From: gary@ke4zv.uucp (Gary Coffman)
Newsgroups: sci.space
Subject: Re: SPS feasibility (WAS: SPS fouling astronomy)
Date: 13 Aug 92 07:50:37 GMT
Reply-To: gary@ke4zv.UUCP (Gary Coffman)
Organization: Gannett Technologies Group

In article <10AUG199219061012@judy.uh.edu> seds%cspara.decnet@Fedex.Msfc.Nasa.Gov writes:
>In article <1992Aug10.004625.23290@dartvax.dartmouth.edu>, Frederick.A.Ringwald@dartmouth.edu (Frederick A. Ringwald) writes...
>> 
>>Again, WHAT reasons? Electric cars do not require SPS for their
>>development.
>
>No but converting a transportation infrastructure that runs on billions of
>gallons on Hydrocarbons per year to one of running on Terawatts of electricity
>will require a vast increase in electrical production. Where else are you
>going to get the energy in a non, polluting manner. The thermal pollution of
>SPS is miniscule compared to tradtional technologies.  Also the laser is tuned
>to a frequency that will not be absorbed by the atmosphere.

Let's look at this a bit closer with some ROM estimates. If we have a 1 TW
laser beam from the Moon impinging Earth, we add an additional TW to the
Earth's heat balance. Normal heat input from the Sun for the Earth is
about 140 TW so the additional 1 TW is less than a 1% change. But due to
efficiency factors discussed below, actual net heat load would be 3 TW.
By contrast, for Earth based solar collection, there is no net increase 
in heat flux. The energy is striking the planet anyway whether we use it 
or not. All of the energy eventually radiates back to space after being
used since any electrical equipment's energy usage ultimately degrades
back to heat. Note also that 1 TW of nuclear generated electricity also 
increases the heat load on the Earth by 3 TW, just like the laser system. 
Meanwhile, geothermal generation of 1 TW of electricity increases the heat 
load of the planet not at all, the heat's already here. So direct Earth 
based solar capture or geothermal are "free" energy while nuclear and Lunar 
Laser are sources of additional planetary heat. Plus, nuclear is cheaper 
than lunar, so if we're going to increase the heat load on the planet, we 
might as well do it with nuke plants.

Now what's happening on the Moon? Gas lasers are very inefficient devices. 
I don't have CO2 numbers at hand, but He-Ne efficiencies are around 0.1%. 
Giving an advanced CO2 laser a 10% efficiency is likely generous. Now to 
convert the IR back to electricity the Earth based receiver is either going 
to be photovoltaic cells, or some thermal system. In either case, efficiency 
is under 30%. That means that 34 TW of electricity has to be input to the laser 
on the Moon to deliver 1 TW at the power receiver busbar on Earth. Now the 
same efficiency factor is at work on the Moon as on Earth for converting 
light energy to electricity, so now we're talking around 100 TW of captured 
solar energy on the Moon for 1 TW delivered to the busbar on Earth. Note that 
I am totally neglecting transmission losses through the atmosphere of the 
laser beam. Now solar energy striking the top of the Earth's atmosphere, or 
the surface of the Moon, is 1 kW/m^2. So our 1 TW delivered to the busbar on 
Earth requires a solar collector area of 1E14 square meters on the Moon. That 
requires a square 10,000 km on a side, or about 6,000 miles on a side. Sorry 
gentlemen, the Moon isn't that big. Now if we discard the laser, the Moonbase 
with it's 6000 mile on a side collector, and simply use the same collector 
field we were going to use for the laser on Earth, we still gather in 1E10 
watts, or 10 GW, and we haven't spent an improbable fortune on the Moon.
Note that if we assume 100% laser efficiency, we are still talking about
a collector field on the Moon of 1E13 square meters, or a square 3200 km
on a side. Still too big.

A Lunar collector array would be in darkness 2 weeks out of 4, so storage
for two weeks would be required on Earth. For an Earth based array, only
8 to 12 hours of storage would be required for a single site. Since all
of Earth uses, or wishes to use, power, multiple sites around the globe
make sense to reduce transmission losses. Therefore, at least half of
Earth's capture arrays would be in daylight at any given moment. That's
at least 7 times better than the Loony Laser.

>>> All development of solar tech in the U.S. is carried out by SDIO and they 
>>> just got their throat cut by congress critters pushing bread and circuses 
>>> at the expense of the future.
>> 
>>Did you say all? This is news to me.
>> 
>Too bad you don't read the news.  There is some work being done by Sharp of 
>Japan on BSFR enhanced silicon cells. They are the only ones outside of SDIO
>doing any meaningful work.  Here is a list of the developments and the sponsors
>
>AlGaAs/CuInSe2 thin film tandem cells [Boeing Defense & Space & Kopin Corp]
>GaAs/Ge tandem cells [TRW]
>Amorphus (sp) silicon cells [sponsored by Larry Labs]
>
>There is no other development except a little by TI that I read about recently.
>The first two above are high efficiency cells (over 22% with Boeing up to 37%
>for the concentrators and 26% on Planar) For more information here I suggest
>you read my and my partner's paper on the SEDSAT 1 advanced power system 
>technology demonstration satellite from last year's Small Sat Conference.

