Originally Posted by
balsa model
So it does look like the solution works great. (And an impressive engineering team, knocking down problems one-at-a-time.)
But what is the problem again?
And I'm not trying to disparage this effort - only the marketing explanations look to me naive or dishonest.
To be more precise, this claim of better lift to orbit:
Carrying quite a bit of extra hardware so that you can fly obliquely through the atmosphere to save a small fraction of the oxidizer weight, then claiming that overcoming the thick atmosphere in this manner is an achievement, just does not quite add up.
As to London-to-Sydney: what will be the idea for redundancy here? One glitch in this pre-cooler and I imagine the consequences will be spectacular.
Again, not in the spirit of disparaging the actual science/engineering of this thing.
There's a big opportunity for something like this in in-space assembly plans. To build a big satellite on the ground is very expensive - big facilities, big transport problems, big assembly hall for the launcher stack, big test faciliites, etc. Whereas if you can launch, say, 1 ton lumps and reliably join them up in orbit, you save all that cost on the ground. And there's no real limit on how big the final spacecraft is.
The advantage of SKYLON is that it can potentially launch a lot of 1 ton lumps in the time it takes a rocket launcher company to perform a single launch cycle. It could also bring them back again which, weirdly, makes things on the ground cheaper too; a module that's dead on arrival in orbit can be brought back and fixed, so that means one might be more willing to take a chance on less design analysis, testing, etc.
Wild guess here - it'll probably take roughly Concorde levels of maintenance to keep it flying.
The "flying" bit is good because it's a more efficient way to gain height than a purely ballistic ascent. The Saturn V burnt a whole heap of fuel just in the first couple of thousand feet, not really gaining any orbital velocity at all.
A pre-cooler packing it in does sound like a major event in flight. It might depend on thrust asymetry, but if it happened at a high enough height it might still make orbit on the other engine. What matters is getting that velocity up, and taking a little long doing might mean you get to a lower orbit. For example, the Shuttle sacrificed a little altitude for speed in its flight profile as a matter of course.