History of submarines few years before the US, and paralleled subsequent US development in this area. In the 1950s, nuclear power partially replaced diesel-electric propulsion. The sailing of the first nuclear-powered submarine, the USN ""Nautilus"" in 1955 was soon followed by similar British, French and Russian boats. Equipment was also developed to extract oxygen from sea water. These two innovations, together with inertial navigation systems, gave submarines the ability to remain submerged for weeks or months, and enabled previously impossible voyages such as the crossing of the North Pole beneath the Arctic ice cap by the USS "Nautilus" in 1958. Most of the
Pole to Pole flying there on a small aeroplane fitted with skis. The North Pole scene was filmed in May 1992, after the rest of the series had been shot, as weather conditions were more suitable then as the ice was too fragile the previous year. From there, he heads to Greenland, then the Norwegian island of Spitsbergen, where the towns of Ny Ålesund and Longyearbyen are located. From there he sails across the Barents Sea on a supply ship to the Norwegian port city of Tromsø, where he visits a statue of Roald Amundsen, the first man to reach the South Pole.