Buildable but surely far too complicated?? It looks like one of those concepts that although it would work would surely be a swine to operate and fly. Three different engines and fuel systems would make the thing pretty big as well but with limited passenger space.
Funnily enough I'm just past the part in Ben Rich's SkunkWorks where he criticised Reagans adminsitration for announcing a hypersonic plane saying it'd most likely be the latter half of this century before such thing would be possible, if ever.
