The German Type XXI submarine — more sophisticated than any of the Allied boats — was reverse engineered by both countries and the technology was inserted into later attack boats. Technology from the XXIs — like snorkels to refresh the air in the boat and new types of sensors — led up to the next major step in submarine development. In 1955, the atomic powered USS Nautilus set a record for remaining under water on a trip to Puerto Rico. The trip did two things: threw down one (of several) technological gauntlets to the Soviets during the Cold War and completely changed how submarines could be thought of as weapons. Hyman Rickover, perhaps the US Navy's crankiest admiral (he called Edward R. Murrow and Diane Sawyer both dumb, to their faces in interviews), pioneered the idea of the nuclear submarine and guided the Nautilus program.