Re: O'Neill habitat spin axis

From: EAC (digicross_at_hotmail.com)
Date: 08/26/04 

To: sci-space-tech@moderators.isc.org
Date:  25 Aug 2004 18:56:16 -0700

wallacethinmintr@eircom.net (Russell Wallace) wrote in message news:<412a03c1.116606037@news.eircom.net>...
> I'm designing an O'Neill habitat for use in a game scenario,
> where I'm trying to keep the science as plausible as possible.

Instead of saying "to keep the science as plausible as possible", it
might be better to say "to keep the science as low tech as possible
according to the scientific information that are released to the
public today".

> It's going to be the classic "spinning tin can" design,
> surrounded by an array of solar panels, mirrors and radiators

Well... I think that it would be much better and easier to use an
independent powerplant instead of solar panels and artificial
lightings instead of mirrors. But that's okay on using solar panels
and mirrors if you want it low tech.

It should be noted that there're some structural weakness in the
originial O'Neill designs, the movie "G-Saviour" feature some
refinements on the designs.

http://www.dyarstraights.com/msgundam/gsaviour.html

> (and directly in orbit around a star, rather than a planet,
> though I could change that if there was reason to do so).

Well... Putting it in orbit around a planet or near a planet might
make it easy for the people in the space colony to shuttle back and
forth from and to the planet.

Anyway. Since you're want to keep things as low tech as possible, it
might be better if these space colonies are built at the exact site
where the construction materials were gathered. Kinda like making a
brick house with the bricks were made from the soil next to the
construction site, or even constructing a house from a hilly land.
This method is easier rather than moving asteroids into prefered orbit
and then work on them, or even shuttling the materials from somekind
moon or asteroid.

For example, in Sun-Earth's L4 point and Sun-Earth's L5 point there
are plenty of asteroids trapped there, and these asteroids pretty much
stay there. These points with these asteroids should be good
construction sites, plus since that they are on the same orbit around
the star as the planet is, it would made shuttle flights between these
Lagrange points and the planet quite easy.

http://www.astro.uwo.ca/~wiegert/etrojans/etrojans.html

But then again, it might be scary if the Trojan asteroids are actually
more like the Trojan horse.

> My question is about the spin axis.
>
> I'd ideally like to point it at the sun. Then the nearside cap could
> be coated in solar cells while the rest of the surface is painted
> black to help radiate heat.
>
> But in that case, it seems that a quarter orbit later it'll be side on
> to the sun, another quarter orbit the opposite end will point at the
> sun etc, since conservation of angular momentum will tend to keep the
> spin axis pointing in the same direction relative to the rest of the
> universe, not relative to the sun.

The solution is easy to make it not pointing in the same direction all
the time, put another cylinder that rotate in the opposite direction,
that way the rotation of the two cylinders will cancel each other out.

http://lifesci3.arc.nasa.gov/SpaceSettlement/70sArt/AC75-1085.jpeg

Though there's still the matter of it keeping it aiming at the primary
star / sun, it will be a quite a hard thing to do.

For example, the Earth's Moon for example has the uncanny ability to
roughly keep the same face pointed at Earth, this and some other
things (like the moon distance was quite right enough to cause a solar
eclipse that almost totally covered the sun) lead some people to
believe that it might be a ancient space colony.

> Is there any way to change that (I mean, reasonable ways, i.e.
> without expending propellant or using huge gyroscopes etc)?

If you're talking about low tech ways, you will have more luck on a
spherical space colony than a cylindrical one.

Anyway. The current I.S.S. maintain its attitudes with gyroscopes, so
I guess that maybe putting huge gyroscopes should at least will fit in
nicely with the level of technology you're talking about. The whole
thing after all is already a huge gyroscope.

> Or if not, is the best solution then to orient it vertically, let most
> of the surface be mirror colored, and paint the end caps black?

Maybe the type of space colony below is much better suited:

http://spaceinfo.jaxa.jp/note/kouso/e/kou102_colony_e.html

> Thanks,

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