I did some maths a few months back. I got some answers that surprised
me. I then checked out the Fresh Look study for SPS, and there were
some notes that agreed with my analysis.

It looks like Solar Power Sats are actually economic, with no need for
lunar launch infrastructure.

Basically, I took a Falcon I, and asked- how often could I launch it?
Then I did the maths, and extrapolated the economies of scale on the
hardware and launch infrastructure of the Falcon I.

The launch costs fell below about $500/kg which is reckoned to be the
breakeven cost for SPS to be viable.

I then did a similar thing for solar panels.

Result: Energy costs of about $0.05/kWh for 4 4GW SPS; dropping lower
if you build multiple stations.

This assumes very high launch rates however- dozens of launches per
day. Analysis of the Falcon I suggests that it may be possible (it's
not dissimilar to a V2 in size, and the Germans managed quite a lot of
launches per day; so it's not totally without precedent and it seems
likely the same techniques would work for the Falcon I.)

The economics get even better if you use Russian launchers or
something (Chinese :-) or Indian labour); because the cost of labour
is much lower...

The downside is that it doesn't involve launching any people at all.
The upside is that it would cause the launch costs to plummet and that
in itself can open space.

-Ian Woollard

"People are brilliantly stupid, and stupidly brilliant"-Robin Abrahams

I haven't checked out the details at all, but relatively small-scale
SPS without colonies sounds plausible at first glance. (By
relatively small scale, I mean compared to the terawatts of global
demand.)

But first SPS has to beat ground-based solar. I'm dubious that the
factor of four gained from full-strength sunlight 24-7 is enough to
outweigh launch costs, unless we can get by with launching only a
small fraction of the mass and using space resources for the rest.
The amount of area on the ground isn't a real problem in the medium
term: it's less than we already have paved.

--- In spacesettlers@yahoogroups.com, Ian Woollard
wrote:
>
> I did some maths a few months back. I got some answers that
surprised
> me. I then checked out the Fresh Look study for SPS, and there were
> some notes that agreed with my analysis.
>
> It looks like Solar Power Sats are actually economic, with no need
for
> lunar launch infrastructure.
>
> Basically, I took a Falcon I, and asked- how often could I launch
it?
> Then I did the maths, and extrapolated the economies of scale on
the
> hardware and launch infrastructure of the Falcon I.
>
> The launch costs fell below about $500/kg which is reckoned to be
the
> breakeven cost for SPS to be viable.
>
> I then did a similar thing for solar panels.
>
> Result: Energy costs of about $0.05/kWh for 4 4GW SPS; dropping
lower
> if you build multiple stations.
>
> This assumes very high launch rates however- dozens of launches per
> day. Analysis of the Falcon I suggests that it may be possible
(it's
> not dissimilar to a V2 in size, and the Germans managed quite a
lot of
> launches per day; so it's not totally without precedent and it
seems
> likely the same techniques would work for the Falcon I.)
>
> The economics get even better if you use Russian launchers or
> something (Chinese :-) or Indian labour); because the cost of
labour
> is much lower...
>
> The downside is that it doesn't involve launching any people at
all.
> The upside is that it would cause the launch costs to plummet and
that
> in itself can open space.
>
> --
> -Ian Woollard
>
> "People are brilliantly stupid, and stupidly brilliant"-Robin
Abrahams

I found when I did the arithmetic, the projected costs of the panels
and the launch costs worked out very roughly the same. So the costs
seem lower than terrestial *and* more reliable.

In addition, the economies of scale that you inevitably get on the
panels is good too.

