The US Navy specification for the device included simple controls and automated operation by one person, along with a 30 hp output – sufficient to give a 20-tonne submarine a speed of 8 knots. The closed-loop nature of the engine's operation required precise matching of the quantities of diesel fuel and oxygen injected into the flow of exhaust gases, themselves accurately controlled for volume, temperature and water content. Compressed air was used to start the Perkins four-cylinder diesel so as to avoid the risk of an explosive mixture of oxygen, and the finished power pack had three times the power to mass of batteries and could power a 10-tonne submersible for 16 hours at 6 knots.
