If we would like SPS's to be implemented in the near term, they must have a
comparable price per KW for terrestrial based energy sources.

The cost per KW for an SPS is based on the cost of building and maintaining
the SPS and its efficiency in energy production, conversion, and
transmission.

Thus to bring the cost in line with terrestrial based we must either
substantially lower the cost of building and maintaining the SPS, or greatly
increase its efficiency.

For building we have a couple of different costs

1) Equipment/material costs
2) Launch/getting the materials to the proper orbit costs
3) Assembly costs
4) Maintenance and repair costs

1 is strongly related to efficiency - i.e. energy production per hour per
kilogram, so we'll delay discussing that until the efficiency section.
Another consideration is where the materials come from, using NEOs or the
Moon as the source of materials and manufacturing the finished materials in
space might substantially reduce the cost of the equipment.

2 currently their is a great deal of research on reducing launch costs. The
funding levels are currently fairly trivial. I would suspect that greatly
increasing the funding to launch research would easily pay for itself many
times over.

3 It seems that AI or teleoperation might offer the best chances for
significant reduction in assembly costs.

4 maintenance and repair are also excellent candidates for robotic
teleoperation.

Efficiency - we can use the conversion efficiencies from the SPS study they
were

Solar Distance .9675
Seasonal Variation .91
Solar Array .145
Array Power Distribution .937
Antenna Power Distribution .963
DC to RF 0.85
Antenna 0.98
Atmosphere 0.98
Energy Collection 0.88
RF to DC 0.89
Grid 0.97
The solar array is the area for biggest gains, however their are significant
gains that could be had in the energy conversion and collection. The
question is, how much of a theoretical gain can be had in each area, and how
much (and how expensive) the research would be to achieve those gains. We
could contact professors of EE who do research into microwaves and solar
energy and they might be able to give us a reasonable guesstimate. I'd bet
that a 1/4 billion in research money would easily drop the cost of KW/kg
enough that we could lop off 10s of billions off the final cost.

What is needed, is to find what the current cost estimates for each of the
areas is, and then see how much cost savings could be realized by the
proposed improvements.

Tom M.
TomM@...

>Efficiency - we can use the conversion efficiencies from the SPS
study they
>were

I am concerned that the numbers from this study have no basis. The
real-world numbers that I have been able to find on DC to RF to Antenna
are less than 50%. Perhaps the first goal would be to find actual
data to support or modify these numbers so that there is a clearer
starting point.

Mitchell James
mejames@...
http://www.InnerTransit.net (Email distribution for multilevel organizations)
http://www.InnerTransit.org (Homebase for collaborative engineering)

The numbers are from http://www.permanent.com/p-sps-tc.htm

which in turn based their numbers on the US DOE Solar Power Satellite
Concept Development and Evaluation Program (SPS CDEP), Final Report

If we can get ahold of the initial report, we can find out what the DOE
report based their numbers on.

Tom M.
TomM@...

>I am concerned that the numbers from this study have no basis. The
>real-world numbers that I have been able to find on DC to RF to Antenna
>are less than 50%. Perhaps the first goal would be to find actual
>data to support or modify these numbers so that there is a clearer
>starting point.

>Mitchell James
>mejames@...
>http://www.InnerTransit.net (Email distribution for multilevel
organizations)

Okay,

I found the below two links one from 1994 that gives a dc-to-rf of 73%, and
the other of 65%.

The primary author on both is (Daniel) D.E. Rees, who apparently works for
LANL and has the email address drees@...

He might also know where the DOE came up with their numbers.

So, I suggest that the next order of action would be to contact Mr. Rees and
see if he can provide additional information,

Tom M.
TomM@...

http://www.google.com/search?q=cache:4wfHz9bTpD4:web.nps.navy.mil/~library/b
ibs/dewtrs.htm+DC+to+RF+conversion+efficiency&hl=en

