How do you connect a spinning centrifuge to a non-rotating central collumn?

[K^2]

Now we could get into "why would you want hab space in a non-rotating section" part.

Because docking a ship to a rotating section is a) tricky and burns up quite a bit of fuel.

[Rune]

Because docking a ship to a rotating section is a) tricky and burns up quite a bit of fuel.

Without considering de-spinning the ship for that (in the context of near-term applications, the practical thing), there are a couple of ways of making it easier. First, you could try a tangent approach. That would require amazing precision and quite the quick and sturdy clamp mechanism, but it might be doable with computer assist with minimal fuel consumption (unless the docking changes the center of mass significantly for the target rotating ship). Or you could actually be smart about it and put the docking ports in line with the axis of rotation. Then it only needs to match rotating rates with the target ship, and you still have a microgravity slow-mo docking with minimal additional requirements.

Rune. KISS, an awesome acronym to engineer by.

[Nuke]

ive thought about this problem a lot. two things i notice:

you will probibly need 2 counter rotating rings keep the non rotating hull of the ship from spinning.

you dont need to have air tight connections between roating sections and non rotating sections.

the latter issue can be solved with an interchange ring. i actually drew this on a peice of paper lying on my desk

pretty cool. anyway one section rotates one way and the other deos likewise. in my design the sections are hung on rails, something like you would find on a roller coaster track, tubular steel with bering wheels on 3 sides. so they are independant pressurized compartments. in the center there is a track, with a pair of cars on a rotating frame. in its idle mode it is not rotating. if you want to go from one side to the other, the ring spins up with your current section, locks on to an airlock, you step in, then the ring slows down and begins spinning in the other direction to match the other rings rotation while lining up the airlock, then it docks with the other side. optionally the ring can also dock with a zero grav transfer tube that connects with the hub. i actully started modeling it as kind of a mod:

if iva ever becomes very robust, like allowing kerbals to float/walk on the inside, i might do a complete modeling of the interior, instead of just the bridge. for reference the bumpout windows are 1.25 kerbals high.

[K^2]

First, you could try a tangent approach.

That's mostly what I was talking about. It's basically landing to a hover. Except the docking ports are above you, you have no clear visual reference, there is no air to stabilize you, and you have a Coriolis force to worry about. Regular hover is one of the hardest flight skills to begin with. This would be way more challenging. Yes, instrumental approach is possible with computer guiding you in, but even that is far from trivial. They are just starting to do automated docking with none of these extra challenges.

And, of course, without a computer, you won't be able to get away with a short burn. Engines will have to effectively support the artificial weight of the ship while the pilot tries to dock. Having seen how long normal docking takes, that can't be cheap. And the cost of any mistake...

Tangential undocking would be fun though. Releasing the clamps and free falling into emptiness of space. Simple, efficient, breathtaking.

Or you could actually be smart about it and put the docking ports in line with the axis of rotation.

That's much easier, yes. And for small ships, it's probably the way to go. But for a large cargo ship, the centrifugal stress would be significant. Especially if the balance isn't quite right, which it won't be when you start moving cargo about.

Yes, for the smaller stations we will see in near future, these aren't real issues. But like you said, a small station you can just de-spin, resupply, and spin up again. Would make moving all the cargo that much easier, and you'd probably have to re-adjust the center of mass before re-spinning anyhow.

I'm talking about a bit further into the future, when you might have a large station in Mars' orbit, for example, and you want to get a year's worth of supplies delivered there in one go by a large interplanetary ship. One of these you definitely don't want to dock to anything that rotates. Of course, maybe the solution is not to dock at all, and to simply shuttle everything you need with smaller tugs. I honestly don't know which would be easier. But I really liked your spinning air lock solution. I think it might be the best way to go for something like this. It's basically the same shuttle and axial docking idea but running in a closed system. You can control everything with electromagnets saving tons on shuttle fuel.

