Design
Under the leadership of Admiral Hyman G. Rickover, Naval Reactors followed a concurrent design strategy, with the design and construction of the S1W reactor taking place ahead of the design and construction of the Nautilus. This enabled problems to be identified and resolved before they appeared in the shipboard plant. To better support this design process, the S1W power plant was built inside of a submarine hull. While the cramped spaces prevented engineers from obtaining information on some plant components, it provided a much more realistic example of how the shipboard plant would have to be constructed.
Read more about this topic: S1W Reactor