Plumbing and Seals Between Rotating and Non-Rotating Station Modules.

[Spaceception]

I think this is worth its own topic,  I can put this in the questions thread if it isn't. But apparently (I can't find the exact source, other than the Apogee Space video which mentioned it), with the Commercial LEO Destinations program NASA is running to fund a successor to the ISS, one of the 'stretch goals' for contractors is adding artificial gravity. Now, I don't know if any are actually planning that (aside from outside companies like Vast Space), but I've been thinking over the last couple days, what they'll need if they do.

Some of the biggest concerns of weightlessness is bone density loss and muscle atrophy, so to counter it, Astronuats either need to exercise regularly, and missions can't last more than a year, or they need artificial gravity. We don't know how low is acceptable yet, or can at least mitigate health issues, but in either case, are there studies or plans on how to interface between a rotating and non rotating section? Not academic, but a Fn+F search on Atomic Rocket's section for artificial gravity didn't turn up anything either.

I'm also looking at it from the view of adding comfort and convenience for the Astronauts. It's not hard to imagine, that beyond crew quarters, a gym, rec area, and a low gravity research lab, there may  also be a kitchen/cafeteria, bathrooms, and showers. But then the question becomes, what happens to the gray/waste water? And how do you pump clean water back in? Rigid pipes are obviously out of the question, but would collection areas around the circumference of the non-rotating module work, funneling to several different pipes? After that though, how do you make sure the sealant is good enough to prevent cross contaimination? How do you access it for maintainence//cleaning/repair?

Would it be 'easier' to just use tanks that can be replaced every time they get full/emptied, carried in and out by Astronauts? Or don't bother with plumbing at all, and continue using zero-g toilets, showers, and kitchens?

 

Edited January 27 by Spaceception

[HebaruSan]

I'm sure some adaptations would be needed for space, but here's one way it's been done on Earth:

[kerbiloid]

The video sample rotates in the plane, perpendicular to the gravity axis.
They don't need to move their wastes up to the zero-g level.

***

CWR - centrifugal waste remover.

Everyone opens a hatch in the floor, and the wastes fly away.

***

The interesting part is the rotating part CoM balance, when they are walking around, or flushing the toilet.

[StrandedonEarth]

Perhaps the simplest, most foolproof way is to simply have the entire unit rotate, so no seals between moving parts are required. Docking would be at the axis, of course. Water would flow "down" to tanks in  the outer circumference where it would be filtered, cleaned, and purified, and could be pumped around to maintain balance, along with sleds loaded with other stores. Moving such a station could be problematic, however, especially re-orienting it. Perhaps it could be despun to make maneuvers easier, but that would require more features, valves, etc, to keep everything where it should be during weightless operations.

[darthgently]

52 minutes ago, StrandedonEarth said:

Perhaps the simplest, most foolproof way is to simply have the entire unit rotate, so no seals between moving parts are required. Docking would be at the axis, of course. Water would flow "down" to tanks in  the outer circumference where it would be filtered, cleaned, and purified, and could be pumped around to maintain balance, along with sleds loaded with other stores. Moving such a station could be problematic, however, especially re-orienting it. Perhaps it could be despun to make maneuvers easier, but that would require more features, valves, etc, to keep everything where it should be during weightless operations.

The angular momentum around the main axis should be fairly predictable.  Which thrusters fire to achieve a different orientation would be very unintuitive (helo pilot training would probably help some, ha ha). 

I imagine a better solution would be a computer controlled fly by wire attitude controller that dealt with the gyroscopic twistiness of it all and all the crew did was punch in the target attitude.

That said, attitude changes while rotating would be less efficient as the thrusters would be fighting the gyroscopic forces resisting a change in attitude

[Nuke]

if you want the compartmentalization benefits, you will probibly want every section to have its own independent life support, including toilets. the centrifuge itself might also be compartmentalized further for additional redundancy. however moving consumables like potable water and propellant around is probibly a matter of filling a tank and moving it through the airlock. the interchange becomes a very busy place as your crew size increases. 

for station design you can throw some serious machinery at the problem which would just not be in the mass budget for a space craft. i imagine big interchange rings, a small centrifuge, which can spin up, dock with the rotating section, exchange personnel and cargo, they can spin down for zero g access or even reverse direction if you got sections spinning both ways. bigger stations might actually have a rail system that can run through the hub. industrial stations will need a high throughput hub as some processes may be handled better under spin gravity than in zero g or vise versa. 

 

Edited January 28 by Nuke

[magnemoe]

On 1/26/2024 at 9:12 PM, StrandedonEarth said:

Perhaps the simplest, most foolproof way is to simply have the entire unit rotate, so no seals between moving parts are required. Docking would be at the axis, of course. Water would flow "down" to tanks in  the outer circumference where it would be filtered, cleaned, and purified, and could be pumped around to maintain balance, along with sleds loaded with other stores. Moving such a station could be problematic, however, especially re-orienting it. Perhaps it could be despun to make maneuvers easier, but that would require more features, valves, etc, to keep everything where it should be during weightless operations.

Agree, one smart idea might be to have an crane to berth ships and then move them to an docking port and stand inside an drum the crane would rotate to stand still relative to ship and get spun up for berthing. 
Problem solved, this will also settle liquid in the ships. 

If you only want to rotate part of the station I would go for an solution like the rotating house. I would even put an hole trough the center for non standard liquid by drawing an hose trough it. 
Hose would then have an rotating seal but that is pretty easy. 
An temporal setup is simplest, swing two arms so hose pass trough center. connect hose to freshwater inn and outtake, transfer water, repeat with grey water hose and connectors. 
I think you want to minimize water use in the zero-g part anyway so this might work well enough. 
 

[darthgently]

The artificial grav could be used for separation columns of fluids and such also.  A crane like magnemoe describes could be used to swap out the full tanks on the periphery for empties attaching the full product tanks where needed or into departing cargo craft.

In fact, magnemoe's crane could swap tanks for everything making no need for rotating plumbing at all on a separate rotating element.  Water, air, waste etc.

[Nuke]

On 1/26/2024 at 12:12 PM, darthgently said:

The angular momentum around the main axis should be fairly predictable.  Which thrusters fire to achieve a different orientation would be very unintuitive (helo pilot training would probably help some, ha ha). 

I imagine a better solution would be a computer controlled fly by wire attitude controller that dealt with the gyroscopic twistiness of it all and all the crew did was punch in the target attitude.

That said, attitude changes while rotating would be less efficient as the thrusters would be fighting the gyroscopic forces resisting a change in attitude

to pull "up" turn "right".

 

i think the thrust vector is the cross product of the thrust direction and the axis of rotation.  don't quote me on that though.

[magnemoe]

3 hours ago, darthgently said:

The artificial grav could be used for separation columns of fluids and such also.  A crane like magnemoe describes could be used to swap out the full tanks on the periphery for empties attaching the full product tanks where needed or into departing cargo craft.

In fact, magnemoe's crane could swap tanks for everything making no need for rotating plumbing at all on a separate rotating element.  Water, air, waste etc.

This was kind of my idea, Now I see it has issues especially if you are docking larger stuff say starship. Obviously the rotating ring would be hundreds of meter and you probably need to connect the arm on an truss so you catch and spin up ship and then move it down so if something goes wrong ship and ship releases it will not hit others or the station at least not until spun up 8 towers are also an overkill.