Pluton carried an auxiliary boiler to heat or cool the magazines and to produce drinking water, alongside her four main boilers. Her fuel capacity initially suggested an endurance of about 7,700 nautical miles at 14 knots. That figure had to be revised downward because the auxiliary machinery consumed much more power and fuel than the designers had allowed. The basic fast-minelayer concept remained useful despite this engineering miscalculation. Endurance depended on magazine conditioning and water production as well as propulsion, and the designers badly underestimated those auxiliary demands.
Notable Point · 40:56-42:14
How auxiliary loads cut Pluton's practical range
Magazine conditioning, drinking-water production, and other auxiliary demands turned an impressive calculated endurance into a much shorter practical range.