[ExI] SpaceX Super Heavy and Space Solar

[Adrian Tymes]

On Mon, Oct 21, 2024 at 4:47 AM efc--- via extropy-chat <
extropy-chat at lists.extropy.org> wrote:

> On Sun, 20 Oct 2024, Adrian Tymes via extropy-chat wrote:
> > On Sun, Oct 20, 2024 at 5:00 PM Keith Henson via extropy-chat <
> extropy-chat at lists.extropy.org> wrote:
> >       On Sun, Oct 20, 2024 at 1:28 PM Kelly Anderson via extropy-chat
> >       <extropy-chat at lists.extropy.org> wrote:
> >       >
> >       > Has anyone run the numbers on whether space based solar makes
> sense yet if the Super Heavy keeps some of its economic
> >       promises?
> >
> >       Yes.
> >
> >       100 tons is 100,000 kg. If a flight gets down to even $10 million,
> >       that's $100/kg to LEO, double that to GEO with electric propulsion.
> >       6.5 kg/kW is a reasonable number, so $1300/kW for transport,
> $900/kW
> >       for parts and labor, plus $200/kW for the rectenna.  That adds up
> to
> >       $2400/kW.  Divide by 80,000 to get 3 cents per kWh.
> >
> >       Looks good from energy return time, takes about 66 days to pay back
> >       the fuel energy used to lift it to orbit.
> >
> >       The problem is that it takes 500 flights to build one.  A
> reasonable
> >       construction rate of 50 a year would take 20 years to replace
> 1/3rd of
> >       current consumption. I don't know if the atmospheric damage of
> 25,000
> >       flights per year would be acceptable, but NOAA could answer that
> >       question if asked.
> >
> >       The money through this program is $600 B/year.
> >
> >
> > Needing that much money up front, before the program is generating
> revenue, makes it economically infeasible.  No one with the
> > requisite finances will believe that heavily in the revenue until after
> a small scale prototype is demonstrating, even at
> > significantly lower economic efficiency ($0.10-0.50 per kWh, perhaps).
> >
> > You may see such a prototype as "wasteful" or "wasted", and in the long
> run it would become obsolete.  It is a necessary expendable,
> > in a sense, to get the program started.
> >
> > In that light, what are the numbers for a prototype that could be built
> with just one Super Heavy?  The $/kWh will be worse, but you
> > have an absolute maximum to LEO of 100 tons.
>
> Yes! Why couldn't it be built in modules, expanding as you go?
>

 Note for context: I am working on a rocket system that - if everything
goes absolutely, unreasonably right - might result in 100-200 tons to LEO
service in a decade, with $100/kg or less.  While that point is way too far
out to guarantee service yet, I am at least academically interested in what
happens to these numbers if the cost drops to, say, $80/kg, or $50/kg.
Lower $/kg becomes easier to justify the higher the annual flight rate gets
- but requires a larger, less feasible amount of funding, especially if it
comes from a single project like this.  (One could imagine competing
constellations, both using the same launch provider, to get up to a net
total of 1/3rd of humanity's power consumption in only 20 years, but this
is highly unlikely without a far lower cost option for someone to go first.)

So, at what $/kg does at least a prototype solar power satellite
constellation become remotely fundable?  And how small could such a
prototype be to make sense for a specialized use case that could justify a
higher $/kWh?
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