"Rees, D.E. "Models to Evaluate Magnicon Architectures and Designs Suitable
for High-Perveance Beams." Thesis (Ph.D.) Los Alamos National Laboratory,
NM. March 1994. 271p.
Abstract: The magnicon, a new high-power, radio frequency (rf) deflection-
modulated amplifier, was recently developed at the Institute for Nuclear
Physics in Novosibirsk, Russia. The first magnicon achieved a peak output
power of 2.6 MW for 50-(mu)s pulses at a frequency of 915 MHz with a
dc-to-rf conversion efficiency of 73%. The conversion efficiency achieved by
the original magnicon represents a significant improvement over
state-of-the-art conventional velocity- and density-modulated devices.
Therefore, if properly exploited, the magnicon could substantially reduce
the operating expenses of industrial, scientific, and military facilities
that require large amounts of RF power. This dissertation describes the
operational principles of the magnicon, provides small-signal analytical
theory (where practical), presents a large-signal numerical model to
characterize magnicon performance, and then utilizes this model to
investigate the characteristics of the component magnicon structures. Using
these modeling tools, the first-generation magnicon architecture is analyzed
for its performance sensitivity to electron-beam size and is found to
support beams of only limited diameter. Finally, an alternate magnicon
geometry, called a ''uniform-field'' magnicon, is presented and shown to
support beams of larger diameter.
ACCESSION NUMBER: DE-94-009370"

and from

http://www.google.com/search?q=cache:pohIKfJ0Szk:www.aps.anl.gov/conferences
/LINAC98/abstracts-M.html+DC+to+RF+conversion+efficiency&hl=en

MO4075
Accelerator Production of Tritium 700 MHz and 350 MHz Klystron Test Results*

D. REES, M. LYNCH, P. TALLERICO, LANL

The Accelerator Production of Tritium project (APT) utilizes a 1700 MeV, 100
mA proton Linac. The radio frequency (RF) power is provided by 244
continuous wave (CW) klystron amplifiers at 350 MHz and 700 MHz. All but
three of the klystrons operate at a frequency of 700 MHz. The 350 MHz
klystrons have a nominal output power of 1.2 MW at a DC-to-RF conversion
efficiency of 65%. They are modulating-anode klystrons and operate at a beam
voltage and current of 95 kV and 20 A. The design is based on the CERN
klystron. The 700 MHz klystron is a new development for APT. Three 700 MHz
klystrons are currently under development. Two vendors are each developing
our baseline klystron that has a nominal output power of 1.0 MW at a
DC-to-RF conversion efficiency of 65%. A 700 MHz klystron is also under
development that promises to provide an efficiency in excess of 70%. The 700
MHz klystrons operate at a maximum beam voltage of 95 kV and a maximum beam
current of 17 A. The test results of these klystrons will be presented and
the design features will be discussed.

*Work supported by the U.S. Department of Energy.

Classification Category: T04

The numbers are from http://www.permanent.com/p-sps-tc.htm

which in turn based their numbers on the US DOE Solar Power Satellite
Concept Development and Evaluation Program (SPS CDEP), Final Report

If we can get ahold of the initial report, we can find out what the DOE
report based their numbers on.

Tom M.
TomM@...

>I am concerned that the numbers from this study have no basis. The
>real-world numbers that I have been able to find on DC to RF to Antenna
>are less than 50%. Perhaps the first goal would be to find actual
>data to support or modify these numbers so that there is a clearer
>starting point.

>Mitchell James
>mejames@...
>http://www.InnerTransit.net (Email distribution for multilevel
organizations)

> I am concerned that the numbers from this study have no basis. The
> real-world numbers that I have been able to find on DC to RF to Antenna
> are less than 50%. Perhaps the first goal would be to find actual
> data to support or modify these numbers so that there is a clearer
> starting point.
>

Mitchell, the 50% number was a SWAG from a company who builds radar systems. Requirements for SPS are different than radar, and different technologies can be used. The design can be optimized differently.

It takes a lot more than a couple of phone calls to get real data. It will take a serious study contract of about $100K to get useful results IMHO.

Also, be wary of ITAR before publishing technical results.

It is a very valid question, what specific technologies can be used, and at what frequencies to get
the maximum efficiency? 2.4 GHz was chosen because of good atmospheric propagation, but it is probably not the best frequency from a DC-RF or RF-DC dissipation standpoint.

> If we would like SPS's to be implemented in the near term, they must have a
> comparable price per KW for terrestrial based energy sources.
>

1) I disagree.

2) If that claim is true then we should give up now. It will NEVER be possible for SPS to be cheaper than fossil fuels. Fossil fuels can keep us going for a couple of centuries.

As I have stated several times, SPS is only a viable competitor to fossil fuels at such time as people believe that global warming is a problem, and serious alternatives to fossil fuels must be found.

The biggest force that could drive SPS is the Kyoto Treaty. If the USA changes their stance and throws their weight behind Kyoto then SPS will come a lot closer.

