What I never understand when reading about Skylon, is why the project try to do single stage to orbit directly? A reusable first stage would in itself be valuable and neither cost so much to develop, nor be risky by walking the edge of weight gain etc. ssto could be version 2.
(I'm not that knowledgeable on the subject, flame me if your day has been bad, just add information. :-) )
Edit: Symmetry, SpaceX is itself trying for reusable stages. As far as I can tell, it should be the sweet spot?
Single Stage to Orbit (or any type of reusable launch system) invariably adds complexity and weight, which in turn eats up any gains by being able to reuse stages. It just isn't worth it to add complexity unless you go whole hog and make the entire thing SSO.
(I'm not that knowledgeable on the subject, flame me if your day has been bad, just add information. :-) )
Edit: Symmetry, SpaceX is itself trying for reusable stages. As far as I can tell, it should be the sweet spot?