I am hoping they get somewhere with the single stage to orbit stuff such as the Skylon project using the SABRE engine. I don't really understand how it all works, but I think it pulls oxygen from the air, compresses and cools it, then mixes with onboard hydrogen and burns it. Apparently in lower altitudes it can function like a regular jet engine, but at high altitudes it functions as a rocket
https://en.wikipedia.org/wiki/Skylon_(spacecraft)https://en.wikipedia.org/wiki/SABRE_(rocket_engine)