Directed energy weapons under development by the Air Force and others can impose both high heat flux and large overall heat load demands on their cooling systems, up to 1000 W/cm2 and 100 kW respectively. TDA proposes to implement an ammonia-based spray cooling system to meet these demands. Our system is a novel two-phase thermal cycle that avoids the disadvantages of both mechanically pumped loops and heat pipes. This thermal management system is essentially passive, using self-generated fluid forces to promote the circulation of the working fluid, thereby eliminating the weight and power draw penalties associated mechanically-pumped systems as well as providing sufficient fluid pumping pressure capability to implement high heat flux spray cooling with insensitivity to g-loading. The proposed high heat flux cooling technology is applicable not only to heat removal from military directed empergy weapons but to high-power commercial eletronics, communications, computer and power-management markets. In addition, smaller versions of the cooling cycle are useful in cooling high performance chips and multi-chip modules.