Right now, the best market for SPS would appear to be countries which have or will ratify the Kyoto Treaty. Who might they be ?

Charles R.

> Right now, the best market for SPS would appear to be countries which
> have or will ratify the Kyoto Treaty. Who might they be ?
>
> Charles R.
>

There was a report on National Public Radio a few days ago on how Germany
is working to position itself as a leading supplier of green technologies
as the world begins to implement the Kyoto Protocol. As such, that
government might be a good source of collaboration.

--Justin

Charles Radley wrote,

"Fossil fuels can keep us going for a couple of centuries."

I agree. Even if we eventually run out of oil and/or coal, we could then
move on to using methane hydrates (c.f.
http://marine.usgs.gov/fact-sheets/gas-hydrates/title.html ). There's a
lot of hydrocarbons on this planet.

Ron Menich

>So, I suggest that the next order of action would be to contact
Mr. Rees and
>see if he can provide additional information,
>

Tom are you going to contact him or should I?

Mitchell James
mejames@...
http://www.InnerTransit.net (Email distribution for multilevel organizations)
http://www.InnerTransit.org (Homebase for collaborative engineering)

>Mitchell, the 50% number was a SWAG from a company who builds radar
systems. Requirements for SPS are different than radar, and different
technologies can be used. The design can be optimized differently.

>

True, but it is a SWAG but it is from people who are currently in
the business of building phased array antennas. It is quite possible
that phased array is not the way to go.

>It takes a lot more than a couple of phone calls to get real data.
It will take a serious study contract of about $100K to get useful
results IMHO.

Well, nobody on this list seems to be offering up money to pay somebody
to find out. So we will just have to find people to find that answers
from.

Mitchell James
mejames@...
http://www.InnerTransit.net (Email distribution for multilevel organizations)
http://www.InnerTransit.org (Homebase for collaborative engineering)

Mitchell,

go ahead and contact him if you would please,

Tom M.
TomM@...

>So, I suggest that the next order of action would be to contact
Mr. Rees and
>see if he can provide additional information,
>

Tom are you going to contact him or should I?

Mitchell James
mejames@...
http://www.InnerTransit.net (Email distribution for multilevel
organizations)
http://www.InnerTransit.org (Homebase for collaborative engineering)

>
> >Mitchell, the 50% number was a SWAG from a company who builds radar
> systems. Requirements for SPS are different than radar, and different
> technologies can be used. The design can be optimized differently.
>
> True, but it is a SWAG but it is from people who are currently in
> the business of building phased array antennas. It is quite possible
> that phased array is not the way to go.
>

The efficiency is not a function of the antenna design, it is a function of the technology of the transmitting
device(s) which feed the antenna. Antennas themselves all have an efficiency of close to one, whether they are a phased array, or a dish or yagi or whatever.

Actually, I would expect a phased array to have a smaller loss than, say, a dish, but the difference should not be significant.

Firstly my apologies for the length of this post, the disjointedness and
the simplicity of parts of it.

One important thing to remember in the Ground vs SPS debate is that
there is no continuing fuel costs involved in supplying the electricity.
Over the expected lifetime of either Power supply this adds up to a
great difference in the costs of each. The main cost in an SPS is in the
initial period of construction. The Cost in a conventional power station
are ( I assume ) spread out throughout its life.

I would also guess that the maintenance costs of each would be similar
for a comparable sized Power Station. SPS designs have virtually no
moving parts compared to Ground based Stations which considerably
decreases the amount of maintenance required. This is offset by the
higher cost in supplying that maintenance. ( does anyone know of
approximate costs for maintenance for conventional Ground and SPS ? )

Can someone answer these questions for me please as I don't have access
to the data for it. What is the largest sized of conventional ground
based Power Station in Output , is it in the MW or GW ? and the average
sized station. Also what is the initial capital cost of both of these
for say , coal, gas and possibly Hydro ( I am intentionally ignoring
Nuclear due to the waste disposal issue, I am also ignoring Wind and
Ground based Solar as they are not capable of supplying Base load
electricity ) and the ongoing fuel costs for gas and coal.

