[AR] Re: 500,000 tons per year to GEO (off topic)

  • From: Keith Henson <hkeithhenson@xxxxxxxxx>
  • To: arocket@xxxxxxxxxxxxx
  • Date: Fri, 4 Apr 2014 08:01:48 -0800

On Thu, Apr 3, 2014 at 9:09 PM, Peter Fairbrother <zenadsl6186@xxxxxxxxx> wrote:

snip

> More, even if Skylon-plus-lasers just works somehow (and is somehow
> politically acceptable, big laser weapons being involved), that isn't even
> close to the cheapest or fastest way to get 500,000 tons per year to orbit.

Please go into details.  I am not welded to Skylon and lasers.  I am
well aware of the problems involved.  If you have better ideas, I will
gladly adopt them.

snip

> If we are going to launch that much mass to GEO (and need only one miracle,
> space power) then the best and cheapest and lowest-risk way is to use two
> stages.

Ah, it already is two stages.  Laser augmented Skylon to LEO and a
laser powered, 30 ton second stage from LEO out to GEO.

> A single stage SSTO is sexy, but hellaciously expensive and terrifically
> wasteful. A SSTO with lasers? Those expensive Sabre engines just sitting
> there doing nothing while the shell goes to GEO and back? Too high-tech and
> therefore too expensive, too low performance, too low flight rate, far too
> much technical risk.

The Skylons never go above LEO.  They reenter after one or two orbits
and fly every other day.

snip

> If we can assemble the powersat in bits which can each provide enough solar
> power to drive an electric drive of some kind we can limit the fuel needed
> to get to GEO - and no lasers required.

This was Boeings approach clear back in the 1970s.  They were going to
assemble in LEO and fly the powersats out to GEO under their own
power.  Took about 6 months.

Then someone ran the calculation.  Even in those days, there was
enough space junk that the odds were massively against one of them
making it to GEO without being wrecked by space junk.

> Plus, nothing much has to come back from GEO. Especially not a jillion
> Skylons.

The current plan has 72 second stages arriving at GEO every day.  They
are scrapped at GEO and the material used for power satellite
construction.  At this production rate, they are not going to be
expensive.

It was the only way I could get the flow rate of materials up and the
cost down to where the overall project made sense.

But if anyone has better ideas, I would be delighted.

Keith

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