Pittsburgh-based Astrobotic has completed a successful series of hot-fire tests of its rotating detonation rocket engine prototype Chakram, marking a key milestone toward bringing the experimental propulsion technology to flight readiness. Rotating detonation rocket engines (RDREs) work differently from conventional designs. Typical rocket engines rely on a steady, controlled process of chemical propellant ignition inside a combustion chamber. RDREs use a continuous, circular detonation wave that travels around a ring-shaped chamber, which produces higher pressure and efficiency and results in increased thrust with less fuel. In theory, that can improve efficiency by around 10–15%, while also reducing engine size and weight — advantages that are especially important for spacecraft, where every ounce of weight needs to be accounted for. But the benefits have been difficult to realize in practice.…