From what I have seen on the Web an SPS would be built to supply at
Output from Rectenna to the Grid anywhere from 1 GW up to 25 GW with 10
GW seeming to be a standard number. In Geostationary orbit from what I
have seen, it is able to supply this for 98% of the year with only a gap
of approx 1 hour per day for 22 days around the equinoxes due to eclipse
by the earth ( again if someone has more detailed information on this
can they please post - also does anyone know what local time this would
approximately coincide with at the rectenna station ? I would assume
around midnight but am not sure )

If the power supply from the SPS is aimed at the supplying Base Load,
then it would be utilized at approximately 85 - 95% of the time. The
Peak demand of power can then be supplied by smaller conventional power
stations which are fired up on demand, and coincidentally be used to
supply the power for the other 2 % of the year.

Here in Australia we pay at home between 8 c / kwh ( all currency is in
Australian $ ) and 25 c / kwh depending on where we live and the usage
of the electricity. This cost covers the generation of the power, and
the construction and maintenance of the Power lines. For the SPS I would
suggest aiming the market not at the consumer but at the current
electricity suppliers. by this I mean sell the electricity from the
Rectenna station direct to the Companies that look after the Power lines
and current Power Stations. I suggest this for two reasons, One is
demand is continually outstripping supply, and secondly there are older
stations that are going to need replacement on a regular basis.

If we can aim to supply this Electricity at an initial cost of around 10
- 11c / kwh and then later once more SPS are set up and the cost
involved drop, we can lower this to around 5 c / kwh. For the last
couple of years Australian Electricity consumers have been given the
opportunity to pay a few cents more for their electricity and have it
sourced from "Green" Power Supplies. The demand for this scheme is so
great that the Electricity companies have a much greater demand for
Green Power than they can supply, which is leading to a number of
projects in this area. ( for those interested in this scheme you can
choose the % of your electricity to come from Green Power, thus allowing
for everyone to help with the environmental cause, even if it is only on
a small basis. This came about from a Government initiative a couple of
years ago, mainly to do with Kyoto from memory )

Now at 10 c / kwh and taking a single SPS supply 10 GW we have ( If
someone spots a mistake here feel free to correct and the figures are
rounded a little )

10 GW x 24 Hours x 365 days x 98 % of sunlight x 85% worst case usage =
total power supplied which gives
7.297 x 10 ^ 13 Wh assuming I haven't stuffed up somewhere which gives
7.297 x 10 ^ 10 Kwh multiply this by 10 c or $0.10 gives
$ 7,297,080,000 ( Australian Dollars ) income Per Year
now take the average lifespan of a Power Station to be 25 years and you get
$ 182,427,000,000

Which is sure to be a little more than what it cost to build in the
first place even allowing for it to be the first one and the usual cost
overruns that go with that. And the cost of maintenance would not change
the figures much. To cover the possibility that we can't sell all the
electricity we should take a percentage of that , but I'll let someone
else work that out. Even if it turns out that the first one cost more
than this, try changing the rate to 15c/ kwh and see what a difference
that makes. as long as the public perception is there , and it is most
likely to be for the next few years, then people would be happy to pay
this in the short term, remembering that the electricity company we
supply the Power to would have their own costs and profit to maintain,
and that the costs will go down.

Now add to that the fact that in 1995/96 Australia consumed 1,248,711 GW
of electricity, which is 142.54 GW generating capacity on average. (
Unfortunately I have lost track of the book where these figures come
from,they were part of a course I did at one stage a couple of years ago
) and you get the idea of the size of the available market, and this has
increased since then. I don't have reliable figures for the US, Europe,
India and China whose markets are growing very rapidly , but you get the
idea. Even if you managed to capture only 20 % of the market in
Australia, you are talking about a lot of money. Capture 20 % of the
World market, and you are talking about a phenomenal amount of money.
And of course you would not stop at one SPS but continue building them,
as your experience and infrastructure for manufacture increase, the cost
per SPS will drop and you can supply the electricity for cheaper and
gain a larger market share ( In Theory ) As it is the First one will
be the Hardest and most expensive to build, particularly as most of it
would probably be done here on Earth. Once it is proven and Money starts
coming in , then you can build more and more components using the Moon
and Neos, and work your way up to an Island One as a manufacturing base.
I would envision that once the first few are out the way , you would be
aiming at a supply rate of 1 new SPS at least every 6 months. At that
rate , it will still take a Number of years to Saturate the Market, and
then you can move the production to other things while still providing
the occasional SPS for earth.

Now for the Downside. As Tom said we need accurate figures for
maintenance, building and assembly. And for various scenarios, eg
initially earth built, and then built with moon, and Neos etc and
maintenance by human and / or Telerobotics.
For comparison, we should also find those figures for conventional power
stations, with Fuel cost added in.

