[ExI] Power sats and payload size was Small solar satellites

[Keith Henson]

On Sat, Feb 25, 2012 at 5:12 PM,  Adrian Tymes <atymes at gmail.com> wrote:

> On Sat, Feb 25, 2012 at 2:28 PM, Keith Henson <hkeithhenson at gmail.com> wrote:
>> If you make the target 100 GW/year, which is small compared to the
>> need but still significant, then the mass in GEO you need (at 5 kg/kW)
>> is 500,000 tons.
>
> Ah.  So the ~1 kg sats would, at best, work as a demonstration so you
> could get the investment needed to do a multi-ton launch.  Thanks.

Hmm.  Not sure you grok the sheer scale involved.

>>> * How many satellites would you need to get any measurable output
>>> at ground side? ?Not enough to export useful energy, but enough to
>>> demonstrate "ground truth" that the system works.
>>
>> You are doing that right now if you have a Dish network TV. ?Ever set
>> one up? ?The energy is certainly measurable.
>
> Dish network satellites are multi-ton.  I was wondering how many 1 kg
> satellites would be needed to, collectively, produce measurable output
> on the ground.

One would do it.  I don't think you appreciate just how little power
is needed to be "measurable."

>>> * What would the initial investment to cover manufacture, assembly,
>>> and installation of those components (and anything else necessary
>>> for a minimum ground truth version)?
>>
>> The power satellites and the ground station are not the hard parts.
>> It's the transport system that makes or breaks power satellites. ?That
>> takes ~250 Falcon Heavy launches to set up plus the cost of the laser
>> hardware, power plant and heat sink (a square km). ?The launch cost
>> alone is $25 B, but for that number of launches SpaceX might give a
>> substantial discount.
>
> Yes.  Thus, again, why I proposed demonstrating it with a cheaper
> launch system, to help attract the investment to cover the larger launch
> cost.

I don't exactly know what you mean in this context by "cheaper."  Just
about any existing launch rocket is "cheaper" for a one off launch
than designing, building and testing a new one.

> And yes, it would offer a substantial discount.  The majority of launch
> costs arise because the equipment involved is used so infrequently.
> If you had ~250 launches, at 1/month or more frequently, you could
> slash launch costs by over half, possibly to 10% or less.

One per month would take 21 years.  Starvation will get here first.
One every other day would take 16 months.

The remaining 15,000 tons would go up as a bootstrap.  That is 3000 5
ton flights.  At 30 flights per day (3 per hour x 10 hours per day) it
would take 100 days to bring up the rest of the parts for 2 GW.  Fly
them every other day and you need 60 1/4 scale vehicles.  No spares,
none "in the shop."  If you crash a few, the project just stretches a
few days.

At the end of that time, you have enough power for full scale
vehicles.  At 72 launches per day, and flying every other day, you
need ~175 with spares and some in the shop.  Each vehicle will fly
~183 times a year.  If they wear out in 500 flights, they will last
~2.7 years.  5.5 per month will need to come off the production lines
to replace those wearing out.

I am just running through a pert chart,  This might not be the best or
lowest cost way to get the laser seed or the first full scale (2 GW)
laser built.  If anyone has better ideas, I am open to them.

Keith