# Re: starship-design: New discussion

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On Sat, 19 Jul 1997 15:38:09 -0500 "L. Parker" <lparker@cacaphony.net>
writes:
>-----Original Message-----
>From:	jimaclem@juno.com [SMTP:jimaclem@juno.com]
>Sent:	Friday, July 18, 1997 1:49 PM
>To:	starship-design@lists.uoregon.edu
>Subject:	starship-design: New discussion
>
>Okay,
>
>	Since my wild-haired ideas have been thoroughly picked at,
>I'll
>go to another subject, power for the Argosey, M.A.R.S. concepts.  It
>is
>stated in those documents that power on the order of 10^18 watts, or
>10^15 kilowatts will be required to drive a heavy sail-craft.  Here's
>an
>idea for getting that energy.  If you note the document on
>carbonaceous
>chondrite asteroids, you will find that those appear to have a
>silicate
>content of some 83 %.  If we mine these and use this material to build
>solar panels, LARGE panels, and place them orbiting the sun at about
>the
>orbit of Venus, we can get approximately 1 kilowatt for 3 m^2 of
>panel,
>assuming a final conversion rate of 10%.  Thus one square kilometer of
>panel will generate approximately 3 * 10^5 kilowatts.  Placing these
>at
>the distance of Mercury will generate some 9 * 10^5 kilowatts.  Lets
>assume that efficiency improvements will allow this to approximately
>double, giving some 2 * 10^6 kilowatts.  10^15 kilowatts now can be
>produced with some 1,000,000,000 square kilometers of panels, orbiting
>at
>the same distance as Mercury.  (Yep, those numbers seem to be right).
>This gives a disk some 36,000 kilometers in diameter!!!!!  Just trying
>to
>start a dialog on this problem, as this seems the best and quickest
>way
>to get probes out there.
>
>Jim Clem
>
>
>Jim,
>
>That is a pretty good idea. However as an engineer, I'm sure that you
>are familiar with conversion efficiency. Sometime ago I mentioned an
>old article I read on a solar powered laser that was based on
>principles of geometry - in other words it was mechanical, a trick of
>mirrors. I believe it was in Scientific American, but I'm not sure.
>(If anyone out there is near a library with archives, please look. I'm
>in a backwater here, the nearest decent library is almost a hundred
>miles.) Anyway, it would be very simple to set up mass production of
>such a device to kick out millions of these things automatically. The
>hardest part would be the control circuitry to keep them aimed at the
>same approximate point in space.
>
>Since it would be so low tech, we could send an advance probe to build
>an array at the other end to improve the flight times of subsequent
>colonization ships. Envision a small Starwisp type of probe with a ten
>pound payload of nanobots whose sole purpose would be to convert an
>asteroid belt into solar pumped lasers and control machinery. It might
>take it fifty years to get there and another fifty years to build the
>infrastructure, but after it was built we could put a M.A.R.S. or sail
>type ship up to near light speed quickly and then decelerate it at the
>other end without resorting to complicated magnetic loop braking, etc.
>
>L. Parker
>
You're right, I am familiar with conversion efficiency, pretty dismal
most of the time.  I'll check the pumped laser concept out.

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