You may wonder why I am focussed on the money side of things, well with
these sorts of income and profits you can do a lot of other things, like
island 1's , Space Tourism, Moon bases, even a Mars Trip on the side
etc. All you need is somewhere to Start. Once One company has built an
SPS there no doubt will be more springing up, even so it is a Very Large
Market, and it will help open up more markets in other areas.

Now I'll hand it over to someone else who can rip all my assumptions to
bits no doubt ;) still it is nice to dream.

NB: The cost for electricity that I used are ones that I have paid at
various places I have lived. The other figures come from various places
which I have lost track of since the course I did in which I first came
across them , my apologies I know that isn't good science, but for a
rough estimate they will do, I was just lucky that I had some of my
notes with the figures in them.

>
> I am concerned that the numbers from this study have no basis. The
> real-world numbers that I have been able to find on DC to RF to Antenna
> are less than 50%. Perhaps the first goal would be to find actual
> data to support or modify these numbers so that there is a clearer
> starting point.
>

The 1979 DOE/NASA study assumed Klystorn tubes, which have efficiency of
85%.

The guys you spoke to quoted the following technology (not sure why):-

>
>You can assume a GaN device through HRL.
>

I do not know what those acronyms mean, perhaps somebody could clarify.

Presumably this technology has a 40% limitation.

You might ask them if they would get better efficiency using Klystrons.

And surely there is some solid state technology by now which is better
even than Klystron.

CR.

Dear B,

The following old posting from Usenet addresses more of the quesitons
and points you raise
so I am cross-posting it here.

power
satellite)
Date: Sat, 08 Nov 1997 22:14:06 GMT

>: With SPS', on the other hand, the technology is well in hand. We have the solar
>: cells and the beaming technology, and they have been well tested over more
>: than a decade. The primary question of one of economics.
>
>: Abou 5 years ago, at a Space Frontier Federation conference, a paper was
>: presented by a power company showing an analysis of the profitibility of small
>: SPS systems, 10 MW or so. The analysis showed that they could be economically
>: viable, with power costs on the order of that produced by nuclear reactors -
>: and that without major advances in launch technology.
>
>Not every one is convinced they are economically viable. At the NSS Space
>Summit, Robert Zubrin said that he thought the ideas of Gerard O'Neill
>were absurd, since space solar power presently cost a thousand times more
>than any other type.
>
>Karen

Karen, my guess is solar power satellites could compete with
alternate sources of energy on cost, if the US followed the proper
development path.

Found at: http://pages.nyu.edu/~potter/thin-film-sps.html

"The SPS [Solar Power Satellite] designs mentioned above [NASA/DOE
baseline studies] have masses of about 50,000 metric
tons and generate 5 GW (gigawatts, or thousands of megawatts) of
electricity. Recently, therefore, another strategy for reducing SPS
launch costs has been considered. Work at the NASA Lewis Research
Center has shown that it may be possible to use thin-film solar cells
deposited on a lightweight substrate along with solid state microwave
transmitters. Since the entire area of the substrate can be covered
with microwave transmitters as well as solar cells, large effective
transmitting antenna diameters become feasible. Due to the physics of
power beaming, the larger the transmitting antenna, the less the
microwave power beam will spread as it reaches the Earth. Since the
rectifying antenna (rectenna) at the Earth's surface can now be made
correspondingly smaller, the SPS need not supply as much power as a
conventional SPS in order to be economical. (Indeed, it ought not to
supply as much power, or else the microwave beam will become too
intense.) With smaller SPS's having a lower mass per kilowatt of power
generated, the system becomes easier to build and finance.

Current research at New York University, supported by SSI [Space
Studies Institute], aims to achieve the best of both approaches to
launch cost reduction by using thin films and lightweight substrates
built from lunar materials. The first step in the study was to
consider two lightweight SPS designs suggested by Geoffrey Landis and
Ronald Cull of the NASA Lewis Research Center: the "bicycle wheel"and
the "inflatable sphere."

