Good images. That first concept of the space shuttle looks workable. It'd be better if it was a single stage, if only to avoid the ground handling of mating the two vehicles. The first Trans-atlantic mail plane for the Brits did this, with two 4 engine aircraft stacked on top of each other. Yeah, it'd work, and like this concept it would be more "efficient". But it's just so darn much easier to operate something that you just put fuel in and let fly. Even if the payload wasn't that much as a percentage of tare weight and fuel, it's just so much easier to tank it up.
I did a bit searching on the net on the early proposals for the shuttle from the late 60's, early 70's. Obviously it was damaged because NASA insisted that it be able to haul up large components. That might be nice, but you just don't need an 18 wheeler every day. They had the Saturn V for that. Dummies.
