The Japanese also developed the Type 10 Rocket Motor which was a simple propulsion unit intended as a launch facility for aerial bombs. They later produced a rocket 18in (44.7cm) in diameter; it was an unsophisticated projectile that was used in action on Iwo Jima and had a maximum range of over a mile (2,000m). Although it was inaccurate, it delivered a warhead of 400lb (180kg). Interestingly, this rocket was also spin-stabilized. This rotation around the axis had the potential to stabilize a rocket in flight, just as the Congreve rocket had in a previous century.
The Imperial Japanese Army focused their efforts on developing an air-to-surface missile while the Navy concentrated on the design of surface-to-air missiles. The Army decided to develop their Igo missile, while the Navy’s project was the Funryu (Raging Dragon) rocket.
The Igo-1-A was a winged cruise missile constructed by Mitsubishi from wood and metal. It was 16ft (5.77m) long, and had a wingspan of 10ft 9in (3.6m). It had a launch weight of 3,080lb (1,400kg) and could deliver a 1,760lb (800kg) warhead at a velocity of 340mph (550km/h). The rocket motor was a Mitsubishi Tokuro-1 Type 3 which fired for just 75 seconds. There was also an Igo-1-B produced by Kawasaki which was of similar design but delivered a somewhat smaller payload. Both versions of the Igo-1 were launched from an aircraft at about 5,000ft (1,500m) some 6 miles (about 10km) from the target. An onboard altimeter established the missile on a straight and level path and it was then radio-controlled by the pilot to the target. The missiles left no smoke trail and it was difficult for the aircraft pilot to aim them accurately. The rockets were fitted with a tail light for use at night — but under these conditions, although the pilots could see the drone, they now had difficulty in seeing the target. The final refinement of the Igo rocket was the Igo-1-C, developed by the Aeronautical Research Institute of Tokyo Imperial University. Rather than being guided by radio, the Igo-1-C was ingeniously designed to home in on the shockwaves produced by ships when they fired their guns.
Meanwhile the Navy were developing their Funryu rockets, and planned to produce four versions. Like their Igo counterparts, they would be radio-controlled to the target. In the event, only the Igo-1-A and Igo-1-B went into production, and none was ever fired at the enemy.
Air-to-ground missiles were not seriously considered by the Japanese until March 1944. The Army continued to prefer spin-stabilized rockets, while the Navy wanted devices stabilized by fins. Had the two services combined forces, an optimized design could well have been agreed but, as it was, the age-old rivalry persisted and each service pressed ahead with their own ideas. The air-to-ground missiles were to be fitted to the Kawanishi N1K-J Shiden (Violet Lightning) aircraft which were to be specially modified to carry six of the rockets ready to attack the fleet of ships that the Japanese believed to be on its way to invade the homeland. In the event, the aircraft never achieved full operational status before the war’s dramatic end. Japanese plans to fire off a salvo of rockets were never achieved; instead each rocket was launched singly, in the manner of firing off a mortar, and so little useful benefit was ever achieved.
British interest in rockets was far more modest than that in Germany. At the beginning of the war, small 3in (7.6cm) diameter rockets powered by cordite were all that were available. By the end of 1940, a larger 8in (20cm) version had been developed that could be fired in volleys of 128 rockets from a rack known as a ‘projector’. There were many practical problems, and the organization of such a rocket battery had to be worked out from first principles, since there was no practical experience from which to work. On 20 May 1940, in the back room of a public house at Aberporth in Wales, a meeting was convened by the local Ordnance Director and it was decided to try using these batteries of rockets as a routine measure against enemy aircraft. Within weeks a firm in Greenwich, London, named G. A. Harbey had been contracted to mass produce the ‘projector’ racks and by September over 1,000 had been manufactured.
The following month, Churchill’s son-in-law Duncan Sandys (then a major) organized a rocket section to defend the strategic port of Cardiff with 3in rockets, and the first German plane was brought down on 7 April 1941. By the end of 1941 there were three such facilities, known as ‘Z-batteries’, in existence. Two were at Cardiff, and the third was at Aberporth where there is to this day a missile testing range. The UP-3 rocket, as it was then known, was further improved and eventually emerged as a 6ft (1.8m) rocket with a lethal radius of up to 70ft (21m). By December 1942 there were 91 batteries in existence, despite enemy raids which twice razed the factory producing the rocket fuses. A modification of this rocket was produced as an operational surface-to-air missile capable of reaching 1,000mph (1,600km/h). Although the Army showed little interest in these missiles, the Navy began production of six-unit ‘Mattress’ projectors for use at sea. They were used in the landings in Sicily and mainland Italy which were to ensue. After further tests at Sennybridge (also in Wales) the Army began to change its mind and a Land Mattress projector was produced which went into service with Canadian troops when they fought for the Rhine and Scheldt rivers. Towards the end of the war, the Stooge rocket was unveiled. It was designed specifically to attack enemy aircraft, particularly (as it happens) the Japanese suicide squads. This was a 740lb (335kg) 10ft (3m) radio-guided missile with a range of up to 8 miles (13km). It had a top speed of 500mph (800km/h) and delivered a 220lb (100kg) warhead. The British rocket had come of age.
Not all the rocket trials were a success. In 1942 a rocket-assisted take-off was due to be demonstrated on a Stirling bomber. A clutch of senior RAF officials were in attendance, one of them reporting directly to Churchill. Expectations were high — if successful this would allow heavy bombers to take off from small airfields, even when fully laden. Twenty-four rockets were secured beneath the wings, and a variable rheostat — a device that could progressively increase electrical current — had been installed to fire the rockets in strict sequence as the throttles were opened. On a given signal, the plane roared into life and suddenly, as it began to move forward, there was a shattering explosion and the air filled with rockets and parts of the aircraft. The rockets had fired too closely together, exerting stresses that the aircraft had never been designed to withstand. When the smoke cleared, the wreckage of the plane was left stranded on the runway, its wings and engines pointing in all directions. The pilot, miraculously, walked through the smoke unharmed — just weeks before, his previous bomber had crashed in flames, and he had walked away from that, too. He was Squadron Leader Harold Huxtable, one of the luckiest pilots of World War II.
Even the most successful of the British forays into rocketry were no match for the Germans in terms of high-technology development. The British designs were intended mainly as weapons of defence, and there had been no interest shown in offensive weapons of a large scale.
Like the British, the Americans largely relied on solid-fuel rockets during the early years of World War II. The first truly successful American rocket of the war arose from the vestiges of research carried out by Robert Goddard at the end of World War I and was also one of the smallest — the bazooka. Development had been driven largely by the need to find an answer to the otherwise insurmountable problem of recoil, which occured when an armour-piercing shell was fired from a transportable gun. So fierce was the equal-and-opposite reaction that it seemed impossible to design a suitable weapon that could be moved around by soldiers on the battlefield. As Goddard had demonstrated in 1918, a rocket-propelled missile would overcome the difficulty since the motive force is generated during flight and is not due to the massive reaction of an exploding cartridge. In 1942 Clarence Hickman, Goddard’s former colleague, resumed experiments at the George Washington University in Washington DC, and Lieutenant Edward Uhl — who was later credited with being ‘The Father of the Bazooka’ — developed a launcher tube that could be put into production. After almost a quarter-century in the doldrums, Goddard’s invention was suddenly a high priority.