On 11/3/05, Dan Wylie-Sears wrote:
> I haven't checked out the details at all, but relatively small-scale
> SPS without colonies sounds plausible at first glance. (By
> relatively small scale, I mean compared to the terawatts of global
> demand.)
>
> But first SPS has to beat ground-based solar. I'm dubious that the
> factor of four gained from full-strength sunlight 24-7 is enough to
> outweigh launch costs, unless we can get by with launching only a
> small fraction of the mass and using space resources for the rest.
> The amount of area on the ground isn't a real problem in the medium
> term: it's less than we already have paved.
>
> --- In spacesettlers@...m, Ian Woollard
> wrote:
> >
> > I did some maths a few months back. I got some answers that
> surprised
> > me. I then checked out the Fresh Look study for SPS, and there were
> > some notes that agreed with my analysis.
> >
> > It looks like Solar Power Sats are actually economic, with no need
> for
> > lunar launch infrastructure.
> >
> > Basically, I took a Falcon I, and asked- how often could I launch
> it?
> > Then I did the maths, and extrapolated the economies of scale on
> the
> > hardware and launch infrastructure of the Falcon I.
> >
> > The launch costs fell below about $500/kg which is reckoned to be
> the
> > breakeven cost for SPS to be viable.
> >
> > I then did a similar thing for solar panels.
> >
> > Result: Energy costs of about $0.05/kWh for 4 4GW SPS; dropping
> lower
> > if you build multiple stations.
> >
> > This assumes very high launch rates however- dozens of launches per
> > day. Analysis of the Falcon I suggests that it may be possible
> (it's
> > not dissimilar to a V2 in size, and the Germans managed quite a
> lot of
> > launches per day; so it's not totally without precedent and it
> seems
> > likely the same techniques would work for the Falcon I.)
> >
> > The economics get even better if you use Russian launchers or
> > something (Chinese :-) or Indian labour); because the cost of
> labour
> > is much lower...
> >
> > The downside is that it doesn't involve launching any people at
> all.
> > The upside is that it would cause the launch costs to plummet and
> that
> > in itself can open space.
> >
> > --
> > -Ian Woollard
> >
> > "People are brilliantly stupid, and stupidly brilliant"-Robin
> Abrahams
> >

-Ian Woollard

"People are brilliantly stupid, and stupidly brilliant"-Robin Abrahams

What orbit would these units have?

Ian Woollard wrote:I found when I did the arithmetic, the projected costs of the panels
and the launch costs worked out very roughly the same. So the costs
seem lower than terrestial *and* more reliable.

In addition, the economies of scale that you inevitably get on the
panels is good too.

On 11/3/05, Dan Wylie-Sears wrote:
> I haven't checked out the details at all, but relatively small-scale
> SPS without colonies sounds plausible at first glance. (By
> relatively small scale, I mean compared to the terawatts of global
> demand.)
>
> But first SPS has to beat ground-based solar. I'm dubious that the
> factor of four gained from full-strength sunlight 24-7 is enough to
> outweigh launch costs, unless we can get by with launching only a
> small fraction of the mass and using space resources for the rest.
> The amount of area on the ground isn't a real problem in the medium
> term: it's less than we already have paved.
>
> --- In spacesettlers@yahoogroups.com, Ian Woollard
> wrote:
> >
> > I did some maths a few months back. I got some answers that
> surprised
> > me. I then checked out the Fresh Look study for SPS, and there were
> > some notes that agreed with my analysis.
> >
> > It looks like Solar Power Sats are actually economic, with no need
> for
> > lunar launch infrastructure.
> >
> > Basically, I took a Falcon I, and asked- how often could I launch
> it?
> > Then I did the maths, and extrapolated the economies of scale on
> the
> > hardware and launch infrastructure of the Falcon I.
> >
> > The launch costs fell below about $500/kg which is reckoned to be
> the
> > breakeven cost for SPS to be viable.
> >
> > I then did a similar thing for solar panels.
> >
> > Result: Energy costs of about $0.05/kWh for 4 4GW SPS; dropping
> lower
> > if you build multiple stations.
> >
> > This assumes very high launch rates however- dozens of launches per
> > day. Analysis of the Falcon I suggests that it may be possible
> (it's
> > not dissimilar to a V2 in size, and the Germans managed quite a
> lot of
> > launches per day; so it's not totally without precedent and it
> seems
> > likely the same techniques would work for the Falcon I.)
> >
> > The economics get even better if you use Russian launchers or
> > something (Chinese :-) or Indian labour); because the cost of
> labour
> > is much lower...
> >
> > The downside is that it doesn't involve launching any people at
> all.
> > The upside is that it would cause the launch costs to plummet and
> that
> > in itself can open space.
> >
> > --
> > -Ian Woollard
> >
> > "People are brilliantly stupid, and stupidly brilliant"-Robin
> Abrahams
> >

-Ian Woollard

"People are brilliantly stupid, and stupidly brilliant"-Robin Abrahams

Panels costing $500/kg after the economies of scale kick in? Sounds
kind of steep. What interest rate did you assume in order to come
up with the price of power?

