But the importance of the lifting properties of a body that is descending into the upper atmosphere still stands today. Sänger’s work and his wife’s calculations proved significant in the design of the North American X-15 rocket plane, the X-20 Dyna-Soar and eventually in the design of the Space Shuttle. In October 1985 the Messerschmitt-Bölkow-Blohm (MBB) Organization renewed studies of the Sänger system as the core of a two-stage spacecraft with horizontal take-off. The first stage would propel the plane to high speed and would then be jettisoned, allowing the second stage to fire and carry it further towards space. In my view, this would make great sense, and I have extolled the widely unrecognized ingenuity of Sänger in the television series Weird Weapons of World War II for the History Channel. My view is that the present method of launching a rocket is excessively wasteful of fuel, for the energy is used to support the mass of the rocket as it gathers velocity. Launching the rocket on wheels, running on a ramp that later curves upwards to launch the rocket aloft, is a clear design advantage; for then it is the track which supports the weight, rather than the rocket thrust. It would be possible for the rocket to achieve high launch speeds by running horizontally before its path turned upwards, conserving onboard fuel for the entry into space. Who knows? Those secret ideas from World War II may yet find realization.
CHAPTER 3
FLYING WEAPONS: BOMBS AND MISSILES
As we have seen, there were impressive and powerful developments in aircraft technology in World War II. However, the description ‘flying weapons’ is not restricted to aircraft. Many of the strangest secret devices of the war were airborne weapons, and some of them were of an incredibly advanced design.
Barnes Wallis was a crisp and authoritative figure with a warm, avuncular manner when I met him in the 1970s at the BBC in London. His proposal as World War II enveloped Europe was to construct increasingly massive bombs. Wallis argued that the best way to bring the German war machine to its knees was to disrupt its capacity for weapons production, and he had in mind the huge factories in the Ruhr. He realized that the Nazis would seek to construct massively reinforced concrete bunkers that would be impregnable to conventional explosives, and proposed huge bombs that would bring about the desired level of destruction. Wallis decided on a 10-ton bomb that would be dropped from high altitude and demolish the most heavily reinforced construction by penetrating deep inside the ground before it detonated and erupted from beneath. In 1940 he revealed his proposal for a 22,400lb (10,200kg) bomb that could even bring down the massive dams on which German industry relied.
The Air Ministry conceded that the idea was viable, but it failed because there was no aircraft large enough to carry such a weapon. Barnes Wallis responded by designing just such an aircraft, the Victory bomber. It was designed to be 96ft (23m) long with a wingspan of 172ft (52.4m), designed to fly at an altitude of 34,000ft (10,000m) at a cruising speed of 352mph (566km/h). This was an astonishing concept: the American B-245 Liberator in comparison cruised at 214mph (344km/h) at a maximum altitude of 28,000ft (8,534m). Barnes Wallis’s new aircraft would carry a gun turret with four weapons, but it was otherwise undefended since it would easily out-fly any other aircraft in existence. Nonetheless, in May 1941 the project was rejected. The Air Ministry concluded that the bomber would have only one purpose, and expensive fixed-mission projects were not something the British government wished to support. Furthermore, it was calculated that the aircraft was so revolutionary that it was unlikely to be operational before the end of the war.
The refusal of the Air Ministry to give the go-ahead to the Victory bomber left Barnes Wallis with the ambition of finding alternative ways to destroy the German factories in the Ruhr. This had been an aim of British Intelligence since about 1937, and sketchy plans to bomb the dams above the factories were in mind prior to the outbreak of hostilities. The central focus was the Möhne dam, which was known to be well defended, but which Barnes Wallis knew could be destroyed with his proposed 10-ton bomb, if only there was a plane to carry it. The only feasible alternative was to use large torpedoes that could detonate against the dam wall itself, but the Germans were aware of the risk and had the dams of the Ruhr well protected by heavy-duty submerged nets. Wallis walked along the sea-shore one day, skipping stones across the surface, and suddenly thought of the notion of designing a bomb that would similarly ricochet across the water in the reservoirs — above the protective nets — and impact on the concrete dam itself. His proposal was for a cylindrical bomb, spinning backwards to the direction of travel, which would be dropped from a low-flying aircraft. The backward spin — coupled with the forward speed of the bomb — would cause it to bounce across the surface. If it struck the dam wall, the backwards spin would cause the bomb to hug close to the dam as it sank, and a pressure-sensitive hydrostatic fuse would detonate it at the optimum depth. The backspin would also slow the forward motion of the bomb with each skip, so that it would fall behind the aircraft and reduce the chances of damaging the low-flying plane that had dropped it.
The Royal Air Force was sceptical at first, but Barnes Wallis persisted and produced movie films of his successful experiments. In early June 1942 he experimented with a mine suspended on scaffolding to test the effect of underwater detonations. He destroyed the disused Nant-Y-Gro dam near Rhayader, in central Wales, with a submerged 279lb (127kg) mine, to help ascertain the way a dam might behave under attack. Dummy versions of the bombs were then dropped from a modified de Havilland Mosquito B Mark IV aircraft off Chesil Beach, near Weymouth Bay in southern England, but they burst apart on hitting the water and Wallis asked Wing Commander Guy Gibson if they could be launched from a lower altitude — 50ft instead of 120ft (15m instead of 36m). Gibson agreed and there were subsequent tests of dummies on the dams in the Elan Valley, Wales. In February 1943 the Air Ministry finally accepted the scheme and it was resolved to bomb the dams of the Ruhr in springtime, when the water in the reservoirs was at its highest. The mission was code named Operation Chastise and was given to No. 617 Squadron flying out of RAF Scampton, Lincolnshire, with Gibson as the leader. The Lancaster bombers carried out extensive training and numerous dummy runs, until they were accustomed to flying over the kind of landscape that they would encounter on the raid and made several successful practice runs along the Upper Derwent Valley in Derbyshire. This was dangerous work; the flying was under a full moon at night, no more than 60ft (18m) above the surface and they knew that the target would be some 400 miles (640km) away from their base. The pilots became proficient at straight and level flight only some 30ft (less than 10m) above the ground — little more than the height of a house.
The bombers were mechanically adapted to carry the weapons and were fitted with electric motors to set them spinning, prior to the drop. Barnes Wallis knew that it was vital for the bombs to be launched a precise distance from the dam wall, or they would simply skip over the top. To facilitate this he designed a simple Y-shaped wooden sight which the bomb aimer would use to line up the two ends of the dam. Paired downward pointing lights were carefully positioned, so that the two beams met when the plane was at exactly the correct height above the surface of the water. With the dam in the bomb-aimer’s sights, and the beams correctly aligned, the bomber was certain to fly within the very narrow tolerances that the mission demanded. As the teams kept practising, many of them worked out their own ways to adapt the apparatus to suit their own preferences. One answer was to tie string on struts on the windscreen, pulling it back like the elastic on a catapult, to give the range of the towers at either end of the dam.