another dissapointment

Just noticed I made a typo in my last email, should have been a Brayton
engine,not Barton.
Coincidentally while googling for something I came across this, has
anybody by any chance read it ?

http://gltrs.grc.nasa.gov/cgi-bin/GLTRS/browse.pl?1992/E-7581.html

>
>>My dissapointment relates to two points which were not in the article.
>>1) the use of materials from the moon or asteroids to build the
>>satellites (as opposed to sending power from the moon) and
>>
>I mentioned Criswell - this is a way to lower the mass required to
>be launched from Earth (by sending manufacturing equipment instead of
>the final components). I think both options deserve study - unfortunately
>the NASA SSP group did ignore this, with the limited funding they had.
>
>I still haven't seen a concrete proposal for use of lunar or
>asteroid resources that allows a utility scale plant to be built (under
>$10 billion for several GW power). If you know of one I'd be very
>interested.
>

Concrete - no. only the info from The High Frontier, SSI and other bits
and pieces rehashed on the web.
hmm Criswell and power from the moon, I wonder if that website that
debunked this by saying the cables would get crossed is still up. lol.
Personal preference/bias, would much prefer to use moon material and
build satellites in orbit, than use ones based on the ground on the moon.

>>2) the use of Solar Thermal via mirrors and a Barton or Stirling engine,
>>as opposed to PV
>>
>I did mention PV in one spot, but mostly referred to generic
>"solar electric power systems"; again I think both deserve
>study, right now I believe solar thermal and PV systems are
>comparable in price for terrestrial use, but perhaps larger
>scale space systems would be quite different; I haven't
>seen mass per kW numbers for the thermal approaches either, so
>if you have references on that it would be useful.
>
Going from a very rusty memory from reading The High Frontier five years
ago (borrowed from the State Library) O'Neill leaned towards thermal (or
is my memory horribly mistaken?) over PV. (does my feeble memory
remember this quote correctly ? "Need more power ? build a bigger mirror")

I don't have any data on the relative pricing of PV and PT.

I do however have a link that some may find interesting, At the local
uni (Australian National University) they have a dedicated section for
solar power - both thermal and pv. ( http://solar.anu.edu.au/ )
as part of their work they have built what they call "The Big Dish" (
http://engnet.anu.edu.au/DEpeople/Keith.Lovegrove/STG/facilities.html )
which is a 400m^2 paraboloidal dish solar concentrator. The Big Dish is
meant to be just one of many in a larger plant, all feeding to a Thermal
engine. Unfortunately because it is built for use on the Earth's
surface, and because of the need to face directly at the sun, The whole
asssembly is rather heavy. The page lists 50 tons for the foundations
and 19 tons for the dish, though I am not sure which parts are
considered "dish" for the purposes of weight. It is quite impressive to
stand next to, though it really doesn't seem very big.

Consider however that PT basically consists of a mirror and the engine.
Consider also that later this year the planetary society will be
launching an inflatable mirror, that is 600m^2 in area, and weighs 100kg
into orbit ( http://www.planetary.org/solarsail/index2.html and
http://www.planetary.org/solarsail/missions/planetary_solar_sai.html )
Also note that last year (I think it was - or was it earlier this year)
NASA mentioned the idea of an inflatable station out towards the moon.

If - and a big If - you could build an inflatable Parabolic Dish shaped
mirror,(obviously larger than either 400m^2 or 600m^2 for that matter,
as you would need a lot more energy than that size system would supply)
using a similar material to that used on Cosmos, you could lower the
mass requirements for an SSPS significantly, which would leave the main
mass in the Thermal Engine and any support structure. Something to think
about at any rate.

>Thanks for the comments!
>
> Arthur
>
you're welcome :)

Brett