Solar-pumped laser power transmission, a way to dramatically decrease launch costs?

On Dec 29 2009, 11:44*pm, Sylvia Else
wrote:
BradGuth wrote:
On Dec 19, 9:16 pm, Sylvia Else wrote:
BradGuth wrote:
On Dec 17, 8:37 pm, Sylvia Else wrote:
Jonathan wrote:
I like this idea, *Relatively small mirrors would power
the lasers, not huge solar cell arrays. The lasers would
transmit their beams to other satellites that convert it to, and
beam it down, as microwaves. * No need for mile-size
collectors in orbit.
Proceedings of the ASCE Earth&Space 2006 Conference
April 2006
Space Power Grid- Evolutionary Approach To Space Solar Power
"At a higher level, a direct solar-pumped laser could be used to
convert solar energy on the LEO satellites, and transmit the laser
beams to other satellites where the demand for power is greater
(e.g., satellites over the dark side of earth). Recently, development
of such *lasers has reached a stage where efficiency of up to 38%
has been shown. These satellites would receive incoming
laser energy using their high-efficiency narrow-band photovoltaic
cells, convert it to microwave, and beam it to Earth. This
architecture has two advantages: the beaming to Earth
could be done at optimal microwave frequencies for maximum
transmission through the atmosphere, without requiring excessive
transmitter size. The laser beams would propagate with very
high efficiency, and require only small collectors. Thus the mass
and overall cost per unit power of the system with this architecture
may be substantially lower than the lower-risk option
presented before."
http://www.adl.gatech.edu/archives/adlp06040601.pdf
And it should be noted, the SPS start up company, Space Energy Inc,
maybe one of the more legitimate commercial attempts at SPS, has
as one of it's technical advisors this guy, and his /current/ specialty
might be a clue of things to come.....
Dr. Richard Dickinson
Space Energy Inc technical advisors
"Mr. Dickinson is one of the world's foremost experts on Wireless
Power Transmission (WPT). President of OFF EARTH-WPT,
Mr. Dickinson was Group Supervisor of the High-Power Transmitter
Group at Goldstone and was NASA's microwave power transmission
specialist on the Solar Power Satellite Reference System team....
.....he is currently involved in studying and designing the solar pumped
laser-power beaming phased array for interstellar missions."
http://www.spaceenergy.com/s/TechnicalAdvisors.htm
What's missing, as always, is any detailed costing. It's easy to wave
one's hands around, and conjure up systems that could be made to work
technically. But the bottom line is the bottome line, and as usual, it's
concealed.
Sylvia.
Whatever anyone else can do, our WilliamMookcan do it better and
cheaper, as long as it never involves his own loot. *Space Energy
seems capable enough and willing to risk at least some of their own
loot.
Well, I wouldn't be so sure about that. Their web site says nothing
about finances that I can see, but the resumes of the directors are
interesting

http://www.spaceenergy.com/s/Directors.htm

It seems likely they'll know more about money, and how to get it, than
about the technology.

Sylvia.

Perhaps once they get our rich and powerful WilliamMookon their
side, they'll be all set. *Eventually (a couple spendy decades from
now) they'll deliver that wholesale $1/kwhr of clean energy that most
of us can't afford.

There are two kinds of people. Some regard money as a way of getting
technology, and the others regard technology as a way of getting money.

Sylvia.

Sylvia,

Put them together. Its a self-propagating loop! Technology makes
money. Money makes technology. They go together and the goal is to
have a multiplier (x) greater than one per iteration

V(n+1) = x * V(n)

William Mook writes:
Put them together. Its a self-propagating loop! Technology makes
money. Money makes technology. They go together and the goal is to
have a multiplier (x) greater than one per iteration

V(n+1) = x * V(n)

As opposed to:

V(n+1) = (aV(n) + c) mod m

whe

m 0
0 a m
0 = c m
0 = Vo m (and if c=0, Vo 0)

whereby it helps if...

1. c and m are relatively prime
2. a-1 is divisible by all prime factors of m
3. a-1 is a multiple of 4 if m is a multiple of 4.

;-)

Dave

http://en.wikipedia.org/wiki/Linear_...tial_generator

OM writes:

...I dunno, David. Lemme pull my old D&D Dungeon's Master Screen out
of storage and see if the numbers add up. I think you may have made a
mistake, basing everything on a D4 roll instead of a D6.

