“U.K. aerospace manufacturer Reaction Engines is preparing a potentially revolutionary rocket engine for a real-world test within the next 18 months.

The Synergistic Air-Breathing Rocket Engine (SABRE) runs partially on oxygen collected from the atmosphere rather than relying on heavy fuel. That means serious weight savings, according to the European Space Agency — such that a payload could be delivered to orbit at “half the vehicle mass of current launchers.”…”