PURPOSE: To obtain a small-sized light-weight missile effectively cooling electronic parts in case of emergency by fitting two compounds generating endothermic chemical reaction through mixing, two hollow chambers receiving these substances and an initiator breaking the partition walls of hollow sections by an external signal to the guided missile on which a plurality of electronic modules incorporating the electronic parts requiring cooling are loaded.

CONSTITUTION: A plurality of electronic modules 1 constituting a guided missile are constituted by rectangular hollow cylindrical bodies, and electronic parts 6 requiring cooling are each fixed inside the long sides of the modules 1. Two partitioned hollow sections 7a and 7b are formed in the wall of the cylindrical module 1 on the side to which the parts 6 are fastened, liquid ammonia 8a and urea 8b are each sealed previously in the hollow sections, and an initiator 9 is buried previously between the hollow sections 7a and 7b. According to such constitution, the initiator 9 is exploded by signals 10 from an oscillator 11 as required to communicate the hollow sections 7a and 7b, ammonia 8a and urea 8b are mixed to generate an endothermic reaction, and the parts 6 are cooled rapidly.