REL has been developing Skylon since the 1990s, and has done nothing but suck up research dollars ever since. It hasn't ever created a testable engine, let alon

REL has been developing Skylon since the 1990s, and has done nothing but suck up research dollars ever since. It hasn't ever created a testable engine, let alone a testable plane. The whole idea is a set of nearly insurmountable problems. For just one example, they claim that it will be an enormous plane filled with hydrogen, so on re-entry it will have a large cross section but low mass so it will be slowed by atmospheric friction more rapidly than the shuttle. But it's also going to have wings and turbulent air flow, it's a bad shape for atmospheric re-entry. This is project killer if they can't handle re-entry, and they are no where near a physical test of it.