I probably wouldn't be surprised by folks' knowledge of old James Blish novels.... I read "Cities in Flight" when I was but a wee lad in the late sixties, I think.... I have to admit I'm a little lost about the two names twice comment. Actually, the engines do have a tiny hole inside them with a big flange at the end; I should render a shot looking down them. But maybe a grille or something would be just as good. The biggest problem I have with the size of the engines is that it looks like the whole thing would rock back on its landing pads if the engines are heavy. Could make for an amusing animation of a landing sequence, though.