[ExI] Written for another list

[Adrian Tymes]

On Thu, Aug 2, 2012 at 8:29 AM, Keith Henson <hkeithhenson at gmail.com> wrote:
> On Thu, Aug 2, 2012 at 4:51 AM,  Adrian Tymes <atymes at gmail.com> wrote:
>
>> On Tue, Jul 31, 2012 at 9:52 PM, Keith Henson <hkeithhenson at gmail.com> wrote:
>>> In the bootstrap plan I have outlined, the power from the first
>>> expensive (built with conventional rockets) power sat is used to power
>>> propulsion lasers.  That lets you build more power sats at a much
>>> lower cost than the first one.  The energy the first one generates is
>>> worth around 100 times as much bringing up parts for more power
>>> satellites as it would be to sell it to ground markets.
>>
>> How do you calculate this 100 times?
>
> The power can be used to raise 500,000 tons per year to GEO.  At
> $100/kg this is worth $50 B per year.  3.5 GW sold for power at 2 cent
> per kWh brings in $0.56 B/year

False comparison: you're leaving out all the non-energy
costs of launching stuff - and the vast bulk of modern
launch costs is non-energy.  Instead, it is the
bureaucratese and project management that comes
with a series of one-off prototypes, one after another.

So, no, you would not be getting $100/kg out of it.
(Even if you were, you're "paying" yourself: always a
red flag that you're getting an incorrect value, and not
an income stream you can use to fund the rest of the
project with in any case.)

>>> There has been a lot of looking at selling power from space to the
>>> military.  Never reached the big study phase because there are just
>>> too many problems.  The military wants power in MW or sub MW chunks.
>>> Microwave power sats at 2.45 GHz don't scale below 5 GW
>>
>> So what happens if you put a 50 MW sat up?  Is it:
>>
>> 1) More expensive per MW?
>> 2) More expensive overall - not per MW, but the total project cost -
>> than 5 GW?
>> 3) Impossible?
>>
>> If it's just #1 - so long as the total cost is lower, that's fine.
>>
>> #2 or #3 would need serious justification.
>
> Between 2 and 3.

Your proof does not convince of that.

> You need a minimum induced voltage on the rectenna
> diodes for them to forward conduct.

Watts are not a measure of voltage.  Volts are voltage.
The minimum voltage can be induced for a power less
than MW, possibly sub-W.

For example, the common household microwave oven
can induce voltage in rectennas places within them.
They use much less than a MW to do so, and the
rectennas are less than a meter across.  (The results
tend to destroy the oven, so casually experimenting
with this is not advised, but there is ample evidence
that power transfer on this small magnitude works.)
Granted, the distances are far, far less than orbital,
but we're just talking about the minimum power
received to drive the rectenna.

> 50 MW is 1/100 of 5000 MW.  So
> the ground antenna would need to be one km across and the antenna in
> space 10 km in diameter and would cost 100 times as much as a
> transmitter for a 5 GW unit.

How does the fact that you're transmitting less power
translate into requiring a larger antenna?  Unless
you're basing off the minimum - in which case, you
need to show why the minimum is so gigantic.

>>> But if we were to build laser power sats for the military, they would
>>> probable use them as weapons rather than power.
>>
>> Lasers like that are strategic weapons.  They hit areas, not
>> individual targets.
>
> Not at all.  To be useful for propulsion, they need to put about all
> that power into 150 square meters at 20 MW/m^2.  That's a little over
> 12 meters across.

That's "strategic" in modern military parlance.  You're
hitting an entire building, not a person or vehicle.
This is trivially defeated by colocating the target with
civilian infrastructure, which infrastructure is an
unacceptable target (to most modern Western
militaries, anyway).

Besides, they already have ample and sufficient
weapons to take out targets of that size - and more
controllable, too.  A missile can be pulled off if it is
realized after the shot that the target is incorrect.
A laser - once you pull the trigger, that's it.

>> What about using shorter wavelengths, such as visible light?
>
> Then a cloud cuts off the power.  It's part of the reason we start the
> laser propulsion above 10 km, to get over the clouds.

I'm talking about for prototypes and bootstrapping,
where intermittent interruption by clouds is acceptable.
You're not going to have need or even much use for
launch power 24/7 until way down the line, when you
have enough capital that you're manufacturing sats
like crazy.  (Remember, the satellites themselves
cost a lot of money, beyond their launch costs.
Unless you have them manufactured on the Moon -
and let's assume fully automated manufacture so we
can handwave ongoing labor costs - but then, the
tough part becomes getting the infrastructure up there
first.)

>>>>>>> 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.
>>>
>>> I don't remember such discussion.
>>
>> And how long have you been on this list?
>
> Off an on since 1989.

You must have been off every time the case was made,
then.

