units of rocket fighters around Berlin, the Ruhr and the German Bight. A typical Me 163 tactic was to fly vertically upward through the bombers at , climb to , then dive through the formation again, firing as they went. This approach afforded the pilot two brief chances to fire a few rounds from his cannons before gliding back to his airfield. It was often difficult to supply the needed fuel for operating the rocket motors. In the final days of the Third Reich, the Me 163 was withdrawn in favor of the more successful Messerschmitt Me 262, which used jet propulsion instead. Other German rocket-powered aircraft were pursued as well, including the Bachem Ba 349 "Natter", a vertical takeoff manned rocket interceptor aircraft that flew in prototype form. Further projects never even reached the prototype stage, such as the Zeppelin Rammer, the Fliegende Panzerfaust and the Focke-Wulf Volksjäger. Having a much larger size than any other rocket-powered endeavor of the conflict, the Silbervogel antipodal bomber spaceplane was planned by the Germans, however, later calculations showed that design would not have worked, instead being destroyed during reentry. The Me 163 Komet is the only type of rocket-powered fighter to see combat in history, and one of only two types of rocket-powered aircraft seeing any combat. Japan, who was allied to Nazi Germany, secured the design schematics of the Me 163 Komet. After considerable effort, it successfully established its own production capability, which was used to produce a limited number of its own copies, known as the Mitsubishi J8M, which performed its first powered flight on 7 July 1945. Furthermore, Japan attempted to develop its own domestically designed rocket-powered interceptor, the Mizuno Shinryu; neither the J8M or the Shinryu ever saw combat. The Japanese also produced approximately 850 Yokosuka MXY-7 Ohka rocket-powered suicide attack aircraft during the Second World War, a number were deployed in the Battle of Okinawa. Postwar analysis concluded that the Ohkas impact was negligible, and that no U.S. Navy capital ships had been hit during the attacks due to the effective defensive tactics that were employed. Other experimental aircraft included the Soviet Bereznyak-Isayev BI-1 that flew in 1942 while the Northrop XP-79 was originally planned with rocket engines but switched to jet engines for its first and only flight in 1945. A rocket assisted P-51D Mustang was developed by North American Aviation that could attain 515 mph.