Re: Solar concentration mirrors in the outer solar system

From: WLM (wlm_at_post.com)
Date: 07/23/04 

Date: 23 Jul 2004 11:03:12 -0700

On Fri, 9 Jul 2004 10:59:36 +0000 (UTC),
     alexterrell@yahoo.com (Alex Terrell) wrote:
> The economics of far out settlements are a completely different
> subject. Suffice to say for the moment, that:
>
> - The masses are small compared to the settlement mass, upto the inner
> edge of the Oort cloud.

At 3 kw/per person, 1 Gw of power would serve the needs of 3.33 x 10^5
people. For a cylinder settlement of a million people at 100 square
meters per person density, I get a figure of 5.03 x 10^11 kg for the
total mass of the settlement. Using equations derived from the ones
in my original post, I get the following distances for each given
percentage of the mass of the mirror system compared to that of the
settlement:

Percentage Distance (A.U.)

1 1626
10 5144
25 8129
50 11502
100 16267

So for a mirror comparable in mass to that of the settlement, the
maximum distance is 16267 AU: a quarter of a light-year. The mirror
system's area would be 1.26 billion square kilometers.

> I suspect (using forseeable technology - which is not realistic) a
> large space settlement at 100 AU would use big mirrors for light, and
> nuclear power for electricity, with each able to back up the other.

I suspect that by that time they won't use mirrors, but instead will
build gigantic photovoltaic sheets. When they're able to manufacture
the thousands or millions of square kilometers of mirror cheaply, they
should be able to manufacture photovoltaic sheets not too much harder.

Photovoltaics would have lots of advantages over mirrors. The
problems of aiming the mirrors and keeping them relatively flat and the
support structure this requires is not needed. Instead a much lighter
tensional structure slowly spinning would be used just to keep the ***
more or less oriented to the sun.

Photovoltaics can probably be made out of the organic elements, more
common in the outer solar system than aluminum or other reflective
metals.

In the outer solar system where temperatures are near absolute zero the
photovoltaics might work much more efficiently.

At over 10000 AU the sun would be dim enough and the *** would be
big enough that light from starlight would become a factor. Put
photovoltaics on both sides of the *** and collect light from the
rest of the galaxy. Then don't even bother pointing it toward the
sun, point it toward the galactic center. Then there's no limit to
how far out from the sun the settlement can go.

-------
WLM

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