Headway in rocket development came in Japan. Fearing American bombers after the attack on Pearl Harbour in December 1941, Japanese scientists at the Naval Technical Research Unit produced solid-fuel rockets that could be used as surface-to-air missiles. Their size varied from 10lb to 55lb and they were called ‘Funryu’. The first version was less than reliable but the second version was a lot better. It could reach an altitude of three miles. Version 4, produced far too late in the war to allow for any meaningful production, could reach an altitude of 20 miles. Both Mitsubishi and Kawasaki were also involved in rocket development – small rockets that targeted a plane’s machine guns as an audio-sensory device on board detected the guns shock waves. However, such was the damage caused by American bombing of factories etc, that both firms did not have the ability to mass produce these rockets and their were production was cancelled in early 1945.
The Japanese also developed the kamikaze ‘Ohka’ rocket plane. First thought of in 1943, it came into production in 1944 and was first used in war in April 1945. The ‘Ohka’ was carried by a mother plane to within 50 miles of its target. After being released from the plane, the ‘Ohka’ glided towards its intended target at about 250 mph. Large fins gave the ‘Ohka’ stability and allowed the rocket plane to stay on target. As it approached its target, the pilot ignited three rockets that burned for 10 seconds but increased the speed to over 600 mph. At this speed it was unstoppable – but also highly unstable. If it hit its target, the 2,645lb warhead could do much damage. However, such was its unstable final phase that the Americans nicknamed the weapon ‘Baka’ – which means fool in Japanese.