asteroid habitats

--- In spacesettlers@yahoogroups.com, "Michael Capriola"
wrote:

> I've studied the concept of hollowing out an asteroid and converting
> it into a habiat. One of the plans suggested putting a parabolic
> reflector and a massive lens in the sunward pole of the axis in
> order to provide sunlight.

> My question is, is this the best way to provide light for a habitat
> roughly 30 km long? Is it even feasible?

Have you ever been in a modern day mine? Or seen pictures of the
insides of todays mines or even older mines?

Have you noticed all of the bracing?

The problems with hollowing out asteroids is that you're assuming
structural integrity. When you pressurize that asteroid you're going
to have a lot of tensile force exerted on bare rock walls, and this is
harder to compensate for than the bracing used for the compressive
forces in a mina.

Further, the remaining walls cannot safely be considered to be
monolithic, and in fact there may be sections that are loose
aglomerations, which would erupt when subjected to the forces within
atmospheric pressure.

If you have the technology to "melt" a whole asteroid, I'd simply
redeploy it so that you melt out the metals, then remelt the metals
into an engineered product - a Habitat shell.

As for your sunlight question well, let's work it through a bit.

You don't specify a diameter, so I'll assume 6 km. On the cylinder
wall, you've got 565 km^2 of area that needs to be lit. Assuming each
end cap is half of a sphere, the surface area of each end cap is 56.5
km^2. If one end cap is dedicated to your window, then you need to
light a total of 621 km^2 of area. Assuming you want to deliver 1,000
watts of light to each meter^2 of surface area you're going to have to
shine 621 GW through that end cap.

How will you create night and day?
How much heat will be absorbed into the endcap window?
How will the window radiate the heat?
How will you deal with the permanent shadows created by having the sun
be immobile in the endcap?
Will people like the effect of the sun being instantly "turned off"
when nightfall is reached and suddenly turned on at sunrise?
There will be a differential in light intensity between the region
immediately adjacent to the endcap window and the region 30 km away at
the other end of the cylinder.
Will people like to have their windows facing into perpetual shadow?
If you make the endcap window smaller, don't neglect the issue of the
amount of heat that'll be generated. If too small, the window material
might not be able to withstand the heat.

TangoMan