"A bicycle wheel SPS using thin-film technology will have a diameter
of just over 4 kilometers for a power beam frequency of 2.45 gigaherz
(this is the frequency of the NASA/DoE reference design). It will
supply about 450 megawatts of power to consumers. The mass of the
solar cell/transmitter array (including the substrate, but not the
support structure) is just over 200 metric tons if Kapton is used for
the substrate (terrestrial materials), and just under 800 tons if
steel foil is used (lunar materials). The effect of increasing the
frequency was also considered. A 10 GHz power beam yields a bicycle
wheel SPS that has half the diameter, and thus one-fourth of the array
mass and power level as the 2.45 GHz design; i.e., roughly 2 km, 50
tons (terrestrial) or 190 tons (lunar), and 110 MW. A bicycle wheel
with a mirror, or an inflatable sphere will be 8.5% smaller in
diameter and supply 19% more power than a conventional bicycle wheel,
due to th e elimination of the tracking loss. Higher frequencies will
yield even smaller, more easily constructed SPS's, but the amount of
power for their size will be lower, since higher frequencies are
subject to rain and air attenuation, and solid state microwave
transmitters are less efficient at higher frequencies.

Using thin-film technology, an SPS in low Earth orbit may be light
enough to be launched by a single Space Shuttle mission. For a bicycle
wheel SPS orbiting at an altitude of 1200 kilometers, beaming power at
a frequency of 10 GHz, the diameter would be 340 meters, the power
available to consumers would be 3 MW, and the array mass would be an
amazingly low 1430 kilograms (though the support structure would
increase the mass). The full capacity of such an SPS can be exploited
if a series of SPS's and equatorial rectennas are spaced such as to
enable a given rectenna to lock onto the next SPS after the previous
one has disappeared from view. The previous SPS would then lock onto
another rectenna, further east."

Two other good links:

http://pages.nyu.edu/~potter/sps.html

http://web.mit.edu/techreview/www/articles/oct97/hoffert.html

Now, let's compare the cost of construction of three nuclear
powerplants with using thin-film solar power satellites. As an
example, I believe the Tennessee Valley Authority at one time planned
on costructing (now cancelled) three nuclear powerplants at a cost of
$9 billion and each powerplant was rated at about 800 Megawatts output
or 2,400 MW total.

If we wanted to supply 2,400 megawatts using thin-film solar power
satellites, what would it cost? Let's use the 10 GHz bicycle wheel
SPS with a mass of 50 tons and an output of 110 MW, which means we
need to put 22 thin-film SPS in geosynchronous orbit (GEO) to equal
the output of the three nuclear powerplants.

We don't have a launch vehicle capable of putting 50 tons in GEO in
one launch so we need to develop one. Estimates for a shuttle-derived
heavy-lift vehicle (Shuttle-C) of this capacity are around $3 billion
in development costs, and George H estimates his Big Dumb Booster
(BDB) at about the same development cost.

George thinks he can launch his BDB for about $50 million per launch
and I think a Shuttle-C can be launched for about the same, so I'll
use $50 million as the launch cost for each SPS.

Heavy-lift vehicle development= $3 billion

Cost to launch 22 SPS= $1.1 billion

Now, if the SPS materials costs, ground facilities and receiving
antenna costs are around $5 billion, then thin-film SPS look superior
to nuclear powerplants, especially when you consider that the costs of
nuclear cleanup have not been calculated into the cost comparison,
and, for the future, the next 22 SPS put in orbit will not incur the
$3 billion development cost for the heavy-lift launch vehicle since
it's already developed.

There's no doubt we can build a heavy-lift vehicle to perform this
task. All it takes is a small addition to space policy authorizing a
heavy-lift vehicle. In fact, NASA seems to be working fairly steadily
towards that goal right now, in conjuction with manned Mars missions.

The only questions I see are the state of the thin-film technology and
that would seem to be easily surmountable if it became US government
policy to get serious about SPS. Maybe Geoffrey Landis can bring us
up to date on the status of developments in this area (the reports I
excerpted above were done in 1994).

China is currently building a dam across the Yangtze River that will
inundate and desecrate some of the most beautful and historic places
on Earth and will drown thousands of archeological sites, not to
mention dislocating 1.2 million Chinese people and thousands of acres
of farmland. This dam will produce18,000 megawatts of electricity and
will cost about $25 billion.

We could launch 166 thin-film SPS into orbit for $8.25 billion in
launch costs (sounds like a good project for USA:) and these 166 SPS
would supply as much power as the Yangtze dam; without the ecolgical
and social consequences.

I think Solar Power Satellites deserve another, serious look, Now.
Especially now. We're talking TRILLIONS of dollars in future power
production revenues, and we're talking about the very survival of many
species on Earth and the quality of life of the rest. The solution
seems to be right before our eyes, and within our grasp.

