The Sword and Laser discussion

This is probably somewhat off topic but it is something that has bugged me since I watched The Martian and bugged me while I read Aurora.
I have a problem with the kind of rotating spaceships (as in Aurora) with a static central spine or hub and rotating habitat rings which provide gravity connected to the spine by spokes or arms.
It's all to do with the bearings or the connections between the rotating arms and the hub
The most fundamental requirement is that these bearings are low friction, so that you don't require too much energy to keep the rings spinning.
My problems arise because most depictions of this kind of spaceship have appear to be pressurised so there is a constant atmosphere between the arms and the hub. This is the case for the ship in Aurora and for this to work the bearings would also need to be airtight.
As far as I know there are 3 ways of producing a low friction bearing for stuff that rotates.
Magnets: Use two magnets with the same poles facing eachother so they maintain an airgap. This kind of bearing is used for flywheels and, on the same principle, for MagLev trains. The problem here is that it can never be airtight if there's an air gap.
Solid Lubricants. In space, rotating parts such as unfolding antennas or solar panels usually use a solid lubricant like Molydenum Disulphide(most commonly used I believe), Teflon or graphite for lubricating bearings. This kind of bearing wouldn't be (and are not meant to be) airtight.Also they reckon such lubricants last decades before wearing out and for the generation ship in Aurora it would need to last centuries.
Liquid/Grease Lubricants: You can produce an airtight seal for bearings with a liquid or grease lubricant (I'm fairly sure I've seen this done but can't remeber where) but you are going to run into difficulties if you have a pressure difference on either side of the seal. Also in the near vacuum of space with its attendant temperature fluctuations, liquids and greases have a tendency to evaporate, freeze or burn up.

If they used magnets or solid lubrication the ship in Aurora, they would probably need to keep the areas where the spokes joined the spine in vacuum. There would have to be airlocks between the spokes and the spine and at several places along the spine. If this was the case then KSR would have had to write a very different story.

Of course, if pressed, KSR would probably claim that they used some kind of "Super Space Grease" which provides both lubrication and an airtight seal but is only available in the 26th century.

The squeaky wheel gets the grease.

Just did a search. An early mention of the spine has the rings rotating around it, but a later mention has the struts connecting the inner ring locked at the spine, which implies the spine rotates as well. I suspect KSR meant it as the whole thing rotates in unison but was inexact in the earlier mention. Sort of like saying the spokes rotate around a central axis (he does refer to the spine as an axle, as well).

ETA: I'm assuming a fixed axle, not a rotating axle.