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
_______________________________________________ ERPS-list mailing list [EMAIL PROTECTED] http://lists.erps.org/mailman/listinfo/erps-list