[Rune]

Yeah, we seem to be reaching a consensus with that docking ring that spins and despins, and only mechanical connections the rest of the time. And the fact that the whole idea is for big ships. But I must confess, when I think about really large long-term stuff, I always picture O'Neill cylinders (or something very much like it). In those kind of huge structures, I imagine there would be an actual hangar in the middle. Perhaps not the whole lenght, but it could be hundreds of meters ling and wide in a structure measured in kilimeters. The ship would enter through the rotation axis, match rotation, and drop a few tens of meters to an extremely low gravity docking (the doors would be on the "ground"). Can't really beat a "no moving parts" system that only relies on the intrinsic huge nature of orbital colonies with artificial G.

Ships incapable of handling such maneuvers should actually never get close to large rotating structures that may collide with large relative velocities anyway... remember Tanya Kirbuk's misgivings to dock the Leonov with the unreliable Discovery in 2010? (the book, obviously) She was worried the centrifuge might fail and then the ships would destroy themselves absorbing the momentum. If so, they were all toast. So there would be tugs and shuttles to unload big transports, I imagine. The nice interesting deep space drives are usually too "hot" to bring close to habs and people anyway.

Another way of going about the problem entirely would be to have separate pressure and rotating hulls. Then you have air friction on your rotation, which means a bigger power draw, but the whole airlock business can remain separated and you minimize equipment in unpressurized areas. Actually, you could have the whole pressure hull and airlock spinning, and have a structure inside the airlock that you can spin-despin to dock ships. Definitely an idea for huge rotating habitats.

Rune. Wow, I was inspired there, I just meant to agree.

[Nuke]

i kinda like the way docking worked on babylon 5. seems once a ship is through the airlock, and before it makes contact with the station, its in a pressurized environment. just lock on to the elevator platform and get lowered down to the docking bay. seems they put a lot of effort into that design concept.

as for my ring concept up there, the idea is cargo would be kept in a pressurized zero g hold(which would be in the hub and adjacent modules, thats why its hollow), supplies are brought up the spoke tubes to the interchange car and into a rotating section as needed. since there are two interchange cars across from eachother you can load cargo through both of them at the same time (and you kinda need to in order to keep it balenced). all docking and cargo is handled on the zero g section. there really isnt any reason to bring a ship into a gravity section, especially if it isnt designed for it. and if you consider that supply ships possibly are robotic one off craft (essentially an engine and a guidance system attached to a crate), which would be totally disposable, or could be refueled and used for sample return (say rocks from titan).

you can loose pressure in any of the 3 pressure hulls and still have it in the other 2. in an emergency the crew can relocate to another compartment until the problem is fixed. the cool thing is you could vary the speed of the sections independently of each other to keep the ship torque neutral.

to optimize gravity stability, crew would reside in the ring that they work, and crew transfer between rings would be kept to a minimum, essential buisness only. to minimize that, and to also allow for some crew redundancy, each side would have its own cook and its own maintenance personel, its own engineer, its own doc, etc. the captain and xo would each be in charge of a section. crew and equipment movements would need to be actively tracked. things like the weight of the crew would need to be monitored all the time. crew gatherings would need to be limited (or limited to the zero-g section). storage space in the ring needs to be balanced out. in general a well disciplined crew would be neccisary.

the ring would then auto-balance itself by moving the water reserves around (and sometimes the crew would need to move stuff around as well). if the tanks are in the ceilings, walls and floor, then you get extra radiation absorption from those as well. of course for balence there needs to be some empty tanks to move liquid to when more ballast is needed.

the only real down side is it isnt really good for use on a ship with huge acceleration. i wouldn't want to use it for interstellar travel, you would need gimballed compartments for those kinds of accelerations. but my concept was to use mpd thrusters and a nuclear reactor, acceleration would be small and tolerable. i suppose you could use articulated floor plates which would change angle slightly, if more powerful engines were used. at zero thrust they would be flat (more or less), but with a lot of acceleration from engines it would rotate a few degrees so it would be like climbing stairs when you walk aft from one plate to another. this would probibly work fine up to 15-30 degrees or so, depending on the size of the plates.

Edited May 29, 2013 by Nuke