Comic Discussion > QUESTIONABLE CONTENT
Spinning space station design
akronnick:
The counterweight module could carry all the heavy stuff like fuel, water, batteries and food. The habitation module could be relatively light weight, and doesn't need to be at 1g. In fact, if the station is being used as a way station between the Earth and the Moon, as in 2001, a lower gravity such as 1/3-1/2g may be more beneficial, as a transition for people who are adjusting between 1g and 1/6g.
pwhodges:
--- Quote from: Skewbrow on 20 Jan 2012, 03:15 ---How do you dock into the hub of a rotating space station, if you can't make the incoming spacecraft rotate at the same rate? At the hub you have control of the relative speed, but the rotation is still there.
--- End quote ---
I had thought about that; it seems to me that approaching along the axis and matching the rotations is trivial compared with having to accelerate continuously to keep in position during docking off-centre. I don't want to contemplate the other alternative of a stationary hub with the space station rotating around it!
--- Quote from: akronnick on 20 Jan 2012, 03:25 ---a lower gravity such as 1/3-1/2g may be more beneficial, as a transition for people who are adjusting between 1g and 1/6g.
--- End quote ---
But if they are not, and are only going between the station and the Earth, then what is the minimum gravity to avoid skeletal and muscular problems in the long term?
Skewbrow:
Paul, I can't do the mechanics right now. If coerced to do it I think I would be able to work out the tension on a catenary, i.e. a cable hanging from its end points at the top of the pylons with zero load, but the figures coming out would be meaningless for our present question, so I won't. Anyway, the angle makes a huge difference. May be the reason they want tall pylons is to increase the angle?
As an extremal case of a tiny angle consider the tension on the cable of a tight rope dancer. I may be way off, but I think it could easily be ten times the weight of the artist or more. IIRC in the story about the French guy who danced between the WTC towers they said that the tension on the cable was something like 5 ton(ne)s (sorry I don't know whether those were metric or not).
So the existing materials could be strong enough to take the tension of a spinning space station. If the spinning station has a full rim connected to the hub by several spokes, may be building a 'suspension bridge' from each and every spoke to the next one would give enough extra structural support?
akronnick:
--- Quote from: pwhodges on 20 Jan 2012, 03:36 ---But if they are not, and are only going between the station and the Earth, then what is the minimum gravity to avoid skeletal and muscular problems in the long term?
--- End quote ---
That's not really known. The only gravities humans have spent more than a few days at have been 1g and 0g.
We are adapted to 1g (obviously) and there have been Astronauts and Cocmonauts spending many months at a time at 0g since the 1970's, but the longest anyone has spent at an intermediate level was when Cernan and Schmidtt spent just over 3 days on the Moon.
Given that physically fit individuals can spend extended periods at 0g with little ill effect, artificial gravity on a spacecraft may be more of a luxury than a necessity (It does make filming Sci-fi movies simpler).
The real limit to long term space habitation is radiation exposure. Without the shielding properties of Earth's atmosphere, Astronauts in Low Earth Orbit receive much larger doses of some really scary photons.
pwhodges:
--- Quote from: Skewbrow on 20 Jan 2012, 03:52 ---Paul, I can't do the mechanics right now. If coerced to do it I think I would be able to work out the tension on a catenary, i.e. a cable hanging from its end points at the top of the pylons with zero load, but the figures coming out would be meaningless for our present question, so I won't. Anyway, the angle makes a huge difference. May be the reason they want tall pylons is to increase the angle?
--- End quote ---
A suspension bridge is not a simple catenary, though, because the deck is suspended from multiple points along the cable. The angles at the end are typically of the order of 45 degrees, so you don't have the tight-rope levels of multiplier (I start to see more extreme tensions when suspending microphones on a taut cable across an auditorium).
--- Quote from: akronnick on 20 Jan 2012, 03:56 ---The real limit to long term space habitation is radiation exposure. Without the shielding properties of Earth's atmosphere, Astronauts in Low Earth Orbit receive much larger doses of some really scary photons.
--- End quote ---
True - and the best form of shielding is (in effect) mass, and so impacts on the feasibility of our rotating designs.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version