>>1113635>What is the optimum size and weight for a space plane? Could you design a hypersonic aircraft to reach orbital velocity in the atmosphere so it could use atmospheric oxygen as the oxidizer for it's fuel?Yes and the most notable attempt to do that is Reaction Engines' SABRE program, whose engines are dual-mode (can burn both atmosphere or stored fuel). However, this is very complex and very expensive and in the end a single-stage-to-orbit vehicle would be difficult to make and maintain, especially if it has to take off and land from normal runways. This is why the AF has long endorsed a dual-stage-to-orbit system, much like Boeing is now building with the XS-1 Phantom Express (pic related).
