On Fri, 12 Mar 2004, Ian Woollard wrote:
> However, compared to a similar construction TSTO I found my payload
> dropped precipitously, by 75%.
> That's *really* bad.
No; why should it be? They're different classes of vehicles.
The original Kistler scheme, with the LAP, is *not* a TSTO -- it's an
assisted SSTO.
And as Max Hunter said, the bad thing about assists is that as soon as you
start planning for them as part of the baseline, people start mumbling
about optimized staging, and the idea of building an almost-SSTO -- in
hopes of getting to a real SSTO in the second generation -- quietly dies.
As it did at Kistler.
> So I have to either build my launch vehicle 4x bigger or launch 4x more
> often. IMO neither seems like a brilliant idea.
On the contrary, both deserve serious consideration, and either might well
be the way to go.
It's abundantly clear that if you are trying to minimize gross liftoff
mass for a given payload, you will end up with about three stages, with
the split carefully optimized. But gross liftoff mass is a really stupid
figure of merit, unless you've got outside constraints like "must fit in a
submarine crosswise" or "must be carried aloft by a 747". Almost all that
mass is fuel, which costs almost nothing.
And spending more to develop a more complex vehicle that will fly less
often is *not* a smart economic move.
Henry Spencer
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