30 which supplies propellants such as a fuel and an oxidizer which form a reacting mixture the reacting mixture is created by intimately mixing the propellants by the injector system 28 one injector system 28 may have a geometry selected based on the degree of mixing for example the geometry of the injector system 28 may include impinging jets swirl elements pre mixing chamber and other features that provide for intimate mixing of the propellants in one non limiting embodiment the fuel includes ethylene and the oxidizer includes oxygen the annular combustion chamber 22 is open opposite the injector system 28 to define a nozzle 32 an initiation system 34 is utilized to ignite the spinning detonation wave in one embodiment an initiation system 34 may include a mixing chamber 36 a spark plug 38 and a tangential detonation tube 40 in another embodiment not shown herein the initiation system 34 may use devices to ignite combustion including a pyrotechnic ignitor a glow plug hypergols and pyrophoric fluids and others in lieu of or in addition to the spark plug 38 in another embodiment the initiation system 34 may include detonation cord exploding wires and or a local ignition system disposed proximate the injector referring again to fig1 a relatively small amount of propellants are premixed in the.