegant part of your design. Resupply that does not require stopping the rotation is the difference between a station that runs and one that pauses. A cargo drone running a circular rail inside the axle can move a pallet from the stationary side to the spinning side continuously.
The spin radius is then the constraint on the whole architecture: the habitat must be far enough out to give useful gravity, which sets the length of the axle, which sets the mass. Everything follows from the radius.
A habitat is mostly a bearing with a house on it. Design the bearing first.