Note that groundbound solar can also be thermal, either convective
or steam-turbine. Either one takes care of the nighttime issue by
just having some thermal mass to store the heat. Convective thermal
solar probably works better at night, because of the lower
temperature at the outflow.

How do you figure the part about "more reliable"? If a system on
the ground gets a glitch, you drive around in a truck to find it and
fix it. If a bit of space junk hits the wrong wire, what do you
do? And how much did you budget for maintenance, in order to get
higher reliability than can be achieved with maintenance and repair
workers commuting on wheels?

Matt Gallimore makes a good point about the orbit. Launch costs are
usually quoted to LEO, but LEO puts you in the dark part of the
time, plus satellites in LEO catch a few stray air molecules and
occasionally need to reboost a little. But if you go to a higher
delta V orbit, you need to pay the rocket equation.

--- In spacesettlers@yahoogroups.com, Ian Woollard
wrote:
>
> I found when I did the arithmetic, the projected costs of the
panels
> and the launch costs worked out very roughly the same. So the costs
> seem lower than terrestial *and* more reliable.
>
> In addition, the economies of scale that you inevitably get on the
> panels is good too.
>
> On 11/3/05, Dan Wylie-Sears wrote:
> > I haven't checked out the details at all, but relatively small-
scale
> > SPS without colonies sounds plausible at first glance. (By
> > relatively small scale, I mean compared to the terawatts of
global
> > demand.)
> >
> > But first SPS has to beat ground-based solar. I'm dubious that
the
> > factor of four gained from full-strength sunlight 24-7 is enough
to
> > outweigh launch costs, unless we can get by with launching only a
> > small fraction of the mass and using space resources for the
rest.
> > The amount of area on the ground isn't a real problem in the
medium
> > term: it's less than we already have paved.
> >
> > --- In spacesettlers@yahoogroups.com, Ian Woollard
> > wrote:
> > >
> > > I did some maths a few months back. I got some answers that
> > surprised
> > > me. I then checked out the Fresh Look study for SPS, and there
were
> > > some notes that agreed with my analysis.
> > >
> > > It looks like Solar Power Sats are actually economic, with no
need
> > for
> > > lunar launch infrastructure.
> > >
> > > Basically, I took a Falcon I, and asked- how often could I
launch
> > it?
> > > Then I did the maths, and extrapolated the economies of scale
on
> > the
> > > hardware and launch infrastructure of the Falcon I.
> > >
> > > The launch costs fell below about $500/kg which is reckoned to
be
> > the
> > > breakeven cost for SPS to be viable.
> > >
> > > I then did a similar thing for solar panels.
> > >
> > > Result: Energy costs of about $0.05/kWh for 4 4GW SPS; dropping
> > lower
> > > if you build multiple stations.
> > >
> > > This assumes very high launch rates however- dozens of
launches per
> > > day. Analysis of the Falcon I suggests that it may be possible
> > (it's
> > > not dissimilar to a V2 in size, and the Germans managed quite a
> > lot of
> > > launches per day; so it's not totally without precedent and it
> > seems
> > > likely the same techniques would work for the Falcon I.)
> > >
> > > The economics get even better if you use Russian launchers or
> > > something (Chinese :-) or Indian labour); because the cost of
> > labour
> > > is much lower...
> > >
> > > The downside is that it doesn't involve launching any people at
> > all.
> > > The upside is that it would cause the launch costs to plummet
and
> > that
> > > in itself can open space.
> > >
> > > --
> > > -Ian Woollard
> > >
> > > "People are brilliantly stupid, and stupidly brilliant"-Robin
> > Abrahams
> > >
> --
> -Ian Woollard
>
> "People are brilliantly stupid, and stupidly brilliant"-Robin
Abrahams

What of the cost of the ground based receiving station?

The operation and maintanence staffing of that facility also is part of the equation...

