downstream of the point of propellant injection several methods for initiating a detonation cycle may be used detonation may be initiated by igniting a fuel oxygen mixture in a small detonation tube not illustrated that discharges into the detonation chamber or by igniting a fuel oxygen mixture collocated within the detonation chamber alternatively a high voltage electric discharge or pyrotechnic igniter can be used the small detonation tube method generally requires fuel an oxidizer pumps high speed fluid valves an electronic controller a power supply and a spark generator the direct electric discharge method generally requires a spark plug an electronic controller and a power supply laser ignition can be used where a laser produces a high energy beam initiating detonation of propellant in the detonation chamber in one embodiment of the present invention relatively low detonation velocities e g from about 1 to 5 km s are employed conventional detonation velocities range from about 6 to 8 km s various techniques may be used for controlling detonation velocities one technique for limiting detonation velocity is selecting a detonation chamber geometry to limit the detonation wave propagation another technique is to provide additives to liquid propellants that will reduce detonation wave velocity and pressure yet another technique is.