[AR] Skylon and related (was Re: SSTO)
- From: Keith Henson <hkeithhenson@xxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Wed, 14 Feb 2018 13:06:57 -0800
Tue, 13 Feb 2018 Henry Spencer <hspencer@xxxxxxxxxxxxx> wrote:
On Tue, 13 Feb 2018, Keith Henson wrote:
Snip
...needs about $100/kg to LEO. I don't think rockets can reach that
number...
If Skylon can, almost certainly rockets can do even better. A reusable
TSTO burning LOX and some cheap hydrocarbon should be rather easier to
develop, and there's no reason operations couldn't be scaled up to the
same launch tempo.
Remember I am thinking in terms of power satellites and the need for
upwards of half a million flights a year. In such a context,
development cost is spread over so many vehicles and launches as to be
negligible. If the rocket replacement for Skylon got 75 tons per
flight to orbit, we would still need around 100,000 flights per year.
In order to get down into the $100/kg to LEO range, the vehicles need
to fly around 1500 times, with two rebuilds (reskins) at 500 and 1000
flights. Can we do something similar with rockets?
On the positive side for both rockets and Skylon, the fight is to
equatorial LEO, perhaps 300 km.
The LOX costs almost nothing compared to the fuel, and "There's nothing
magic about rubber wheels rolling on a runway that's gonna make it cheap
to operate." (Mitch Burnside Clapp).
Compared to rockets, aircraft are cheap to operate. In theory, Skylon
has safe abort modes through the entire launch, though an abort just
before rotation is a dicey stopping problem. It's not highly stressed
because it flies up the constant dynamic pressure line.
Rockets or Skylon, I don't really care as long as they can get the
cost to where it is required for power satellites to undercut fossil
fuels. If something can't, then power satellites just don't make
economic sense.
Keith
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