Regarding a jet that converts into a rocket above the atmosphere so that the occupants don't all have to have the health of an Olympic athlete, check out Skylon
At the moment the idea is for it to be an unmanned cargo carrier, partly because not having to worry about crew/passenger lives in the prototype versions makes things so
much easier and cheaper. At the talk I went to by Alan Bond a few weeks ago he said it would be feasible to put a habitation pod in the cargo bay, but realistically a passenger version would be a major design revision.
To give you an idea of the projected benefits of a plane like this, they are anticipating a hardware cost of about the same as a jumbo jet, and an initial mission cost of $5 million, as against well over $100 million for disposable craft or the shuttle. And the whole
thing is designed to be re-usable after a few days' check-over.