I'm sure SERI, EPRI, and Arco, just to name three *US* solar research 
activities, will be amazed to learn that only Star Wars is doing research 
on solar energy. SoCal Edison seems to think solar generated electricity
is profitable *now* on Earth since they're building a plant. Luz was 
*almost* profitable at today's peaking prices. Most of the necessary
research has already been done, everybody is just sitting back waiting
for the price of fossil fuels to rise a bit before making large commitments
to *proven* solar technologies. Photovoltaic cells are not the *best*
way to use solar energy, and likely never will be for large scale power.
But solar *thermal* is workable *today* in certain cases.

>>> No we say that we must finally open up the last frontier to development. No 
>>> single technology or service from space will justify the expense BUT, taken
>>> together, the development of the resources of the solar system, whether it 
>>> be solar energy from space, materials from the Moon, asteroids, and other 
>>> planets will raise the planetary standard of living to a height that will 
>>> make today look like the abode of dirt dwellers.

So we lose money on every sale, but we make it up in volume?
Baahaaahahahahah.

>>What does this mean? It has a religious ring to it. Energy might work
>>(the point of this thread is to find out), but why should we want to
>>import bulk material from space to Earth? Few extraterrestrial ores
>>match the quality of those found on Earth, save for iron-nickel
>>asteroids, and there's already plenty of steel in landfills. Even if
>>you could import diamonds from the Moon, gold from the asteroids, or
>>star sapphires from Mars, could you beat the transportation costs?
>>Lunar chromium doesn't seem inviting. He3 remains speculative, much
>>more so than SPS. And there is NO market for lunar oxygen on Earth.
>>There might be one in space, but this seems like a circular argument:
>>there isn't, if there's no *other* reason to go into space.
>
>This is a flame and meant to be a flame. If you are so stupid that you do not
>know what this means why don't you pull your head out of the sand and read the
>papers. The Rio summit endorsed only ONE space technology and that was laser
>power beaming from the moon. In case you have not read we are running out of
>almost all of the easily obtainable minerals here on Earth. Don't quote me 
>your stupid statistics about percentages in the earth's crust. i know them
>as well as you. What you do not seem to see is that to get at those percentages
>we would have to pollute the world to an extrem extent just to keep up with
>preseent growth in the second world, not to mention the development of the 
>third world's standard of living. They want cars and computers and bridges 
>just like you in your comfortable American world.  There is a great big
>world out there, wake up to it.

To say that the political posturing in Rio was due to a lot of people
with their head up their ass would be understatement. As Paul Dietz
has shown at length, we are not running out of *any* material that
we need for advanced civilization with the exception of fossil fuels.
And there are ample replacements for them. The Earth is a closed system
except for energy, and even there natural sources are sufficient for
a population ten times the present size *indefinitely*. We have to work
smarter, not harder, to utilize those resources well. Raping the planet
depends solely on our stupidity, or lack thereof, space based materials
won't make a significant difference unless we stupidly continue to be
wastrels, and if we do, they're not going to help long anyway.

>>> This will allow the
>>> Ethopians, our perennial starving masses to irrigate there land and finally
>>> grow enough food to be taken off the planetary welfare roll
>> 
>>This assumes an end to the civil war there, which is largely an ethnic
>>conflict. If you can get these people to stop hating each other and
>>peacefully coexist, more power to you.
>
>Abraham Maslow in his text on psychology identified a heirarchy of wants and
>needs. Formost among them is food and shelter.  That is the underlying cause
>of the war in Ethopia at this moment.  The struggle just happens to be 
>tribaly not ethnically. Eritrian separtist movement is a tribal movement and
>so are most of the rest in Africa. Food comes before race and you protect your
>family (tribe) first. 

I think you might want to take a closer look at the underlying causes
of the Ethiopian civil war. It's not lack of food or shelter, it's 
politics at it's most base, like most wars. Like the people of Bosnia,
Ethiopians are quite capable of feeding and housing themselves when they
aren't being bombed and shelled off their lands. The current drought is
part of a cycle that has repeated for thousands of years. In peacetime
the people have coped with this by storing food from the good years to
carry them through the bad. The war has destroyed those traditional
practices, and prevented the humanitarian aid that is rotting on the
docks from being delivered to the people. THIS IS NOT A RESOURCE ISSUE.

>The SPS will help those who want to be helped. It can be used to rasie our
>standared of living without the destructiveness of raping the resources of the
>Earth. I propose that it is wise in your own conceit people like yourself that
>throughout history have played the role of opposition to the future by 
>ridiculing the Columbus's, and Wrights and Goddards and VonBrauns of the world.
>
>Part of religion is passion and yes I have a passion for the exploration and
>development of space, not for the sake of that exploration and development
>as and end in and of it self, but for the betterment of the lives of us 
>all here on earth.  I sure as heck have not seen your name associated with
>anything doing that.
>
>I don't usually go this orbital on a post like that but somtimes the arrogance
>and presumption of the poster just begs for it.

Sorry Dennis, I support space exploration and space exploitation too, but
I am realistic enough to know it won't make a material difference here on
Earth. Like Columbus' "discovery" of the New World, the riches ultimately 
fall to the inhabitants of the New World, not those left behind in the Old 
World. So it is with space. People living in space will be the primary 
beneficiaries of space activity. Earth can attempt to play Hudson Bay
Company, but eventually Earth has to manage by itself. I don't have a 
problem with that as a justification for supporting space. "To boldly go..." 
is sufficient reason to support space activities. The human race, wherever
they may be, will be the beneficiaries of that process, not Earthlings.

Gary