One of the current interests in the hypersonic propulsion system is the detonation engines which offer significant advantage in cycle efficiency. Past development in detonation engines has mainly focused on pulsed detonation engines (PDE), where intermittent 1-D combustion across a shock propagating in a tube is made feasible by complicated valving arrangement. Continuous detonation engines (CDE) have marked advantage over PDE in that combustion occurs across a shock wave spinning continuously along the circumference of the tube, thus eliminating valves. In addition, CDE can replace high pressure compressor stages. CDE is envisioned to be used between Mach 2 and 4+, filling a gap between gas turbine engine and scramjet. Both theoretical and experimental investigations are being carried out by M. Kurosaka and Carl Knowlen.