Among the pioneers of this alternative solution was the very first submarine of the Swedish Navy, HMS "Hajen" (later renamed "Ub no 1"), launched in 1904. While its design was generally inspired by the first submarine commissioned by the US Navy, USS "Holland", it deviated from the latter in at least three significant ways: by adding a periscope, by replacing the gasoline engine by a semidiesel engine (a hot-bulb engine primarily meant to be fueled by kerosene, later replaced by a true diesel engine) and by severing the mechanical link between the combustion engine and the propeller by instead letting the former drive a dedicated generator. By so doing, it took three significant steps toward what was eventually to become the dominant technology for conventional (i.e., non-nuclear) submarines.