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Docking at a space station



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>Date: Fri, 4 Jun 93 06:51:37 -0500
>From: bjgaed@ccmail.monsanto.com
>Subject: Post to cherryhlist
Hi, all--

All this discussion of jump- and rocket-drives has brought up a problem that has puzzled me for a long time:
All indications are that ships in the Union/Alliance universe dock at the rim of a station. How does a ship maneuver to match spins with the station rim?

There is a sketchy description of this maneuver in _Chanur's Legacy_ where the _Legacy_, trying to avoid contact with station comp, matches spins and docks using ship comp and piloting, but details are lacking.

The physics of such a maneuver boggle my mind. How do you get a ship moving in a circle? To my mind you would need a tremendous amount of fuel to match the trajectory of the station rim.
Maybe you don't try to match the circular trajectory? Maybe you approach on a tangent vector that places you at zero relative V at the moment of closest approach and attach to docking grapples at that instant?

Can anyone describe to me how such a maneuver could be carried out?
Bruce Gaede


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>From: nancy ott <ott@ansoft.com>
>Subject: cherryhlist
>Date: Thu, 10 Jun 93 9:29:07 EDT
>(...)
> All indications are that ships in the Union/Alliance universe dock 
> at the rim of a station.  How does a ship maneuver to match spins 
> with the station rim?
And I always wondered how a station could keep a nice, even, 1-G rotation when a rather large ship like a carrier suddenly attaches itself to the rim. The really massive ships (like ore carriers) dock at the zero-G central axis of a station. But it seems to me that even a normal-sized ship would have enough mass to throw off the station's spin. (Think of how the small weights on an automobile tire affect the tire's balance.) And since the dockside is typically the level that's farthest from the axis of rotation, the effect of adding or subtracting this mass would be more pronounced.

"Downbelow Station" mentions a hydraulic system that compensates for this, but it seems to me there would still be some sort of disruption when a ship docks or takes off. After all, it would take time to slosh water around in tanks to compensate for the change in the station's moment of inertia. Perhaps the mass of most ships is small enough compared to the station's that ordinary dockings or undockings don't affect the rotation enough to be a problem....but a group of ships undocking at once would be a different story.
nancy ott (...)
ott@ansoft.com (...)

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