Microwave‐Controlled Solid Propulsion: Mechanisms, Materials, Actuation Strategies, and Pathways to Digitally Throttleable Rocket Motors

Significant success has been achieved in the area of microwave‐controlled solid propulsion starting from investigations in the realm of passively boosting burn rates to active microwave‐controlled propulsion with a digital controller. This review discusses recent advancements in the combination of microwaves with different propellant materials through such phenomena as plasma‐aided combustion, eddy current heating of conductive particles, switching susceptors made of graphene, and microwave‐assisted formation of porosity. Burn rate modulation, ignition‐extinction cycles, and local burn rate amplification by up to six times have been observed using electromagnetic actuation. Multiphysics simulation and diagnostics reveal the physics underlying burn rate modulation in alkali‐doped AP/HTPB propellants, embedded antenna arrays, and reduced graphene oxide‐encapsulated thermites, which provide localized energy delivery and fast ignition capabilities. Current research directions include trade‐offs related to dopants, cavity detuning, scale‐up to rocket motor geometries, electromagnetic interference, power‐system design, and compatibility with additive manufacturing techniques. The emphasis lies on solid propulsion‐specific aspects of controllability, energy efficiency, and reliability. Last, research roadmaps are outlined for next‐generation solid rocket motors.