The characteristics of LACE, or a liquid air cycle engine, for hypersonic airbreathing propulsion is discussed. Both air and hydorgen are pumped up to a high pressure in the liquid phase; the liquid air and gaseous hydrogen from the heat exchanger (air condenser) are burned in a rocket chamber and are expanded in a normal propelling nozzle. With the speed range up to a Mach number of 10, LACE can be found to maintain its superiority over the rocket concering the specific impulse.