>> Ways to save the world without a massive dieoff are
>> discussed not infrequently.  Maybe not any specific
>> proposal or case, but the general discussion has
>> long since chased away any presumption that we
>> must necessarily fail and that humanity is doomed.
>
> Well, this is one specific proposal.  There is no certainty that I got
> either the assumptions or the spreadsheet formulas right though.

Yes, but you said you wanted to make the case that
there is at least one way.  That case has already been
made in general.  What you're actually talking about
is your specific proposal, so you need to be clearer
about your intent.

You need to be clearer to yourself, first and foremost,
as to why you're doing this.  That will help you make
your case better.

>> I meant that I didn't understand *that* the rest of the cost was
>> generation equipment.
>
> OK.  The rough cost breakdown is in the paper.

That's the one you haven't sent?  Or did you mean the
Boeing one, which I reject as an unreliable data source
since they have a history of invalid (and often
cost-inflated) data for this sort of thing.

>>> You could pack a few mW of microwave transmitter into a CubSat.
>>>
>>> Why bother when there are communication satellites pouring down as
>>> much as ten kW of microwaves?
>>
>> Because you don't have the money to put up a big enough
>> satellite to pour down 10 kW, but you might have enough for
>> a CubeSat.  And because there are concerns other than
>> just "can it be done in theory" that you must demonstrate.
>
> The communication satellites are already up there pouring down kWs of
> power.  Why do I need to put up a mW cube sat when they are already
> doing the same thing at orders of magnitude more power?

Because there are concerns other than
just "can it be done in theory" that you must demonstrate.
The biggest one: can *YOU* do it?  Can you, personally, get
all the pieces together, make it fly, get some - any - amount
of power, and thus show that you have indeed solved all the
challenges?  (All the analysis in the world might miss some
physics objections; actually doing it will automatically do
it.)

Put another way: why do you believe that the fact that
other people have put up comsats pouring down KW
of power for communication, will convince anyone that
you, personally, have the know-how and ability (if funded)
to put up satellites that would pour down any amount of
power for a different use (power itself)?

> The hard part is not the power satellite design or getting the power
> down.  That's been understood for decades, Boeing had a $10 M plus
> contract to do so back in the late 70s plus they spent a *lot* of
> their own money on it and still have enough interest to send people to
> conferences.

Perhaps it wouldn't be hard for Boeing.  But we're not
talking about Boeing.  We're talking about you.

> The hard part is getting the cost of lifting hundreds of thousands of
> tons of parts to GEO down to where power sats make economic sense.
> Laser propulsion is the way to go.  That's only recently become
> possible with large versions of the tiny laser diodes in CD player.

Right.  So, how are you going to show people that you
can do this?

> No sane investor is going to put me in charge of spending the national
> budget of a fair sized country for ten years.  And putting up a
> CubeSat would not affect that fact one iota.

By itself, perhaps not.  But putting up a CubeSat would
justify putting you in charge of something larger.  And
if that works, larger still.

And that's *how* people eventually wind up in charge
of budgets like that: they worked their way up.

> This is about a
> *concept* for how to get the cost to GEO down.  I don't even have an
> IP interest in it because (for various reasons) I have been doing this
> work open source.  The idea, meme if you want, stands or falls without
> me.

Then your work is in vain.  If there's no chance that
anyone will ever bend metal to your design, be inspired
by it, or any other concrete result, you may as well have
done nothing.

I speak from experience.  I have multiple patents for
various systems, and I now and then try to get others
to build them - see what it would take.  If I just made
the design and left it there, not seeking to get it to
those who could make it real, it would have been a
wasted effort.  (As it happens, I have yet to get some
of the designs to said people, so those efforts have
yet to bear fruit.  Others have born fruit, and it was
excellent.  But that never would have happened had I
paid no attention to the intermediate phases of how
to make the ideas real.)

>> If a single CubeSat can get a few mW down to the ground,
>> what kind of thrust could you get on a 1-mg launch vehicle?
>
> It's easy enough to calculate.
>
> One mw is one mJ/s.  100% applied to one mg it would generate
> acceleration at one meter/sec, which is about 10% of what you need
> just to overcome gravity.

So you could launch a 1 mg vehicle with about 50 mW, then,
assuming 20% efficiency?

> But a CubeSat would be hard pressed to put out a mW.

CubeSats - if dedicated mostly to solar panels and
transmitter - can pull in and put out a few Ws.  For
example:
http://www.clyde-space.com/cubesat_shop/solar_panels/1u_solar_panels/50_1u-cubesat-side-solar-panel

> And that mW
> could not be focused by something that small so the energy would go
> more or less uniformly over the entire space.

Orbit-to-ground laser communicators are being
investigated for CubeSats.  Last I heard, 1 W of
power at the source results in some number of
mW power of signal received.  One could simply
not bother to encode a signal, and instead use it
for power directly.  I forget whether they're using
visual, microwave, or another frequency, but the
receivers are less than a meter across.