getting back on the European track as our Fearless Leader reminds us, would the small orbiter of more developed European sapce effort be a delta-winged vehicle like Von Braun's concepts or might it be an early high-speed lifting body concept? I know that lifting bodies were being studied by the mid-1960's. Would it, perhaps, draw on teh developmental experience from Concorde? Lots of possibilities here (imagine a Concorde prototype used as a supersonic drop-test launch vehicle) that could make for very interesting concepts.
In my mind's eye, the European spaceplane is more Von Braun-like, because it's actually more similar, aerodynamically speaking, to a 1960s Skylon, in that it carries a large amount of empty tankage into orbit in order to reduce it's density on re-entry, which in turn leads to a more benign heating curve than the NASA shuttle. That means it's shape doesn't have to be driven by re-entry considerations so much, which was a major factor behind the lifting body studies.
Here's a thought: could you design a liquid fuel rocket motor that used two different fuels with the same oxidiser? The reason I ask is that putting kerosene in the spaceplane's wing would offset some of it's drag/weight/cost penalty at lift off, but I doubt that the volume would be enough for the whole third-stage fuel requirement. You could go for all-kerosene with more fuel in the fuselage, but kerosene isn't the most
efficient rocket fuel, just one of the more
convenient ones (no pressurisation or cooling required and not outrageously horrible to handle), so I was wondering if you could have, say, liquid hydrogen in the fuselage and kerosene in the wings and mix both in the combustion chamber with the oxidiser of your choice.
In my concept Concorde never happened, which is one of the sources of cash for the ESA programme. It's been said that Concorde was "Europe's moonshot": in my world, we actually had that moonshot (eventually) instead.
Logically, I suppose you could argue that a Mirage IV airframe would be a better spaceplane analogue than a Mirage III for training purposes, but I originally came up with the idea because I've bought a Falcon 3 x 3-seaters conversion in which the Mirage IIIF bits were surplus to requirements.