Now as for the LEO orbit, I've given this a little thought (stress LITTLE). LEO orbit for SPS is, basically, useless.

We now have thin film photoelectic materials. From what I have read we will soon have spray on (few microns thick) materials that would serve the same purpose as our solar panels. Now, if these materials were able to withstand the environment of space, I can concieve of a way that this would make economic sense for LEO launching....

Instead of a large SPS, how about a fleet of large, though wispy thin ones? If we launch a mass to LEO and it unfolds itself, we could design a device that has two surfaces, one with highly reflective properties and one that can convert solar to eletricity. This large semicircular wings would unfold around a very small central satellite. Being really thin, orient the reflective surfaces to the sun and utilize the wings / solar cells as a solar sail. In this orientation the satellite could ascend, slowly, to a higher orbit, even GEO. At the desired orbit, the satellite can turn and have the solar-electric conversion side of the wings facing the sun.

There would then be a small SPS in a desired orbit, launched only to GEO.

Complicating factor is no very large solar sail has been used yet. That and the unfolding mechanism could be complex. On the plus side, this would, for a rather small weight, yield a lot of surface area.

I wouldn't see this as benefiting a city. A small SPS is best for remote industrial activities or remote communities.

If this is viable, then after a lot of these are in orbit... someone might develop a viable business model for space maintanence. At that point a lot of other interesting things might develop.

Dan Wylie-Sears wrote:
Panels costing $500/kg after the economies of scale kick in? Sounds
kind of steep. What interest rate did you assume in order to come
up with the price of power?

Note that groundbound solar can also be thermal, either convective
or steam-turbine. Either one takes care of the nighttime issue by
just having some thermal mass to store the heat. Convective thermal
solar probably works better at night, because of the lower
temperature at the outflow.

How do you figure the part about "more reliable"? If a system on
the ground gets a glitch, you drive around in a truck to find it and
fix it. If a bit of space junk hits the wrong wire, what do you
do? And how much did you budget for maintenance, in order to get
higher reliability than can be achieved with maintenance and repair
workers commuting on wheels?

Matt Gallimore makes a good point about the orbit. Launch costs are
usually quoted to LEO, but LEO puts you in the dark part of the
time, plus satellites in LEO catch a few stray air molecules and
occasionally need to reboost a little. But if you go to a higher
delta V orbit, you need to pay the rocket equation.

--- In spacesettlers@yahoogroups.com, Ian Woollard
wrote:
>
> I found when I did the arithmetic, the projected costs of the
panels
> and the launch costs worked out very roughly the same. So the costs
> seem lower than terrestial *and* more reliable.
>
> In addition, the economies of scale that you inevitably get on the
> panels is good too.
>
> On 11/3/05, Dan Wylie-Sears wrote:
> > I haven't checked out the details at all, but relatively small-
scale
> > SPS without colonies sounds plausible at first glance. (By
> > relatively small scale, I mean compared to the terawatts of
global
> > demand.)
> >
> > But first SPS has to beat ground-based solar. I'm dubious that
the
> > factor of four gained from full-strength sunlight 24-7 is enough
to
> > outweigh launch costs, unless we can get by with launching only a
> > small fraction of the mass and using space resources for the
rest.
> > The amount of area on the ground isn't a real problem in the
medium
> > term: it's less than we already have paved.
> >
> > --- In spacesettlers@yahoogroups.com, Ian Woollard
> > wrote:
> > >
> > > I did some maths a few months back. I got some answers that
> > surprised
> > > me. I then checked out the Fresh Look study for SPS, and there
were
> > > some notes that agreed with my analysis.
> > >
> > > It looks like Solar Power Sats are actually economic, with no
need
> > for
> > > lunar launch infrastructure.
> > >
> > > Basically, I took a Falcon I, and asked- how often could I
launch
> > it?
> > > Then I did the maths, and extrapolated the economies of scale
on
> > the
> > > hardware and launch infrastructure of the Falcon I.
> > >
> > > The launch costs fell below about $500/kg which is reckoned to
be
> > the
> > > breakeven cost for SPS to be viable.
> > >
> > > I then did a similar thing for solar panels.
> > >
> > > Result: Energy costs of about $0.05/kWh for 4 4GW SPS; dropping
> > lower
> > > if you build multiple stations.
> > >
> > > This assumes very high launch rates however- dozens of
launches per
> > > day. Analysis of the Falcon I suggests that it may be possible
> > (it's
> > > not dissimilar to a V2 in size, and the Germans managed quite a
> > lot of
> > > launches per day; so it's not totally without precedent and it
> > seems
> > > likely the same techniques would work for the Falcon I.)
> > >
> > > The economics get even better if you use Russian launchers or
> > > something (Chinese :-) or Indian labour); because the cost of
> > labour
> > > is much lower...
> > >
> > > The downside is that it doesn't involve launching any people at
> > all.
> > > The upside is that it would cause the launch costs to plummet
and
> > that
> > > in itself can open space.
> > >
> > > --
> > > -Ian Woollard
> > >
> > > "People are brilliantly stupid, and stupidly brilliant"-Robin
> > Abrahams
> > >
> --
> -Ian Woollard
>
> "People are brilliantly stupid, and stupidly brilliant"-Robin
Abrahams

