One of the most significant challenges in the development of an autonomous human-scale robot is the issue of power supply. Perhaps the most likely power supply/actuator candidate system for a position or force actuated human-scale robot is an electrochemical battery and dc motor combination. This type of system, however, would have to carry an inordinate amount of battery weight in order to perform a significant amount of work for a significant period of time. A state-of-the-art example of a human scale robot that utilizes electrochemical batteries combined with dc motor/harmonic drive actuators is the Honda Motor Corporation humanoid robot model P3. The P3 robot has a total mass of 130 kg (285lb), 30 kg (66 lbs) of which are nickel-zinc batteries. These30 kg of batteries provides sufficient power for approximately 15–25 min of operation, depending on its workload. Operation times of this magnitude are common in self-powered position or force controlled human-scale robots, and represent a major technological roadblock for designing actuated mobile robots that can operate power-autonomously for extended periods of time. The mono propellant-powered actuation system is similar in several respects to a typical pneumatically actuated system, but rather than utilize a compressor to maintain a high-pressure reservoir, the proposed system utilizes the decomposition of hydrogen peroxide (H2O2) to pressurize a reservoir. Peroxide decomposes upon contact with a catalyst. This decomposition is a strongly exothermic reaction that produces water and oxygen in addition to heat. The heat, in turn, vaporizes the water and expands the resulting gaseous mixture of steam and oxygen. Since the liquid peroxide is stored at a high pressure, the resulting gaseous products are similarly at high pressure, and mechanical work can be extracted from the high-pressure gas in a standard pneumatic actuation fashion.