Tom Abbott

Charles,

Thanks for the forwarded posting, very interesting.

As opposed to a BDB, has anyone looked into the development costs of the
laser based launch technology(s), specifically the light craft?

See http://www.islandone.org/Propulsion/JordinKareBiblio.html

and

http://www-phys.llnl.gov/clementine/ATP/Laser.html

and

http://www-aero.meche.rpi.edu/Curriculum/TAVD/

The creator of the light craft is

Associate Professor Leik N. Myrabo
myrabl@...

He might be able to provide cost and time related guesstimates. It
apparently takes a 1 megawatt laser to launch 1 kg into orbit, and expected
cost would be roughly 200$ a kilogram.

Another possibility is to use a rail gun. I realize that heating can be a
problem, but if we use a laser nose cone, the laser heating can create a
teardrop around the craft resulting in no friction against the craft and
hence no heating.

Since we are accelerating hardware, the rate of acceleration shouldn't be as
much of a problem.

Tom M.
TomM@...

>
> Charles, I am apologizing in advance if you are offended but the
> following is not directed at you.
>

Thank you for softening the blow :-)

I am glad my posting has provoked some more objective discussions.

> The paragraph above just tends to make my blood boil. It is full of
> the self serving NASA style propaganda. Papa NASA knows best so don't
> worry your little blond head. In case you really try to understand

NASA Glenn Research Center (frmerly NASA Lewis) has a lot of very
talented people working in this area, such as Dr. Geoffrey Landis. They
have a great space power web site with some excellent resources.

Having side that, there are definite problems with the thin film design
described, some of which you hit on.

The biggie is that the PV cells & the antenna need to be independently
steerable, because the direction of the sun verusus the direction of the
rectenna will not be fixed, and well continuously change.

>
> "Large effective transmitting antenna diameters" is more near field
> nonsense. Nobody knows how to make a very large near field antenna.

The theory is well understood.
How to actually build one that works is very difficult.

> Phased array antenna (a requirement for having a near field antenna)
> require precision alignment and a rock steady support structure. Just

These are key requirements which must be worked on.

> putting a bunch of emitters on a thin film does not make a phased
> array! The concept of the dynamics involved with spinning the thin
> film, the push from the microwaves leaving, the push from sunlight,
> the off axis mirror forces, the heat dissipation stuff. None of it
> decoupled so that any minor problem in one force could send the whole
> thing spinning out of control. A billion dollars of crumpled foil.

It is not that bad.
The disturbance forces you mention are all controllable.
It will require a sophisticated active control system.
Certainly this area needs more research.
Sophisticated computer models will be needed to optimize the control
laws.
But yes, it is not a simple passive design, which might have been
implied.

My preferred approach for large structures is inflatable concentric
toruses of different diamterers,
aligned with long inflatable tubes.
Spinning centrifugally would add some stiffness. but would complicate
the control system.
We need some realistic simulations and flight testing to decide between
the options.

>
> > Date: Sat, 08 Nov 1997 22:14:06 GMT
> > ...
> > launch costs has been considered. Work at the NASA Lewis Research
> > Center has shown that it may be possible to use thin-film solar
> > cells
> > deposited on a lightweight substrate along with solid state
> > microwave
> > transmitters. Since the entire area of the substrate can be covered
> > with microwave transmitters as well as solar cells,
> The paragraph above just tends to make my blood boil. It is full of
> the self serving NASA style propaganda. Papa NASA knows best so don't
> worry your little blond head.

To be fair Mitchell, of all the work being done at NASA, IMHO the Space
Power work at Glenn Research Center (formerly NASA Lewis) is the most
valuable thing the agency is doing today. I would shut down large
portions of NASA if I could, including a couple of entire centers.

But the NASA GRC Space Power Office is the one project office which I
would give as much funding as I possibly could. They are amongst the
world leaders in the field and truly advancing the state of the art.

====

Thinking more, I actually rather like the idea of a sun pointed spinning
disk as the primary priamry platform.
The phased array could be on a sun pointing disk because the beam can be
steered without reorienting the disk, I had forgotten about that -
mental lapse. The phased array needs to only occuppy the central
kilometer diameter disk, the remaining 9 km diameter of solar cells need
not be so flat.

The centrifugal spin can exert a high tension and thus result in a
structure with a good degree of flatness. Elements of the array which
are too far outside the allowable surface can be shut down so they do
not disrupt the field. A lot of post deployment adjustment and
tweaking could be done by astronauts and robots to get everything into
alignment.