On 11/3/05, Dan Wylie-Sears wrote:
> Panels costing $500/kg after the economies of scale kick in? Sounds
> kind of steep.

Well, I used 3kW per kilogram.

> What interest rate did you assume in order to come
> up with the price of power?

I plumped about 8%. Rather optimistic really.

> How do you figure the part about "more reliable"?

I meant more reliable due to lack of weather. Reliability of SPS is
impossible to predict a priori.

> If a bit of space junk hits the wrong wire, what do you
> do? And how much did you budget for maintenance, in order to get
> higher reliability than can be achieved with maintenance and repair
> workers commuting on wheels?

I simply assumed that a percentage of the panels failed every year. To
be honest, the space environment isn't particularly hostile, by and
large. It's quite possible to build-in enough redundancy upfront that
nothing really huge would fail I think.

The only thing that really scares me is the Sun. A huge solar flare
could be nasty...

> Matt Gallimore makes a good point about the orbit. Launch costs are
> usually quoted to LEO, but LEO puts you in the dark part of the
> time, plus satellites in LEO catch a few stray air molecules and
> occasionally need to reboost a little. But if you go to a higher
> delta V orbit, you need to pay the rocket equation.

Yes, I factored that in.

-Ian Woollard

"People are brilliantly stupid, and stupidly brilliant"-Robin Abrahams

On 11/3/05, Ian Woollard wrote:
> Well, I used 3kW per kilogram.

Oops. I mean 3kg/Kw.

> --
> -Ian Woollard
>
> "People are brilliantly stupid, and stupidly brilliant"-Robin Abrahams

-Ian Woollard

"People are brilliantly stupid, and stupidly brilliant"-Robin Abrahams

> From: Dan Wylie-Sears
> Panels costing $500/kg after the economies of scale kick in?

It's hard to get any idea of what high performance solar panels will cost.
Remember though, that earth bound solar panels are made very thick or given
hard backing material to make them durable. This would not be required in
space, and would significantly reduce cost/area or cost/wattage - which is a
more accurate measure of cost than weight.

> Either one takes care of the nighttime issue by
> just having some thermal mass to store the heat.

I'm pretty sure the laws of thermodynamics would stop you from being able to
store, say, a few million gallons of high temperature steam without loosing
significant amounts of energy. Ground based thermal power plants make more
sense from that point of view.

> If a bit of space junk hits the wrong wire, what do you do?

That's a silly question. If we're building these things on a commercial
basis then we have a crew of hundreds/thousands in geo orbit putting the
things together. A space taxi with a deltaV of 2kmps can get from one side
of GSO to the other in about 1.5 days and back again in the same period.
Besides which, where ever possible SPSs would be built so that a single wire
couldn't knock them out.

> And how much did you budget for maintenance, in order to get
> higher reliability than can be achieved with maintenance and repair
> workers commuting on wheels?

Let's see:
Cost of fixing global warming caused by those 'wheels'.
Cost of environmental erosion on the array
Cost of cleaning up localised environmental contamination.
Cost of not setting up misc space industries by not developing low cost
launch capacity.

> But if you go to a higher
> delta V orbit, you need to pay the rocket equation.

