Vandal's three constant-speed engines fed an electric transmission that varied propeller speed, making control simpler than direct drive with the machinery then available. Early French submarines paired a 150-horsepower diesel for surface running with a 130-horsepower electric motor underwater and carried externally launched torpedoes. Their modest surface and submerged speeds, range figures, and 14-person crews show the scale at which the technology first entered service. Diesel engines first thrived where efficiency mattered most: economical merchant operation and reliable power generation inside the limited space of a submarine pressure hull.
Notable Point · 35:59-42:32
Diesel-electric power and submarine space
The Vandal and early French submarines show why diesel favored efficient merchant operation and compact submarine power plants.