OM


;-)

Dave

David Spain writes:

As opposed to:

V(n+1) = (aV(n) + c) mod m

whe

m 0
0 a m
0 = c m
0 = Vo m (and if c=0, Vo 0) --

FYI, this is wrong, if c=0, Vo must be co-prime to m.

Sorry.

;-)

Dave

On Jan 5, 9:09*pm, David Spain wrote:
David Spain writes:
As opposed to:

V(n+1) = (aV(n) + c) mod m

whe

m 0
0 a m
0 = c m
0 = Vo m *(and if c=0, Vo 0) --

FYI, this is wrong, if c=0, Vo must be co-prime to m.

Sorry.

;-)

Dave

The growth factor leading to exponential growth in my original Jan 2
post was based on organic or natural feedback that is known to occur
in nature/society/industry.

What is the natural or organic process that leads inevitably to the
modulo function you claim here? Unintended consequences? Resource
depletion? How does that work? I presume you don't need to know how
exponential growth works in an infinite field of resources right?

I mean, we have reached limits to growth - assuming we stay on
Earth.

Assuming we move off-world, we have not reached limits to growth.

Given the fact that very high living standards lead to ZPG
reproductive rates - exponential growth will stop - if we take the
next step. Also, if that happens after interstellar transport
develops, human density will drop to nearly zero 200 light years from
Earth.

If this is a general rule, and if technical civilizations are more
than 200 light years apart - this answers the Fermi Paradox.

Check it out.

Population is stable in a subsistence culture. As the people
industrialize, their population growth rates rise -peaking about 2%
per year - at about $10,000 per person per year (in 2008 dollars) -
then, as per capita income rises above $10,000 per person per year
population growth rate declines - until it reaches ZPG at $30,000 per
person per year - AND NEGATIVE THEREAFTER.

Since economic growth rates under ideal conditions can be maintained
at 6% or more per year, we can see that unlimited development off
world leads naturally to a situation where population peaks. The peak
will be determined by how fast economic growth is maintained. Any
economic hiccup or reversal leads to massive spikes in population -
until there is a collapse due to depletion or pollution or disease or
war.

Which is another modulo function I suppose.

But I'm more interested in positive visions of the future.

If we could sustain 6% growth rate in our economy today, using off-
world assets, we would see our population peak at 9.12 billions by
2032. (see table below)

The interesting thing

Year Income Population $/Year
2008 $70,000 6.80 $10,294.12
2009 $74,200 6.93 $10,700.89
2010 $78,652 7.07 $11,128.18
2011 $83,371.12 7.20 $11,577.39
2012 $88,373.39 7.33 $12,050.04
2013 $93,675.79 7.47 $12,547.81
2014 $99,296.34 7.60 $13,072.53
2015 $105,254.12 7.72 $13,626.23
2016 $111,569.37 7.85 $14,211.11
2017 $118,263.53 7.97 $14,829.63
2018 $125,359.34 8.10 $15,484.51
2019 $132,880.90 8.21 $16,178.73
2020 $140,853.75 8.33 $16,915.66
2021 $149,304.98 8.44 $17,699.02
2022 $158,263.28 8.54 $18,532.99
2023 $167,759.07 8.64 $19,422.25
2024 $177,824.62 8.73 $20,372.10
2025 $188,494.10 8.81 $21,388.50
2026 $199,803.74 8.89 $22,478.24
2027 $211,791.97 8.96 $23,649.05
2028 $224,499.48 9.01 $24,909.79
2029 $237,969.45 9.06 $26,270.65
2030 $252,247.62 9.09 $27,743.43
2031 $267,382.48 9.11 $29,341.82
2032 $283,425.42 9.12 $31,081.88

After this point, population begins to fall off;

2033 $300,430.95 9.11 $32,982.47
2034 $318,456.81 9.08 $35,066.00
2035 $337,564.22 9.04 $37,359.22
2036 $357,818.07 8.97 $39,894.37
2037 $379,287.15 8.88 $42,710.63
2038 $402,044.38 8.77 $45,856.12
2039 $426,167.05 8.63 $49,390.64

It is unlikely that population will decline faster than 2% per year -
given the fact that people live for more than 50 years. In fact
longevity increases will limit the decline to less than 1% once
universally applied

2040 $451,737.07 8.46 $53,389.33
2041 $478,841.29 8.29 $57,747.64
2042 $507,571.77 8.13 $62,461.73
2043 $538,026.08 7.96 $67,560.65
2044 $570,307.64 7.80 $73,075.80
2045 $604,526.10 7.65 $79,041.17
2046 $640,797.66 7.50 $85,493.52
2047 $679,245.52 7.35 $92,472.58
2048 $720,000.26 7.20 $100,021.36
2049 $763,200.27 7.05 $108,186.37
2050 $808,992.29 6.91 $117,017.91

By 2050 there will be as many people alive then as there are today,
and the world will be generating nearly a quadrillion dollars per
year, and the average family of four will be earning nearly $1 million
per year!

