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

[Adrian Tymes]

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.

>> * 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.

>> * 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.

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.