New York class: propulsion redundancy as survivability

The New York class used only two shafts, a layout presented as an avoidable weakness in an otherwise ambitious battleship. A slightly longer hull, more boiler power, and four shafts might have increased both speed and resilience. In a two-shaft ship, a torpedo hit or damage to one machinery space could remove half the available propulsion. With four shafts, comparable damage might cost only a quarter, leaving more ability to manoeuvre under fire. The extra machinery would add weight and occupy space, but that penalty bought insurance against the especially dangerous loss of battleship mobility.