Subject:
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Re: Where's all that gravity coming from?
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Newsgroups:
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lugnet.space
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Date:
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Sat, 10 Mar 2001 15:50:14 GMT
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Viewed:
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528 times
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In lugnet.space, Doug Dropeskey writes:
> As some people have already pointed out, you can rotate just about any
> structure for artificial gravity--a drum, a torus, a rectangular box, or a
> box at the end of a boom (with suitable counterweight). The problem with
> this methodology is the amount of gravity you will generate. Unless you put
> the rotated surface fairly far away from the center of rotation or spin the
> structure really fast, you won't get 1g. Fortunately, you can make do with
> a lot less (with some side effects).
As an example, if your structure is spinning at 2 rpm, you have to
go out to 225 mm from the spin axis to get 1 g. And you have to
be standing with your head towards the spin axis (like a hamster
in a wheel).
I got thinking about what this means for a space station. Assume
you have a station that has a long arm with a box on it (for the
people), and a counterweight on the opposite side of the spin
axis to keep it balanced. To dock a ship, ideally you'd like
to hook up where the gravity is, out on the box. This means
you need to spend fuel doing a "docking burn" to get into the
circular flight path you need to synchonize with the rotating
station. This should be done over a fair stretch of time to avoid
the instant onset of "gravity" I suppose. So you're burning
a lot of fuel, especially if it's a heavy ship.
Once the ship docks, if you shut down the thrusters, the ship's
mass is now being carried by the station, throwing it out of
balance. The counterweight on the opposite side of the spin
axis needs to move farther out to compensate. So there probably
needs to be a slow reduction in docking burn thrust while the
counterweight moves outward.
And your docking ring had better be strong, too, if you have a
heavy ship.
If the space station is circular, the counterweights could
be put on the spokes of the wheel. When a ship docks on the
ring, the counterweights move on the spokes as required,
all based on the masses of the ships, how many ships are
docked, where they're docked on the rim, etc. The balance
masses had better be pretty darn heavy!
Another idea might be to dock at the spin axis. No circular
docking flight path is required. Picture a coke can on the
spin axis, rotating with the station. When a ship is coming
to dock, motors start spinning the coke can opposite to the
station, so that to the people on the incoming ship the coke
can appears to stop spinning and become stationary. The
ship docks with the coke can, the people yank off the pull
tab and climb inside. The motors then allow the coke can
to start spinning again to synchronous with the station.
Once that happens, the people get out and begin to climb
out to the rim, experiencing a steady increase in "gravity"
on the way (thus they will probably be going "down" a ladder).
Some neat bearing connections could be made to keep from having
to spin up the docked ship along with the coke can. Due
to friction, anything attached to the spin axis will eventually
want to spin with the rest of the station. Small motors can
be used to keep the axis non-rotating. This would only be
needed while something was docked. Balance would need to
be addressed too, but much less so than for rim docking.
[Desperate attempt to stay "on-topic"] Anybody built
anything weird like this out of LEGO? How many things
went flying across the room? :]
KDJ
_______________________________________
LUGNETer #203, Windsor, Ontario, Canada
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Message has 1 Reply:
 | | Re: Where's all that gravity coming from?
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| (...) Better would be to spin the docking ship-- spinning the coke can the other direction means changing the rotational speed of the whole station. It'd me much cheaper to spin the docking ship, then you don't have to do anything weird at all on (...) (24 years ago, 10-Mar-01, to lugnet.space)
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Message is in Reply To:
| | Re: Where's all that gravity coming from?
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| As some people have already pointed out, you can rotate just about any structure for artificial gravity--a drum, a torus, a rectangular box, or a box at the end of a boom (with suitable counterweight). The problem with this methodology is the amount (...) (24 years ago, 7-Mar-01, to lugnet.space)
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