We can have commodity starships and space colonies driven by sun
orbiting solar pumped laser light sail by 2025 - 2050 time frame. Bob
Forward, chief scientist at Hughes Aerospace showed in 1983 that such
vehicles were capable of 1/3 light speed.

So, adjusting our figures for this at 2050

0.2% reduction of underlying population - due to life span exceeding
500 years and
4% per year leaving the Earth to points beyond
and increasing income growth to 8% per year to reflect increasing
automation and robotics

we have the following charts after 2050

Total population continues to decline slowly and income skyrockets

2050 $808,992.29 6.91 $117,017.91
2051 $873,711.67 6.90 $126,632.61
2052 $943,608.60 6.89 $137,037.29
2053 $1,019,097.29 6.87 $148,296.87
2054 $1,100,625.08 6.86 $160,481.58
2055 $1,188,675.08 6.84 $173,667.44
2056 $1,283,769.09 6.83 $187,936.71
2057 $1,386,470.62 6.82 $203,378.40
2058 $1,497,388.26 6.80 $220,088.85
2059 $1,617,179.33 6.79 $238,172.31
2060 $1,746,553.67 6.78 $257,741.57
2061 $1,886,277.97 6.76 $278,918.74
2062 $2,037,180.20 6.75 $301,835.91
2063 $2,200,154.62 6.74 $326,636.05
2064 $2,376,166.99 6.72 $353,473.89
2065 $2,566,260.35 6.71 $382,516.83
2066 $2,771,561.17 6.70 $413,946.07
2067 $2,993,286.07 6.68 $447,957.67
2068 $3,232,748.95 6.67 $484,763.81
2069 $3,491,368.87 6.66 $524,594.10
2070 $3,770,678.38 6.64 $567,697.03
2071 $4,072,332.65 6.63 $614,341.47
2072 $4,398,119.26 6.62 $664,818.43
2073 $4,749,968.80 6.60 $719,442.79
2074 $5,129,966.31 6.59 $778,555.32
2075 $5,540,363.61 6.58 $842,524.79
2076 $5,983,592.70 6.56 $911,750.28
2077 $6,462,280.12 6.55 $986,663.63
2078 $6,979,262.53 6.54 $1,067,732.18
2079 $7,537,603.53 6.52 $1,155,461.68
2080 $8,140,611.81 6.51 $1,250,399.41
2081 $8,791,860.76 6.50 $1,353,137.64
2082 $9,495,209.62 6.48 $1,464,317.29
2083 $10,254,826.39 6.47 $1,584,631.93
2084 $11,075,212.50 6.46 $1,714,832.15
2085 $11,961,229.50 6.45 $1,855,730.19
2086 $12,918,127.86 6.43 $2,008,205.01
2087 $13,951,578.09 6.42 $2,173,207.83
2088 $15,067,704.33 6.41 $2,351,767.99
2089 $16,273,120.68 6.39 $2,544,999.43
2090 $17,574,970.33 6.38 $2,754,107.60
2091 $18,980,967.96 6.37 $2,980,397.00
2092 $20,499,445.40 6.36 $3,225,279.32
2093 $22,139,401.03 6.34 $3,490,282.23
2094 $23,910,553.11 6.33 $3,777,058.92
2095 $25,823,397.36 6.32 $4,087,398.43
2096 $27,889,269.15 6.31 $4,423,236.78
2097 $30,120,410.68 6.29 $4,786,669.06
2098 $32,530,043.54 6.28 $5,179,962.51
2099 $35,132,447.02 6.27 $5,605,570.66
2100 $37,943,042.78 6.25 $6,066,148.61
2101 $40,978,486.20 6.24 $6,564,569.63
2102 $44,256,765.10 6.23 $7,103,943.09

Even so, EARTH population DECLINES dramatically to 600 millions;

