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Rotating Habitat Modules - how do services connect ?


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So,  after spending a weekend on the totally awesome Atomic Rockets site 

http://www.projectrho.com/public_html/rocket/

I was thinking about an inner solar system passenger liner, working the routes between Earth,  Mars and the Asteroid Belt.

Near the front would be a rotating habitat cylinder.  Length greater than diameter because we don't want to jut out beyond the protection of the shadow shield from the engine section nor the whipple shield/forward fuel tanks from micrometeroids coming at us from the front.

The outermost decks of the rotating hab are going to have the most gravity and imagine you want the most gravity for 

1. Cardio Suite (gymnasium)  - a treadmill in low gravity is going to frustrate most users

Next - the Bathroom -  terrible things happen here in zero G.   As well as failure to achieve separation from things you very much want to be separated from,  there is also the issue of drowning while having a bath or shower which requires at least some gravity to mitigate. 

In the "some gravity is highly desirable" category you have the mess hall/restaurant   as well as the kitchen.    Your peas should stay on the plate, not float off, turn rotten,  then land in someone else's soup a week later.

However, a lot of people might prefer sleeping in very low/zero G and by no means all of the pressurized volume need be in the rotating hab.   

Which got me thinking - how would power, water,  and air be transferred from the rotating parts of the ship to the non-rotating parts ?  Is this an engineering problem that is already solved ?    Slip rings or wireless power transfer ?  What about fluids ?

I'm guessing there are automobile engineers with some experience handling similar problems..

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Power transfer is fairly trivial, sliding or rolling contacts should have no problem with this. Trains do it all the time.

Liquids (and non air gasses) are a bit tricky. Freely rotating fittings, aka rotary units, are available. If center of rotation needs to be clear of obstruction (at least occasionally) perhaps storage tanks on both sides and an automatic coupling / decoupling system?

Air goes through the same hole people do.

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19 hours ago, AeroGav said:

Is this an engineering problem that is already solved ? 

Yes. In the automotive world (where I work) there many different solutions that work well and could potentially be adapted. Thinking variable camshaft timing actuator and solenoid setup, similar to what @RCgothic said.

18 hours ago, Shpaget said:

Power transfer is fairly trivial, sliding or rolling contacts should have no problem with this.

Non-contact inductive power transfer could also work.

But, I do wonder, why rotate a piece of the ship? You could just make all the stuff fixed and rotate the whole thing. I would think a little gravity would help with things like fuel tanks and water recycling.

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3 minutes ago, AngrybobH said:

But, I do wonder, why rotate a piece of the ship? You could just make all the stuff fixed and rotate the whole thing. I would think a little gravity would help with things like fuel tanks and water recycling.

Science, recreation, communication (directional antennas), and, of course, docking.

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All those can be done with the ship rotating (sure it's more difficult). And wouldn't you have to stop rotating (the whole ship or the rotating assembly) for attitude adjustment prior to burning the engines because spinning things and gyroscopic forces?

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you have two concentric rings that fit inside one another (close but not touching), on the inside surface you have a groove. between the two you have something kind of like an oil seal in an engine. they are designed such that the oil pressure contributes a sealing force and usually made out of a material that contributes little friction to the rotating shaft. you can then attach fittings to the inside of one ring and the outside of the other. crew transfer can happen in the same way. id include a hatch at each end to minimize atmosphere loss and minimize cycling as much as possible.

a scaled up ship might have an interchange ring. a pressurized car that sits on a track and can "dock" with the rotating hab, or undock, spin down, and dock to the zero g section. this would be able to move crew and cargo, and might also contain small transfer tanks to move consumables around. this would have linkages that connect as part of the docking procedure. this is useful if you have counter-rotating ship sections.  

it might be easier just to have a small holding tanks in the hab and send a crewman to fetch a barrel every now and again.  this might be the budget option.  

1 hour ago, Shpaget said:

Science, recreation, communication (directional antennas), and, of course, docking.

i imagine putting the antennas, navigation equipment (inertial reference, cameras, scopes), etc in a small pod that rotates at the nose of the ship. this can also be fitted to an annular ring that surrounds the docking port or mounted further aft. this could be a bit larger if you needed solar arrays, but i figure if were talking centrifuge were probibly using nuclear engines or better. i dont think we will be able to manage anything other than a tumbling pigeon config with chemical engines, you just cant afford the superfluous mass. 

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9 hours ago, Nuke said:

i figure if were talking centrifuge were probibly using nuclear engines or better. i dont think we will be able to manage anything other than a tumbling pigeon config with chemical engines, you just cant afford the superfluous mass. 

A Mars cycler could be significantly bigger than bare bones, simce you only need to push it once. Once it's cycling you shuttle people and cargo on minimal crafts, but the cycler itself could be massive.

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7 hours ago, RCgothic said:

Note that transferring fluid out to a rotating ring will decelerate the ring due to conservation of angular momentum.

i figure just store fluid consumables in the centrifuge in the first place. you would need the ballast to keep it balanced. say you need your command staff to come to the bridge from their quarters across the ring, pulping fluid across to the other side would be needed to keep the ship from shaking apart. you don't want to put a lot of stress on a single precision spec'd component that is essential for connecting all the things. i suppose you could have a 2 hub system for stability and redundancy. but that's mass. 

if you wanted a zero g space as well, for things like cargo, dry consumables, rec area, rad shelter, etc, you could give it its own independent life support system. its nice to have extra redundancy for long haul missions. 

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1 hour ago, Nuke said:

i figure just store fluid consumables in the centrifuge in the first place. you would need the ballast to keep it balanced. say you need your command staff to come to the bridge from their quarters across the ring, pulping fluid across to the other side would be needed to keep the ship from shaking apart. you don't want to put a lot of stress on a single precision spec'd component that is essential for connecting all the things. i suppose you could have a 2 hub system for stability and redundancy. but that's mass. 

if you wanted a zero g space as well, for things like cargo, dry consumables, rec area, rad shelter, etc, you could give it its own independent life support system. its nice to have extra redundancy for long haul missions. 

Air is pretty trivial to transfer, simply make it double walled who you probably want to do anyway. pass air in through the double wall, you can have another for air out or simply use the passage. 
You outer rotating ring obviously need to be totally air thigh but the inner wall just need to be reasonable so, after passing the rotating joint you need an valve so you can shut off air and an airtight door You probably want one on each side for servicing. 

For water, I say water use will be in the rotating part as in drinking and washing water. Cooling water is different and not part of the life support system. solution is to put water recycling in the rotating part, it also easier to do. If you use water in the zero g lab bring an can. If you have two rotating parts have two water recycling systems who is something you want anyway. 
You could have an hose with an freely rotating join and set up an temporary water line say if one system is down. 

Rotating the ship would be easier, yes you might want freefall environments but here you counter rotate modules along the center line inside the pressure hull and only have to transfer power who you do with induction. Docking, you can dock at the front if you match rotation but this is more relevant for rotating space stations. 
Wonder if berthing is more practical for an huge station.  Grab ship and move it to an fitting docking port and support on an ring around the central arm. Perhaps have one central port for fast visits? 

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