Sounds complicated, right? And yet the ESA reviewed and passed this project, which means the next step is to build a working prototype of the engine. Sounds far out to me, but the concept does have some merit. If the Skylon has to carry a minimal amount of oxygen on board to achieve orbit, that makes room for more people, research equipment, and what have you. Right now the heaviest cargo on the soon-to-be-retired space shuttles is the actual fuel itself. Another bonus? Hydrogen is the most abundant element in the universe. This technology could prove to be a huge boon in humanity’s quest to conquer the stars.