How does a spinning station work in reality?

[iDan122]

Firstly, on a stanford torus, there is a docking compartment which is connected to the main wheel via a hub and the docking compartment rotates in the opposite direction if that of the station at the same speed, so to a docking spacecraft the docking ports will remain still.

If we have one like in 2001 with a single docking port rotating on ts axis, then you just have to line up, make your rotation velocity match and dock!

If the port is on the exterior of the ring, then no way will you be able to dock to it...

[Nuke]

for very large rings id just use tangential approach and landing. for this you just have to aim for a landing platform hanging under the ring. your approach rate needs to be synchronized with the station, but your final approach speed is the same as the tangental velocity of the station. for touchdown you and the platform are roughly going the same speed, you just need to hold position over the pad for a bit until the floor rotates up and the stations artificial gravity takes over. the pad can also be retracted up into a hold and the doors closed, so you can step right off the ship into a pressurized, gravitized, environment.

Edited May 14, 2014 by Nuke

[Duxwing]

A docking port on ball bearings would remain almost stationary while the ship rotates and be easily stopped by the incoming docking port. After docking, crew would float into an axial tunnel and leap into branching tunnels to the ring. For a an axial tunnel of two meters' diameter and a ring rotating at 8rpm, the wall would hit the crew at

8 revolutions / minute * 2*~3.14 meters / revolution * 1 minute / 60 seconds

8 * 2*3.14 / 60 meters / second

~ 0.84 meters per second

Entering the station would resemble stepping onto a merry-go-round.

-Duxwing

[Opto Mist]

for very large rings id just use tangential approach and landing. for this you just have to aim for a landing platform hanging under the ring. your approach rate needs to be synchronized with the station, but your final approach speed is the same as the tangental velocity of the station. for touchdown you and the platform are roughly going the same speed, you just need to hold position over the pad for a bit until the floor rotates up and the stations artificial gravity takes over. the pad can also be retracted up into a hold and the doors closed, so you can step right off the ship into a pressurized, gravitized, environment.

Yeah, that's kinda what I was thinking... carefully timed/computer controlled approach at tangential speed, arrive just as the outer-ring landing platform rotates under you... smash that shuttle down on the deck and hook a tailhook to a arrestor cable just like on a carrier deck. Next a telescoping docking tunnel links to your shuttle door... pressurizes... passengers debark into a small atrium and take the elevator "up" into the main ring.

However--question: how does this affect the balance of the ring? You just added say 50 tons mass to the wheel in one location on the outer ring... though it brought along its own momentum at landing (near zero delta-v), does it cause the wheel as a whole to "wobble" or destabilize?

Of course, there could be huge reaction wheels on the station to compensate for imparted rotations due to shuttle arrivals and departures. But it gets complicated.

[Armchair Rocket Scientist]

for very large rings id just use tangential approach and landing. for this you just have to aim for a landing platform hanging under the ring. your approach rate needs to be synchronized with the station, but your final approach speed is the same as the tangental velocity of the station. for touchdown you and the platform are roughly going the same speed, you just need to hold position over the pad for a bit until the floor rotates up and the stations artificial gravity takes over. the pad can also be retracted up into a hold and the doors closed, so you can step right off the ship into a pressurized, gravitized, environment.

Another approach is to put a set of rails on the inward-facing surface of the ring. A docking ship approaches at very low velocity, lines itself up, and grabs the rails with some sort of clamp. A linear motor (aka magnetic catapult) in the rack then accelerates the ship up to the station's tangential speed - or, from the station's perspective, brakes the ship until it's stopped relative to the station. The ship can then be transferred to a series of docking ports off to the side, allowing another ship to use the same "runway." For departures, the process is reversed, with the same catapult accelerating the ship backwards until its velocity is zero, at which point the ship disengages its clamps and manuevers away in microgravity. Note that for a station with spokes, the docking ports themselves can be between the spokes, while the runways themselves can be off to the side, preventing a collision between a ship and a spoke.

For a "small" station of this type with a 1 km radius, the required tangential velocity is about 100 m/s, which is slow enough that the ships' clamping apparatus could be plain old wheels. For larger stations these could be replaced with a maglev system, but even with an immense 100 km radius ring, the tangential velocity is only 1 km/s. This is comparable to the speeds proposed for mass drivers used for launch into lunar orbit.

Note that this is primarily useful with very large space-based colonies where the mass of an incoming ship is negligible. Such a station could also use more conventional docking ports at its hub for very large spacecraft, but it could only have two of these - one on each side.

[Newt]

However--question: how does this affect the balance of the ring? You just added say 50 tons mass to the wheel in one location on the outer ring... though it brought along its own momentum at landing (near zero delta-v), does it cause the wheel as a whole to "wobble" or destabilize?

It would, definitely, but how bad it could be depends on how big the station is. If it is large enough relative to the ship, no one would notice. Otherwise you would have to do some work to counter balance the station.

Nasa Ames does an annual contest for space colony designs by middle and high school students. The vast majority use rotation, and a number of them talk about how docking and transfer would be achieved. The grand prize winners are posted here.

[Kerbart]

I think there are some logistical issues to fix with a rotating portion (ring/hammerhead/whatevah) on a space station.

• Air seal. Probably the toughest. Of course a labyrinth seal will get you there for a good part but inevitable you'll have leaks. Rubber sleeves or something like that? With the constant rubbing they will need fairly regular replacement, likely requiring the whole assembly to be stopped (and probably sealed off from the rest of the station).
  
• Air and other tubes. Probably the real challenge.
  
• Electrical connections. I'm sure that one is the easiest to solve but I have no experience with it.
  

The obvious conclusion would be to either have your entire station spinning as in 2001, with the ships entering the airlock through the central axis.

The other solution is to implement the centrifuge the way it was done on the Discovery (again, 2001) where the entire spinning construction in enclosed within the ship (or station).

The third is to have in independent non-spinning section on the station (connected through ball-bearings) that is entirely in vacuum thus not requiring difficult technical solutions. I'm pretty sure transfering crew from the docked ships to the atmospheric part of the station is possible without space suits although that would probably require a quite elaborate contraption.

[Bill Phil]

You could line up the rotation rates between the spacecraft.

Or, you could slow down a "hangar" from rotating, and then dock with it. then you could speed it back up.