There are no commercial figures for nuclear or solar ion propulsion.
Especially on a large scale. Since this is the method most SPS builders
advocate they do naturally ignore the wasteful and small scale costs of
chemical rockets.

John

Dan Wylie-Sears wrote:

> Note that groundbound solar can also be thermal, either convective
> or steam-turbine. Either one takes care of the nighttime issue by
> just having some thermal mass to store the heat. Convective thermal
> solar probably works better at night, because of the lower
> temperature at the outflow.

SSPS can be solar thermal. Thin film metal mirror focused on a Brayton
or Stirling Cycle engine. (eg: http://www.lgarde.com/programs/powant.html)

As for launching dozens of Falcons a day, why not launch one or two Sea
Dragon type vehicles. 500+ tonnes per launch to LEO. falcon 5 would only
put 4 tonnes in the same orbit.

If you don't want to send a lesser amount to GEO, then develop a tug to
take the cargo to higher orbit using O2 or similar as the fuel and put a
few tonnes of fuel in each launch for the tug, at 500+ tonnes for
payload a couple of tonnes of fuel for the tug isn't going to cause many
problems.

Someone mentioned Solar Flares. I wonder which is more robust in that
situation Solar Panels, or Solar Thermal. I am guessing that with Solar
thermal there would be less electronic components, so they might be
easier to provide shielding for.

Brett

From: spacesettlers@yahoogroups.com
[mailto:spacesettlers@yahoogroups.com] On Behalf Of b

> SSPS can be solar thermal. Thin film metal mirror focused
> on a Brayton or Stirling Cycle engine.

And in fact, O'Neill once made the point that the reason why solar
thermal gets excluded from so many SPS studies is because of the greater
weight. But if making SPS from space materials, weight becomes a lesser
consideration.

Thermal would certainly beat PV for efficiency. I worry about
maintenance, though.

Regards,

Mike Combs

Indeed SPS can be thermal. But my point in mentioning thermal was
that it addresses day/night concerns about ground-based solar, and
of course SPS don't have that issue to begin with.

--- In spacesettlers@yahoogroups.com, "Combs, Mike"
>
> From: spacesettlers@yahoogroups.com
> [mailto:spacesettlers@yahoogroups.com] On Behalf Of b
>
> > SSPS can be solar thermal. Thin film metal mirror focused
> > on a Brayton or Stirling Cycle engine.
>
> And in fact, O'Neill once made the point that the reason why solar
> thermal gets excluded from so many SPS studies is because of the
greater
> weight. But if making SPS from space materials, weight becomes a
lesser

Whether groundbased Solar is Thermal or PV or both, it still has the problem of
generating and storing (the expensive bit - even if you use thermal methods)
enough electricity for 24 hours off of approximately 5 peak hours of sunlight.

Brett

Quoting Dan Wylie-Sears :

--- In spacesettlers, bmaillists wrote:

> Whether groundbased Solar is Thermal or PV or both, it still has
> the problem of generating and storing (the expensive bit - even if
> you use thermal methods) enough electricity for 24 hours off of
> approximately 5 peak hours of sunlight.
>
> Brett

Ya know, I'm fond of saying that the problem with a ground-based solar
energy system is that it's dark half the time. I've even been known
to shout about it: ITS **DARK** HALF THE TIME!!!!! But the reality is
worse than that, isn't it? It's dark half the time, and semi-dark for
nearly half of what's left. The Earth isn't Edgar Rice Burroughs'
Pellucidar, not even half the time. It isn't night half the time and
noon the other half. For purposes of solar energy, the Earth sucks,
and that's in the daytime.

Storing the heat is not expensive. In the steam-turbine approach
it's a tank of molten salt; in the convection-tower approach it
literally costs nothing because it's the ground underneath. It
would be expensive for SPS because of all the mass it needs, but not
here where the ground is already underfoot anyway.

I want to see space developed, but launching the collection system
and the maintenance personnel and everything the maintenance
personnel need and the transmitter, plus paying for the rectenna on
the ground, just sounds a whole lot more expensive than painting,
roofing, and paving with PV instead of conventional paint, roof
tiles, and pavement, or choosing systems for low cost at the expense
of reliability (which you can do if the maintenance people are on-
site already, but not if they're $500+/kg away).