Real time structural dampers will be needed to deal with disturbance
forces.

Thermal dissipation is certainly a major problem and could drive us to
use a frequency which is sub-optimal from an atmospheric transmission
standpoint.

The paragraph above just tends to make my blood boil.
My main problem with the integrated-solar-cell-and-solid-state-microwave-emitters proposal is that you can either point your solar array at the sun, or your transmitter at the Earth, but not both at the same time. I've seen designs that added mirrors to increase insolation on the PV, but they strike me as a Rube Goldberg solution to the problem.
I was never aware that the requirement for a power bus on a SPS was a difficult problem in need of a solution. According to those efficiency numbers just posted, bus efficiencies were in the high 90's. I say build a PV array, build an antenna, connect them with a rotary joint, and point the PV squarely at the sun and the antenna squarely at its rectenna.
Also, I've been bothered by all the proposals for LEO SPS. They are far more complex than GEO satellites. Continuous sunlight, to me, is the most major advantage over ground-based solar, so to me if you give that up, you might as well throw in the towel. The fact that anybody's even considering LEO SPS just shows how our ambitions have telescoped inwards.
I know, they're just trying to find a terraced approach to the SPS we all want to have. And I'd agree a terraced approach would be great. But an early SPS whichsurrenders the single most significant advantages over ground-based solar of the original concept, with lots of added disadvantages, may do the concept more harm than good.

Regards,

Mike Combs

>My main problem with the integrated-solar-cell-and-solid-state-microwave-emitters proposal is that you can either point your solar array at the sun, or your transmitter at the Earth, but not both at the same time.
>

Actually you can. The phased array antenna can point the beam towards any direciton in a hemisphere, even if the surface of the antenna is not normal to the target.

>I've seen designs that added mirrors to increase insolation on the PV, but they strike me as a Rube Goldberg solution to the problem.
>

The SPS mounted mirrors I have seen are for a different reason.
They are not even steerable.
Typically they are for GaAs array (not for Si) which can run at a higher temperature. Because mirrors are cheaper than
PV cells, they are used to insrease the collecting area.

You cannot do this with Si cells because they cannot withstand the higher temperatures.

writes:

>My main problem with the integrated-solar-cell-and-solid-state-microwave-emitters proposal is that you can either point your solar array at the sun, or your transmitter at the Earth, but not both at the same time.
>

Actually you can. The phased array antenna can point the beam towards any direciton in a hemisphere, even if the surface of the antenna is not normal to the target. True, and correct me if I'm wrong, but aren't there limits to the beam deflection one can achieve within the limits of practicability? I'm thinking of situations like where the Earth is at a 90 degree angle to the sun. >I've seen designs that added mirrors to increase insolation on the PV, but they strike me as a Rube Goldberg solution to the problem.

The SPS mounted mirrors I have seen are for a different reason.
They are not even steerable.
Typically they are for GaAs array (not for Si) which can run at a higher temperature. Because mirrors are cheaper than
PV cells, they are used to insrease the collecting area. No, I wasn't thinking about those kinds of mirrors when I made the comment. Those kinds of mirrors are very sensible for the reasons you give. I was referring specifically to the integrated PV/solid-state-antenna designs where the structure must point (more or less) toward the Earth, and the sun's at a 90 degree angle, so we use a mirror to reflect sunlight onto the PV surface of the structure. The mirrors have to go through some strange rotation relative to the rotation of the platform, and the whole thing struck me as hellishly complicated. The kind of fixed mirrors you mention are way cool, and will come even more into play as we move further from the sun.

Regards,

Mike Combs

Date: Wed, 1 Aug 2001 08:07:26 -0500
True, and correct me if I'm wrong, but aren't there limits to the
beam deflection one can achieve within the limits of practicability?
I'm thinking of situations like where the Earth is at a 90 degree
angle to the sun.
==============

Indeed.
There will be outages during those times,
I think this will occur for up to an hour per day in GEO.

==============
I was referring specifically to the integrated
PV/solid-state-antenna designs where the structure must point (more
or less) toward the Earth, and the sun's at a 90 degree angle, so we
use a mirror to reflect sunlight onto the PV surface of the
structure. The mirrors have to go through some strange rotation
relative to the rotation of the platform, and the whole thing struck
me as hellishly complicated.
=============

Yuck !