Effective use of natural sunlight in a habitat.

On 7/26/07, joe@... wrote:
>
> And you've left out the most expensive part: we need to then reject
> (radiate) all the waste heat. Sunlight causes quite a lot of that;
> plants (for example) can use only a small part of the spectrum, and the
> rest gets converted to heat. Filtering isn't an answer, because most
> filters work by absorbing the unwanted frequencies, converting them to
> heat as well. Dichroic mirrors (which selectively reflect certain
> frequencies) are possible but quite expensive.

For agriculture, you could just pump algae through transparent tubes
_outside_ the habitat. That means the algae tubes double as both collectors
and heat radiators, for no extra cost, and they're not taking up
radiation-shielded 1g space that humans could have used.

Well, actually that's probably the second-most expensive part. A much
> worse (but harder to quantify) cost is all the design compromises you
> have to make in order to reflect or pipe light into a rotating habitat.
> (Though granted, if you don't restrict yourself to *imaging* optics,
> then this part gets quite a bit easier.)
>

And it gets much easier still if you only need the light for vision, not for
agriculture.