If it were launching just the collection systems, the factor of
about four (dark half the time, half-dark the other half) well might
cover it.

--- In spacesettlers@yahoogroups.com, bmaillists@i... wrote:
>
> Whether groundbased Solar is Thermal or PV or both, it still has
the problem of
> generating and storing (the expensive bit - even if you use
thermal methods)
> enough electricity for 24 hours off of approximately 5 peak hours
of sunlight.
>
> Brett
>
> Quoting Dan Wylie-Sears :
>
> > Indeed SPS can be thermal. But my point in mentioning thermal
was
> >
> > that it addresses day/night concerns about ground-based solar,
and
> >
> > of course SPS don't have that issue to begin with.
> >
> > --- In spacesettlers@yahoogroups.com, "Combs, Mike"

> >
> > wrote:
> >
> > > From: spacesettlers@yahoogroups.com
> >
> > > [mailto:spacesettlers@yahoogroups.com] On Behalf Of b
> >
> > > > SSPS can be solar thermal. Thin film metal mirror focused
> >
> > > > on a Brayton or Stirling Cycle engine.
> >
> > > And in fact, O'Neill once made the point that the reason why
solar
> >
> > > thermal gets excluded from so many SPS studies is because of
the
> >
> > greater
> >
> > > weight. But if making SPS from space materials, weight
becomes a
> >
> > lesser
> >
> > > consideration.
> >
> > > Thermal would certainly beat PV for efficiency. I worry about
> >
> > > maintenance, though.
> >
> > > Regards,
> >
> > > Mike Combs
> >
> > Science education
> >
> > Space exploration
> >
Service.

SPS doesn't require you to store heat or electricity in space. It's on 24 x 7
98% of the year (depending on orbit)

In Space for a thermal system you need the mirror, the engine, the transmitter.
For a PV system you need the Panels and the transmitter.

Brett

Quoting Dan Wylie-Sears :

On 11/4/05, Dan Wylie-Sears wrote:
> Storing the heat is not expensive. In the steam-turbine approach
> it's a tank of molten salt; in the convection-tower approach it
> literally costs nothing because it's the ground underneath. It
> would be expensive for SPS because of all the mass it needs, but not
> here where the ground is already underfoot anyway.

Yes, but for example, I live in the UK; which is a *long* way north
(rather *further* than Ottawa in Canada). During summertime solar
might work.

But during the winter; it rains. And rains. And rains and rains. And
it's dark; with 100% cloudcover for much of the time. Ground-level
solar doesn't really work at all. You simply can't store the heat for
months at a time.

Whereas SPS would work 24x365.25.

-Ian Woollard

"People are brilliantly stupid, and stupidly brilliant"-Robin Abrahams

I don't see that weight has to be that much of a problem. Cosmos 1 had a sail
made of 5 micron thin aluminized reinforced Mylar which covered 600 square
meters and weighed just 100 kg.

L'Garde (http://lgarde.com) has done quite a bit of work on Inflatable space
structures including Antennas and Thermal Power Systems. They estimate that a
700 m diameter antenna would weigh approx 50,000 pounds (22 tonnes)

There isn't much difference between an antenna and a mirror. What remains is
just how heavy a brayton cycle engine would be for a mirror that size.

The other problem is can mirrors of that size be manufactured on the ground in
mass production (at say the rate of 1 per day).

Brett

Quoting "Combs, Mike" :

Structures in space can be vastly lighter than in one gee, but there
are still tidal forces and the stresses of reboosting or
reorienting. At sizes like 600 square meters it's not much of an
issue, but at the sizes needed for SPS there will have to be some
structure.

