Abstract: Thermal control of powered systems on-board a flight vehicle is achieved by leveraging the latent heat storage capacity of Phase Change Materials (PCMs) to maintain the operating temperature at or slightly above the melting temperature of the PCM. The invention is particularly well suited for use with powered systems such as laser, microwave emitters, RF sensors and high-density power electronics that must operate at a desired operating temperature while generating considerable waste heat in a confined packaging volume of smaller flight vehicles such as missiles, rockets, guided projectiles, drones or other such platforms.