The Kasatka class was a class of submarines built for the Imperial Russian Navy. The six boats were built between 1904 and 1905. They were designed by I. G. Bubnov and were based on the . The first boat, , experienced significant problems with stability on trials and had to have extra flotation added. In 1905, four of the class were transferred from Western Russia to Vladivostok with the outbreak of the Russo-Japanese War. Initially powered by a kerosene/electrical system, the boats were re-built around 1910 with a diesel-electric power plant following the end of the war. The class remained in service throughout World War I. Two were captured by the German Empire in 1918 and handed over to the British following the German surrender. They were scuttled by the British in 1919 to prevent their capture by the Soviets. The remaining four were broken up for scrap in 1922. Design and description I. G. Bubnov was tasked with producing a submarine design following experience with the , which had been deemed a success. The design was accepted by the Naval Technical Committee on 20 December 1903. As designed the class had a surfaced displacement of and displaced when submerged. They were long with a beam of with a draught of . The submarines were propelled by one shaft powered by a kerosene engine for travel on the surface rated at and an electric motor rated at . The Kasatka class had a maximum speed of on the surface and submerged. Initially the design called for a three-shaft propulsion system, but due to the increased hostilities with the Empire of Japan, the submarines were completed with only the one shaft-design. They had a range of at surfaced and at submerged. The class was armed with four torpedoes carried externally in Drzewiecki drop collars and one machine gun. Vessels of the class had a complement of 24. Modifications In 1906–1907, new conning towers were installed aboard the submarines to rectify buoyancy issues. In 1910, the Kasatka class were rebuilt with new power plants. They received a diesel-electric system which included a diesel engine rated at . The displacement of the submarines increased to surfaced and submerged. Two of the class, Nalim and Skat, were given a gun in 1915. Ships Service history The first submarine of the class, Kasatka was ordered in the 1903 building programme on 2 January 1904, with