Yes, but get back to me when you come up with an SSTO, and particularly
an airbreather, for which that is the case.
On 2019-03-16 21:15, David Summers wrote:
Just to check my understanding of what you are saying, that follows
only if the payload mass to empty stage mass fraction is small, right?
So if you had an SSTO that arrived on orbit as 50% payload then the
performance difference would be much smaller.
Of course, as Bill showed a while back you could also use that same
technology base to make an even better two stage to orbit vehicle. But
eventually, when we have "sufficiently advanced" technology
(indistinguishable from magic), an SSTO will the better architecture.
We could save fuel or increase payload using drop tanks on 747s, for
example, but we don't.
(I could see an alternate history where we did, though. Halfway to
China, drop the tanks into the Pacific for someone to fish out and
bring back for reuse!)
Thanks!
-David Summers
On Sat, Mar 16, 2019 at 6:30 PM Rand Simberg <simberg@xxxxxxxxxxxxxxx>
wrote:
And as with any SSTO, Skylon would suck for off-nominal (higher
inclination/altitude) missions.
On 2019-03-16 16:24, Evan Daniel wrote:
The original presentation for the SpaceX BFR called for $500/kg tothe
Mars surface, including LEO refueling, with the capital cost of
transit ship being a very large fraction of that. They didn'tbreak
out the numbers in detail to give a LEO payload cost estimate, butI
infer it was much lower than $500/kg.see
Numbers since have gone up, and sizes and flight rates down, but I
think if you asked SpaceX to project out to those volumes you'd
numbers below $100/kg to LEO. I don't think Skylon is unique inthat
fashion.projections.
One can, of course, believe or not believe either set of
But, I think it's (at least) as reasonable to suppose that SpaceXthat
could hit that target with a BFR style architecture as to believe
Skylon can hit its target.<hspencer@xxxxxxxxxxxxx>
Evan Daniel
On Sat, Mar 16, 2019 at 6:23 PM Henry Spencer
wrote:orbit low
On Fri, 15 Mar 2019, Keith Henson wrote:
Reaction Engines is the only company that projects a cost to
get theenough for power satellites to make sense. They think they can
to acost down to a hundred dollars a kg to LEO...
The cynical observer would say that they are the only ones whose
projected
startup costs are so colossal that they *must* project far ahead,
Less-challengingvery high flight volume, to make their case close.
assumptions...approaches should do better, not worse, given the same
projectbut
they don't need such rosy assumptions, so they generally don't
theso
far beyond the current market.
(Max Hunter used to suggest that cost plots should always show
it.)marginal cost of a single added flight, as a way to hint at bulk
prices
without having to justify massive market expansion, but few do
Henry