[ExI] Written for another list

Tue Jul 31 22:25:53 UTC 2012

On Tue, Jul 31, 2012 at 12:00 PM, Keith Henson <hkeithhenson at gmail.com> wrote:
> Adrian Tymes <atymes at gmail.com> wrote:
>> On Mon, Jul 30, 2012 at 7:36 AM, Keith Henson <hkeithhenson at gmail.com> wrote:
>>> That's acceptable for powering
>>> lasers, but I can't see much of a market for multiple GW at 20 times
>>> the cost of electricity from nuclear plants.
>>
>> Nope.  If the cost of electricity is higher than what you get
>> off the grid, then it's not acceptable for powering lasers,
>> since you could just get it off the grid instead.
>
> That would be lovely.  Do you have any suggestions of how to draw 7 GW
> off the grid from GEO?

Ah, I thought you were talking groundside.

But if it's 20 times the cost of nuclear reactors in GEO,
then it's cheaper just to put nuclear reactors in GEO,
and the higher cost is still not acceptable even for
powering lasers.

> It is possible to send the laser beams up to GEO and bounce them from
> there down to the launch vehicle path some 4000 km along the equator.
> It may even be more economical because tracking mirrors should be
> lighter, but the risk factor of it not working due to atmospheric
> distortion is high.  After looking at alternatives, putting a first
> power plant and laser in GEO with conventional rockets looked to be
> the lower total cost and risk.  This is subject to further analysis.
> Want to do it?

No, because I don't buy your premise that it is not
practical to demonstrate this at a much lower scale.

>>> I can send you the spreadsheet for the financial model if you want to
>>> try making money on conventional propulsion.
>>
>> I might be interested in taking a look *if* your spreadsheet
>> includes the costs of the intermediate conventional
>> propulsion stage.  If it does not, then you need to add that
>> before it is a complete, realistic model.
>
> It does, of course.  But only to build the first propulsion laser, not
> to sell power for a dollar a kWh.  Now if you have a *market* for 5 GW
> of power at a dollar a kWh, we are in business.

Hmm, let's see.  You know of any customers who
1) are operating in a mostly-sunny environment,
2) have a high cost of importing fuel to their bases,
3) have a need for mobility (like, say, being able to
repoint their incoming power),
4) already have a no-fly zone above the places they
would like to get power, and
5) have a history of "price is no object" mentalities?

Granted, their current need won't last forever.  But
if they can pay to get the sat up there, and they
take most of the power - you only need to tap it for
a few minutes (maybe up to half an hour) to do the
launch, and these intervals can be scheduled for
moments of anticipated low demand - then, well...

>>> Perhaps.  I freely admit the model may have errors in assumptions or
>>> formula.  Though saying that without looking at the model seems a bit
>>> over the top.
>>
>> No, it's basic business theory.  If you can make a profit with
>> practice X after it's developed, and a lesser profit with
>> practice Y that does not take significant development, then
>> you can compare the efficiency of developing X and then
>> making more money over time versus just using Y.
>
> I f can figure out a way to get this started on a smaller scale,
> please do.  If you can, I will support your efforts.  I am not welded
> to this approach.

What is the gating factor on cost per kg, that makes a
10 ton solar satellite that much more efficient than a 1
ton, or a 0.1 ton?

(Side note: "a 0.1"?  "an 0.1"?  Spike, maybe you could
clue me in as to which is correct?)

> As an analogy, it is not possible to mine a low grade ore body and
> make money if you try to do it on a small scale.  Sunlight is a low
> grade (dilute) energy source.  Collecting it on a scale of tens of TW
> is a big task no matter how you slice it.

If tracking mirrors are that much cheaper and lighter,
then how about replacing most of the PV cells with
those?

>>> I am mainly interested in making a case that there *is* a way out of
>>> the energy/carbon problems without an 80% die off.
>>
>> The theoretical case has long been made.  The challenge now
>> is the litmus test: actually doing it.
>
> That's news to me.  Where?

The theoretical case having been made?  Here, for one.
This very list.

Most of the general public does not seriously believe
that humanity will have an 80% or worse die off in the
next century, but they do believe that the energy/carbon
problems will get, if not solved, at least not very much
worse than they already are - which generally requires
at least a partial solution.

>>> The cost of power at current $10,000/kg is dominated by the lift cost
>>> of ~50,000/kW.  Cost of power at that transport rate is ~$2/kWh.
>>>
>>> For zero lift cost, the cost would be around 1.4 cents per kWh.  The
>>> derivation of this is in the paper.
>>
>> It sounds like you have bigger concerns than the lift cost, if
>> that is not a majority of the cost.
>
> It's around a third of the total cost.  I really don't understand your
> objection to the other costs.  Do you know of a less expensive way to
> make and transmit power to the Earth?

Strawman.  My objections regarding the other costs have
to do with the other costs themselves, not the benefits.
To wit: what *are* the other costs, and how big of a factor
are they?

> From: Dan <dan_ust at yahoo.com>
>> Or even no payback. It could just be a proof of concept that doesn't even break even, but merely shows it can be done at such and such a price and gives good clues to what it would be like to operate the thing and what might happen at larger scales. Also, in this case, you're not blowing all your resources on a gigantic project that might fail, but a very small one where a failure is far less costly and you can more easily recover from it to try again.
>
> That's a great idea!  Wonder why it has not already been done?
>
> If you can follow the physics, why not is in here:
> http://www.sspi.gatech.edu/aiaa-2009-0462_ssp_alternatives_potter.pdf
>
> There are scaling problems that are due to the transmission of
> microwaves through the atmosphere and the distance to GEO.
>
> It is about the same expense to built one demonstration power
> satellite with conventional rockets as it is to set up the
> transportation pipeline and build them by the hundreds.

The paper was written by Boeing.  Boeing institutionally
does not believe in cheap solutions: they threaten
Boeing's business model.  They have a history of making
assumptions to justify keeping things expensive.

A demonstration - pure demonstrator - satellite can be built
and launched for tens of thousands - not millions - of dollars.
It's called a CubeSat.

Yes, it would provide tiny - infinitesimal - power to the ground.
Yes, it would not be cost-efficient to do just 1U CubeSats.

But as a pure demonstrator?  There is a world of difference
between "trivial" and "nothing".

Besides, if lasers really are that much better, and provide
you energy for every launch thereafter, could you bootstrap:
launch something small, then use it to power launching
something a bit bigger, then gang them up to power
launching something yet bigger, and so on exponentially?

How much mass could you launch at once with, say, a
single kW?  How many such launches would you need to
make your next kW?