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Assuming such a space station needed to have its central hub not used for docking spacecraft, would it be plausible for a spacecraft to dock on the outer edge of a rotating wheel if the ship approached the station on a tangent to the outer edge, in the direction of rotation? I'm assuming a drone ship, of equal mass, would simultaneously dock on the opposite side of the station to maintain the balance of the mass of the station.

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  • $\begingroup$ Why the drone ship? Are you thinking the station is like a centrifuge? $\endgroup$ – Willk May 29 at 2:41
  • $\begingroup$ @Willk Yes, I'm thinking of the station as a centrifuge. $\endgroup$ – Bob516 May 29 at 2:44
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    $\begingroup$ "Well, captain, we can go for the high-risk-of-catastrophic-failure-for-little-reward tangent dock. Or we can just dock easily and safely at the hub with everybody else. The ship owners and crew have entrusted you to complete our mission safely, on time, and on budget. What are your orders?" $\endgroup$ – user535733 May 29 at 2:53
  • $\begingroup$ This possibility and its drawbacks are covered in this more general question What is the best design for docking onto a rotating space-station?. Possible duplicate? $\endgroup$ – A Lambent Eye May 29 at 7:41
  • $\begingroup$ Seems like a lot of trouble to go to when you have a nearly infinite amount of hub you can build onto $\endgroup$ – John May 29 at 15:47
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Can you launch an ICBM horizontally?

Sure. Why would you want to? (The Hunt for Red October)

You absolutely can dock on the outer rim. It will be the biggest pain in the tuckus your pilots have ever seen, but yup, it can be done.

There are (at least) two reasons why the central hub is preferred.

  1. You only have to spin the ship on one axis, if you must spin it at all.

  2. You can design the hub so that the docking hub doesn't spin, which is even simpler.

But hitting a docking port on the outer rim means the ship must move on at least two axes. That's what it takes to move in an arc: two axes. This is because you can't actually move up to a point tangent on the outer rim and dock.

Why?

Because docking takes some time. Even if you're trying to capture the ship with some cool clamps. The ship is moving in one direction (a straight line) and the outer rim in another (an arc). The "docking time" isn't just a second... it's a minuscule fraction of a second — and if you don't get it right the first time, things (usually the ship) get ripped apart.

So, theoretically, yes, you can dock a ship via the outer rim. It's not recommended.

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    $\begingroup$ Given time, money and an unhealthy dose of masochism, everything is possible :D $\endgroup$ – Renan May 29 at 2:57
  • $\begingroup$ Could be doable if you had a docking bay that was a big scoop and you timed it juuuust right. Then all you’d have to worry about is slamming into the back wall of the docking bay! $\endgroup$ – Joe Bloggs May 29 at 10:11
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No

That would make no sense as it's too complicated and too many things would go wrong.

The station would have a self balancing system which would operate by pumping water to holding tanks around the rim.

As the ship docks, water would be pumped from the area where the ship was to the area opposite the ship.

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  • $\begingroup$ The ship docking will be instantaneous, but the water ballast transfer will take significant time. And during that ballast transfer the rotation of the station will be affected. Even if the station can withstand the stress, the inhabitants are going to be seasick every time a ship docks or undocks. $\endgroup$ – Ray Butterworth May 29 at 12:40
  • $\begingroup$ Can't possibly be instantaneous. The ship is going to have to match rotation using its own jets. It would taper off it's jets as the station corrects the imbalance. I'd also like to point out this is why you'd never dock on the outer ring of the station. It's the worst spot to dock. $\endgroup$ – Thorne May 29 at 23:07

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