Year Earth Off-world Light Years Stars Density/Star
2051 6.62 0.28 0.33 1 0.276
2052 6.36 0.53 0.67 1 0.527
2053 6.10 0.77 1.00 1 0.768
2054 5.86 1.00 1.33 1 0.998
2055 5.63 1.22 1.67 1 1.219
2056 5.40 1.43 2.00 1 1.430
2057 5.18 1.63 2.33 1 1.633
2058 4.98 1.83 2.67 1 1.826
2059 4.78 2.01 3.00 1 2.012
2060 4.59 2.19 3.33 1 2.189
2061 4.40 2.36 3.67 1 2.359
2062 4.23 2.52 4.00 1 2.522
2063 4.06 2.68 4.33 3 0.892
2064 3.90 2.83 4.67 3 0.942
2065 3.74 2.97 5.00 3 0.990
2066 3.59 3.10 5.33 3 1.035
2067 3.45 3.24 5.67 3 1.078
2068 3.31 3.36 6.00 4 0.840
2069 3.18 3.48 6.33 4 0.870
2070 3.05 3.59 6.67 4 0.898
2071 2.93 3.70 7.00 4 0.925
2072 2.81 3.80 7.33 4 0.951
2073 2.70 3.90 7.67 4 0.976
2074 2.59 4.00 8.00 5 0.800
2075 2.49 4.09 8.33 7 0.584
2076 2.39 4.18 8.67 8 0.522
2077 2.29 4.26 9.00 8 0.532
2078 2.20 4.34 9.33 8 0.542
2079 2.11 4.41 9.67 9 0.490
2080 2.03 4.48 10.00 9 0.498
2081 1.95 4.55 10.33 10 0.455
2082 1.87 4.62 10.67 11 0.420
2083 1.79 4.68 11.00 14 0.334
2084 1.72 4.74 11.33 18 0.263
2085 1.65 4.79 11.67 23 0.208
2086 1.59 4.85 12.00 24 0.202
2087 1.52 4.90 12.33 27 0.181
2088 1.46 4.94 12.67 29 0.170
2089 1.40 4.99 13.00 31 0.161
2090 1.35 5.03 13.33 32 0.157
2091 1.29 5.07 13.67 33 0.154
2092 1.24 5.11 14.00 36 0.142
2093 1.19 5.15 14.33 39 0.132
2094 1.14 5.19 14.67 42 0.123
2095 1.10 5.22 15.00 45 0.116
2096 1.06 5.25 15.33 49 0.107
2097 1.01 5.28 15.67 52 0.101
2098 0.97 5.31 16.00 56 0.095
2099 0.93 5.33 16.33 59 0.090
2100 0.90 5.36 16.67 63 0.085
2101 0.86 5.38 17.00 67 0.081
2102 0.83 5.40 17.33 71 0.076
2103 0.79 5.42 17.67 75 0.072
2104 0.76 5.44 18.00 79 0.069
2105 0.73 5.46 18.33 84 0.065
2106 0.70 5.48 18.67 88 0.062
2107 0.67 5.49 19.00 93 0.059
2108 0.65 5.51 19.33 98 0.056
2109 0.62 5.52 19.67 103 0.053
2110 0.60 5.54 20.00 109 0.051

These stars are from actual surveys out to 20 light years.

The important point is that Earth's population in 2110 is still 600
million people - and even though 5.54 billions are off-world, average
per star is only 51 millions! So, an aggressive program of expansion
beyond Earth would not allow populations to accumulate to a level that
would be of military concerns to those remaining on Earth within the
solar system.

That is, the Earth will continue to militarily dominate interstellar
affairs - which should ease the concerns of some who worry about this
possibility.

Dr. Von Braun actually may have set space colonization back a century
by writing his classified PhD thesis for the German high command back
in the 1930s. Here he described how someone who had a permanent base
on the moon, with self sufficient industrial infrastructure to build
rockets could bombard the Earth at will and with this threat and
beyond the means of Earth to retaliate (its much harder to go to the
moon than return from the moon - look at the size of the Apollo rocket
and the LEM) control the world.

This analysis also applies to Mars, and development of the asteroids
in-situ. Not so much to Venus due to its size, or the outer planets
or Mercury, due to the enrgetics and timing of things.

vonBraun's analysis fails completely beyond the Sun. The energy and
resources it takes to span the distance between the stars is large
compared to the success of any military campaign. So, we're safe
again - if we can keep control of developments.

