My current movie bugbear: Non-rotating with a large rotating section for the human habitat. Bonus points if the habitable part spans both the rotating and non-rotating portions and the crew can move freely between them.

It's an absurdly complex challenge to build it this way, it introduces an open set of failure modes that would not otherwise exist and there's no good reason for any of it that I can think of.

Instead, rotate the whole ship, and if there are a few things which for some reason must not be rotated (scopes, antennae and cameras, perhaps?) place them in the smallest and simplest possible unpressurised nonrotating segment at the axis.


Agreed. Stationary core and rotating ring is insanity.

Bridging the rotating/ non-rotating interface with power cables is difficult (slip rings or a Canfield Joint).
Bridging the interface with sewage lines is freaking impossible.

Just spin the entire ship already.

@nyrath @pieist Stationary core and rotating ring was the defacto standard for comm sats (particularly from Hughes) for many decades. The electronics and antennas were on a despun core, surrounded by a rotating "drum" that provided solar power, thermal regulation, and stability as a giant flywheel.

You'd never build a satellite like that today, but it was a very clever and robust design for the time.

@simonbp @nyrath Awesome. Thanks for that. The biggest part of my complaint-slash-incredulity is to do with the transfer couplings that have to retain atmosphere, resist torsional strain, be low friction and reliable. Not a job I would even want as an engineer. ("How about giving me a non-stupid problem to solve, please.")

No habitat involved in what you're talking about so it's mostly a "how much power and data complexity can we put into a coaxial link" problem.

@pieist @nyrath

The NASA Nautilus X ISS demonstrator was supposedly going to test that out, but they never got proper funding. It ended up being downscoped to the BEAM (non rotating) demonstrator, which launched shortly before Bigelow went under (but is still attached and functional on ISS).

@simonbp @pieist @nyrath Inverting things; the never-launched ISS Centrifuge Accommodations Module had a rotating core and a stationary shell. But that had the problem of the spinning section being entirely surrounded by air, increasing drag and angular momentum transfer to the shell.


@michael_w_busch @simonbp @nyrath

2001's Discovery was comparable: the spinning ring portion of the habitat was wholly enclosed within the pressure vessel. It solved a lot of problems re pressure couplings but yeah, you had friction losses and as you say, angular momentum to compensate for as a result.

While in principle you've reduced the complications to, say, putting a hamster wheel in an Apollo command module, you still had data and power transfer issues. And a f---load of mechanical load etc.

@pieist @simonbp @nyrath When I was involved with the Asteroid Redirect Mission proposal a decade ago; one variation was to have a non-spinning spacecraft surround a spinning asteroid without touching it, seal the bag, and then very slowly despin the thing by pumping in nitrogen to create air drag and transfer the angular momentum to the shell to be canceled by thrusters.

That was quite complicated enough.

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