 However, he kept considering the problem after the contract had finished, and eventually developed a tubular device, designed to run underwater on its own, and powered by compressed air.The result was a submarine weapon, the "Minenschiff" (mine ship), the first modern self-propelled torpedo, officially presented to the Austrian Imperial Naval commission on 21 December 1866.The first trials were not successful as the weapon was unable to maintain a course at a steady depth.