shows the time response of the heat pipe for different heat input. The time response is obtained while the outer surface temperature reaches 180 C. These time constants can be used to determine how fast a heat pipe responds to an applied input power and depends on the heat transfer coefficient. As shown, increasing the heat transfer coefficient can greatly reduce the time constant. The heat pipe response is faster with higher heat flux. An outer surface temperature of approximately 167 C is obtained in steady state condition with a heat input of 140 W.