Re: Re: Book, Single Stage to Orbit

At 08:32 PM 3/12/2004 +0000, Ian wrote:
>Henry Spencer wrote:
>
> >The original Kistler scheme, with the LAP, is *not* a TSTO -- it's an
> >assisted SSTO.
>
>I don't really see that. As soon as you have that staging event, it's 
>clearly not SSTO. Or if you look at it as a near SSTO, SSTOs are 
>relatively heavy, and the assist has to lift that lot up to a decent 
>fraction of 100km. I think this vertical lift scheme is actually the worst 
>of all possible worlds.

I would still call an assisted SSTO a TSTO, but I disagree quite strongly 
with your verdict -- I think a vertical lift booster is the BEST near term 
scheme for coming at things from a low cost perspective.

If you are set on launching commercial satellites, then it probably doesn't 
pan out, because a large, fixed payload requirement would require a very 
large vehicle.  However, if you can accept a smaller payload and make up 
for it with higher flight rates, there are sound developmental reasons why 
you would want to go this way.

A LAP is less complicated than a flyback booster.  In fact, a LAP would be 
almost exactly the same complexity as our X-Prize vehicle, and it could 
even be operated with the same propellant.  If you need to make two 
vehicles, it is better to make one complex / optimized vehicle and one 
simple vehicle instead of two complex / optimized vehicles.

Development and testing is much easier with a strictly vertical booster 
vehicle with no downrange requirement, and the simple LAP can have its own 
revenue stream for suborbital uses.  This can hopefully bootstrap the 
development of the orbital stage.

I think it has been shown reasonably well that the market isn't going to 
provide the money to build any large RLV.  Certainly not to us.  So, we 
need to find the cheapest way to do something useful.  I think that an RLV 
should be sized to hold a single person in a space suit, or the equivelant 
amount of cargo, which covers RASCAL class payloads.

To a first approximation, payload fraction does not matter.  A true RLV 
with high operability can throw away 90% of the payload that an optimal 
design could have, and still be a huge advance over existing options due to 
reliability and fly-on-demand.  Once there are competing RLV's, then it 
will be an issue, but until then all that really matters is getting one flying.

John Carmack