--- In spacesettlers@yahoogroups.com, bmaillists@i... wrote:
>
> I don't see that weight has to be that much of a problem. Cosmos 1
had a sail
> made of 5 micron thin aluminized reinforced Mylar which covered
600 square
> meters and weighed just 100 kg.
>
> L'Garde (http://lgarde.com) has done quite a bit of work on
Inflatable space
> structures including Antennas and Thermal Power Systems. They
estimate that a
> 700 m diameter antenna would weigh approx 50,000 pounds (22 tonnes)
>
> There isn't much difference between an antenna and a mirror. What
remains is
> just how heavy a brayton cycle engine would be for a mirror that
size.
>
> The other problem is can mirrors of that size be manufactured on
the ground in
> mass production (at say the rate of 1 per day).
>
> Brett
>
> Quoting "Combs, Mike" :
>
> > From: spacesettlers@yahoogroups.com
> >
> > [mailto:spacesettlers@yahoogroups.com] On Behalf Of b
> >
> > > SSPS can be solar thermal. Thin film metal mirror focused
> >
> > > on a Brayton or Stirling Cycle engine.
> >
> > And in fact, O'Neill once made the point that the reason why
solar
> >
> > thermal gets excluded from so many SPS studies is because of the
greater
> >
> > weight. But if making SPS from space materials, weight becomes
a lesser
> >
> > consideration.
> >
> > Thermal would certainly beat PV for efficiency. I worry about
> >
> > maintenance, though.
> >
> > Regards,
> >
> > Mike Combs
> >
> > Science education
> >
> > History of space exploration
> >
> > Space exploration
> >
Service.

From: spacesettlers@yahoogroups.com
[mailto:spacesettlers@yahoogroups.com] On Behalf Of Dan Wylie-Sears

> Structures in space can be vastly lighter than in one gee,
> but there are still tidal forces and the stresses of reboosting
> or reorienting. At sizes like 600 square meters it's not much
> of an issue, but at the sizes needed for SPS there will have to
> be some structure.

True, but on a SPS, I'd anticipate that attitude control would be via
low-thrust/high-efficiency RCS like ion engines or Hall Effect
thrusters.

There should be no need for reboost at GEO altitude. Orbital decay is a
phenomena of LEO.

Regards,

Mike Combs

Satellites that orbit above 1,000 km (620 mi) will stay up there for
thousands of years.

So, there's really no need to go all the way to GEO (GEO= 35,800 km (about
22,200 mi)).

But for a sense of security and for giant and multiple structures and
complex space architecture intended to coexist in the long term, maybe L5
would be best.

For SPS though, maybe we don't want to go too far out.

George
http://www.cygo.com/

On 11/4/05, Combs, Mike wrote:

From: spacesettlers@yahoogroups.com
[mailto:spacesettlers@yahoogroups.com] On Behalf Of cygonaut

> Satellites that orbit above 1,000 km (620 mi) will stay up there for
thousands of years.
>
> So, there's really no need to go all the way to GEO (GEO= 35,800 km
(about 22,200 mi)).

No, the reason for placing SPS in GEO is so that they're stationary with
regard to the ground, which vastly simplifies pointing issues. (In
other words, the rectenna can be made from fixed panels.)

I was only making the point that once we get to the orbital altitude we
want (for other reasons), we're to an altitude where reboost shouldn't
be a requirement.

Regards,

Mike Combs

Thanks for pointing that out to me Mike.

I should've spent more time on that link I posted.

Like maybe actually reading it (-lol).

George

Structure, you mean like this http://www.lgarde.com/programs/irss.html ?

Take as many of those 700 m diameter mirror and engine modules as
needed, join them with inflatable rigidifiable structures that are pre
wired to handle the electrical output from the modules. Have them feed
through to the transmitter.

One thing I am not sure of is if you can do the transmitter with the
same inflatable materials though.

So, if your mirrors and structure are all lightweight and inflatable the
whole thing becomes a better prospect weight wise.

In regards to maintenance, the engines IIRC are sealed units. It should
be possible to make them easy to detach / reattach so you can swap them
out if needed.

Brett

Dan Wylie-Sears wrote:

"Dan Wylie-Sears" wrote:
> Storing the heat is not expensive. In the steam-turbine approach
> it's a tank of molten salt; in the convection-tower approach it
> literally costs nothing because it's the ground underneath.

Storing it for *long* periods of time, like during long rainy seasons,
might be. I've seen designs where the solar power electricity is used
to make methane, which *can* be stored for long periods of time, and
can be transported to anywhere for power generation when/where it is
needed.

I'm with you on the opinion that earth-based solar power is a better
idea than SPS, though.