This is achieved by;

(1) capturing rich asteroids and processing them in Earth orbit using
telerobotics;
(2) using solar pumped lasers to propel spaceships from star to star,
and across the solar system, and maintaining control of those lasers;
(3) promoting expansion beyond the solar system so no populations
accumulate around sol

vonBraun's paper remained classified until after 1960s. So, it MUST
have figured prominently in the creation of the OST and missile
proliferation planning of the era prior to that time.

So, this is why I take special care to address this specific
concern.

Using weapons grade fissile materials to build triggers for fusion
pulse spaceships that capture rich asteroids and bringing them into
Earth orbit, and raise industrial satellties - to process those
asteroids by solar powered tele-operated industry and distributed to
everyone on Earth - and allowing everyone on Earth to be employed tele-
robotically from anywhere - resolves many of the issues facing
humanity today. Including deflecting dangerous asteroids away from
Earth or into safe stable orbits.

This, along with power satellites, and global wireless hotspot, is the
first step along a path that leads to the stars relatively quickly.

Building space colonies on orbit from captured asteroids, moving those
colonies across the solar system, with solar pumped lasers, orbiting
close in to the sun, and then beyond the solar system, using laser
light sails, provides a means to move people off-world and out of the
solar system to the stars beyond.

Even at 1/3 light speed - we have the possibility before the end of
the 21st century - of reducing Earth's population to less than 600
millions and the average population per star system to less than 50
millions.

Beyond 2110 - assuming continuous expansion at 1/3 light speed - we
reach 200 light year radius in 600 years - in 2650 (we started in 2050
according to the projections). At that point we have the following
figures;

Number of Stars: 108,808
Number of People: 2.07 billions

Which is 19,025 people per star on average and each person .

200 light years is only 1/1,000th the span of the Milky Way!

Another point: At 8% economic growth;

Wealth: 1e+20 times 2050AD income per capita.

Which means each person makes 1 million times more money than the
ENTIRE WORLD makes today. Which doesn't seem possible to us here on
Earth, but to those surrounded by the resources of the cosmos, and
beneficiaries of advanced self-replicating machine systems informed by
super-human AI, whatever they can imagine, they will have. Its
imagining it that will be the issue - which is far different than the
world we face today - where our imaginations are constrained from
birth - for our own good! lol. (it is our abject lack of imagination
that is causing most of our problems today)

As our densities fall, and our population falls, combined with rising
living standards we may at the end of the 21st century build upon the
successful sequencing of the human genome at the end of the 20th
century - by using forensic data - including genetic data gathered
from forensic sources - to RE-CREATE people. Since birth rates are
below replacement level, and wealth is tremendous, challenges are
likely to be tremendous as well. So, re-creating people who have
lived before using genetic engineering, will be appealing from a
sociology and industrial perspective.

Just as ecologies benefit from biological diversity - so too do well
functioning societies benefit from social and biological diversity.

If we get really good at things, our population will not decline - no
one will die - and we will recreate EVERYONE that has lived before -
which will put our population - both natural and synthetics - at 19
billions. Artificials (AI) will grow without bound. This may be an
area of friction if mismanaged - especially as they get smarter than
us.

Even so, the fundamentals won't change. Even AI will expand into a
very large cosmos and see its population density fall.

So, what I'm saying is that even in 600 years we may have 20 billions
- of which 18 billions would be synthetics reconstructed from forensic
data - 2 billions would be naturals - and likely 2 trillions of super-
human AI serving the biologicals - but mostly tending to their own
interests after fulfilling their programming.

Even in this scenario, in 600 years, there are fewer people PER STAR
SYSTEM than live in Dayton Ohio today. As we expand outward, these
densities will fall.

At some point we will create superluminal travel - which is the same
as saying we can travel through time. The simplest way to achieve
this is to send a signal or object to the super-massive black hole at
the center of our galaxy. If we are lucky, it is spinning fast enough
to have time-violating regions -so closed time like loops are
possible. This means a signal can be sent to the supermassive black
hole and it arrives 30,000 years after being sent. It enters a CTL
and emerges 60,000 years before it arrives. It then is broadcast and
is received by a radio telescope at a distant star the moment it was
sent. A similar arrangement at a distant star allows instant
communication.

Or communication through time.

Replace the signals with spacecraft that move very near the speed of
light - and you can travel instantly anywhere.

Replace the supermassive black hole at the center of the galaxy with
custom built engineered black holes and you can do this more
conveniently.

Moving anywhere instantly - and anywhen.

Where do we get black holes?

Shaped masses of iron-56 when collided at 1/3 light speed - can be
made to form black holes.

