[ExI] Written for another list

[Adrian Tymes]

On Sun, Aug 5, 2012 at 9:26 AM, Keith Henson <hkeithhenson at gmail.com> wrote:
> On Sun, Aug 5, 2012 at 5:00 AM,  Adrian Tymes <atymes at gmail.com> wrote:
>> On Sat, Aug 4, 2012 at 10:30 AM, Keith Henson <hkeithhenson at gmail.com> wrote:
>>> You asked how I calculated what the first power sat was worth powering
>>> propulsion lasers vs selling the power.
>>
>> Yes.  And as noted, I see that you calculated this
>> using false assumptions.
>
> OK.  Compared to selling the power on earth, what is the same power
> used for propulsion lasers worth?

By itself?  $0.

It only becomes worth something when paired with the
launch vehicle & service, at which point the worth of the
power becomes inextricable from the overall worth of the
launch - save as a cost line item.

The cost line item can be $0 (since you already own all
the infrastructure and you're not paying anyone else to
use it), or at most, the opportunity cost of not selling it
as electricity (exactly equal to the market cost of
electricity, by definition).

>> Use less diodes per m^2,
>
> That might be possible, using an expensive horn antenna with one diode
> down deep in the horn.  It's been close to 50 years since I had a
> microwave antenna theory class so I am not sure.

Why would it need to be expensive?

>> or assume more ohms.
>
> Now, that you can't do.  The impedance of an antenna is fixed by physics.

Of any given antenna, yes, but you can change the antenna.
The impedance is best matched to the impedance of the line
carrying signal to/from the antenna.  V = IR, we have a minimum
V, and R is a function of materials.  So use better conductors =
less R = more I for the line, and then configure the antenna to
match the line's I.

Materials science might not quite be advancing at Moore's Law's
pace, but it is getting better.

For instance - and standing outside the general thrust of "how
do we do this at first" - what about tapping part of the power
for cryogenics, enough to make the antenna from
"high-temperature" (but still sub-room-temperature)
superconductors?  What would 0 resistance enable?

>> Or just use
>> less m^2: at 1 m^2, that's 1/4 kW, which is less than MW.
>> Even 1,000 m^2 is only 250 kW.  But less diodes per m^2 is
>> probably the easiest solution, if you're designing for low power.
>
> That means focusing the microwave beam into a tighter spot.  Which
> means a larger transmitting antenna in space.

Or visible light, or different focusing mechanisms.

>> So again: use visible wavelengths.  Or perhaps masers,
>> to reduce divergence.
>
> Visible gets interrupted by clouds so it has the same storage problem
> as solar PV.

We're talking bootstrap phase, before you have the budget
for a large sat.  Interruption by clouds is acceptable for this
phase.

> How does a maser reduce divergence over a phased array?

Smaller beam waist = smaller footprint.

>> Are you just trying to make a theoretical case, or is this
>> something you want to actually make happen?  There is
>> a big difference between the two.
>
> True.  Let's be generous and say I have put in $150,000 of time on
> this over the past 7 years (with a year off for jail and related court
> stuff).  If the project takes 150 B, that's a factor of a million
> higher.

That didn't answer my question.  Are you just trying to make
a theoretical case, or is this something you want to actually
make happen?  People can and do spend huge amounts of
time into just making theoretical cases, so that you have put
much time into it could support either answer.

If you're just making the case, do you just want to argue that
it is physically and technically possible given an infinite budget,
or do you want to make the case that it is economically
feasible too?  In the latter case, you can not ignore startup
costs and making a plan for how to bootstrap up to having
multi-GW microwave powersats.  Yes, it's fine to have that as
a goal, but to make the case, you have to show how we can
get there, and "assume a huge investment before the specific
organization putting the sats up has shown it can put lesser
powersats up with a lesser budget" is as much of a nonstarter
as "assume gravity stops for an hour".

> The point, in case you missed it is that I don't need to put up a
> cubesat to make the case that microwaves can be generated in space and
> sent to the earth.

That's not the point.

The point is to show that *you*, or whichever organization is
doing this, can assemble, install, and operate the infrastructure.
This is required before said organization can acquire a large
investment.

For the kind of investment an organization can get before that
step...well, it can put a cubesat into LEO, and a cheap antenna
that the sat only hits when over the horizon (and perhaps using
visible light, so it's further limited to when it's not cloudy).

> As for economics, showing how to get the cost down is the main point
> of the work I have done.
>
> You really don't need to be nasty.

I do if it's the only way to get across that, despite your claim
that you're doing this for the economics, you're being
aggressively naive about economic basics.

>> You start with
>> small scale technical demonstrators, then work
>> your way up.
>
> There will be such done on the way to power sats, but they just don't
> scale so to make money on the project you have to finish a very large
> minimum set of infrastructure.

You don't have to make money at first.  At first you just have
to demonstrate that you are capable of doing what you say
you want to do.  That is how you attract investment to get
that minimum infrastructure to be profitable.