Detonation is shock-induced combustion, which is intrinsically more efficient than slower burning deflagration. One of the most promising detonation engines is the continuous rotating detonation engine (CRDE) , where fuel is burned by transverse shock waves spinning in an annulus. The high pressure behind the shock drives the shock to spin and at the same time forces the burned gas to exhaust at high speed. The shock also acts as a ‘bladeless’ compressor. The CRDE is a pressure gain combustor, which also contribute to produce thrust.