You can do this with arrays of solar pumped lasers large enough to
drive starships from star to star.

Once you have a collection of engineered black holes, it may be
possible to cause them to interact in such a way as to cause decay of
the vacuum - to create other black holes - a self replicating black
hole machine.

If that's possible, then we will have created a new class of
engineered product. Not one based on crude matter - but one based on
charged, spinning, massive points of matter that distort spacetime in
controlled ways - and allow creation of time machines which give us
instant access across the cosmos to ALL OF SPACE AND TIME!

This is likely to happen well before we reach 200 light years from
Earth - well before 600 years from the present day. When it happens,
if it is possible at all, our densities will drop even faster than
reflected in the charts above!

That is, if our speed jumps from 1/3 light speed before 2650 to
infinity - our range of habitation rises from 108,808 stars within 200
light years of Earth to the 40,000 billion billion star systems in the
cosmos - at ANY TIME spanning the 1,000 billion years of interest to
intelligence!

THIS EXPLAINS THE FERMI PARADOX.

Even with 20 billions of us - and 2 trillion super-human AI - there
are 20 trillion star systems per person - and a trillion years within
each star system to play in.

The odds of finding anyone anywhere with this sort of technology - is
nearly non-existent - even if everyone everywhere - has this sort of
technology.

William Mook writes:

On Jan 5, 9:09Â*pm, David Spain wrote:
David Spain writes:
As opposed to:

V(n+1) = (aV(n) + c) mod m

whe

m 0
0 a m
0 = c m
0 = Vo m Â*(and if c=0, Vo 0) --

FYI, this is wrong, if c=0, Vo must be co-prime to m.

Sorry.

;-)

Dave

The growth factor leading to exponential growth in my original Jan 2
post was based on organic or natural feedback that is known to occur
in nature/society/industry.

What is the natural or organic process that leads inevitably to the
modulo function you claim here? Unintended consequences? Resource
depletion? How does that work? I presume you don't need to know how
exponential growth works in an infinite field of resources right?


To William Mook: please ignore this post.
To the rest of the group: ;-)

Dave

David Spain wrote:
To William Mook: please ignore this post.
To the rest of the group: ;-)

I'm still trying to figure out that wheelbarrow Tony Lance keeps going
on about that has the wheel in the wrong place.
You had better do some math on that also.

Pat

On Dec 18 2009, 4:43*am, "Androcles"
wrote:
"Jonathan" wrote in message

news
I like this idea, *Relatively small mirrors would power
the lasers, not huge solar cell arrays. The lasers would
transmit their beams to other satellites that convert it to, and
beam it down, as microwaves. * No need for mile-size
collectors in orbit.

What are you babbling about?

I can't be certain, but I will say that if you move a solar collector
array closer to the sun it will gather more energy for a given size.
For example, something only 3 million km from the solar center will be
1/50th the distance from the sun as the Earth. So, solar intensity is
2,500x greater than at Earth orbit. That's 3.45 megawatts per square
meter. So, to intercept 17 TW of power requires less than 5 square km
of area. At 33% overall efficiency that's 15 sq km.
Using solar power to sail a power satellite to the sun. Something
only 4.4 km in diameter - to power the WHOLE EARTH!

A 4.4 km diameter laser emitter is capable of forming a spot less than
41.6 meters across at Earth Orbit using 1,000 nm wavelength light.

A 400 meter diameter system (1/10th the diam) produces 170 GW (1/100th
the power) and forms a spot reliably 400 meters across (1/10th the
angular resolution). 20 of these satellites would power the entire
Earth. 10 at sol, 10 at GEO.

25,000 comparably sized satellites would be needed to do it all at
GEO.

Since we can use sunlight to propel satellites toward the sun fairly
efficiently, once they're on orbit, this is something we can consider
doing today.

170 GW at $0.043 per kWh generates $7.31 million per hour. That's
$64 billion per year. $12.8 trillion over 20 years.

Compare this to $2,924 per hour and $25.6 million per year and $512
million over 20 years.

The first satellite pays for the entire program to build it from
scratch. The second satellite which is the same size and cost barely
pays for launch cost.

Androcles wrote:

I can't be certain, but I will say that if you move a solar collector
array closer to the sun it will gather more energy for a given size.

The only place you could do that at and have it stay in the same place
in relation to the Earth would be the Earth/Sun L-1 Lagrangian
point...which isn't stable:
http://www.tau.ac.il/~morris/0341120...nge_Points.htm

Pat