In August 1944 the Chief of Development for the German Air Ministry (Reichsluftfahrtministerium), Colonel Siegfried Knemayer, was asked for new proposals for a hard-hitting plane that would be difficult to disable, and he listed the criteria that such an aircraft should satisfy. The result was the Natter. Knemayer decided to take a cheap rocket-powered aircraft that could fly near the speed of sound, fit it with armaments, and blast it from a vertical launch to attack enemy planes. A full set of control surfaces and landing gear would not be necessary, as the pilot would simply bail out and return to earth by parachute as soon as the attack was over.
Work began at the Bachem-Werke in Waldensee in 1944 and the result was the Ba-349 Natter, which translates as Adder or Viper. This was destined to become one of the oddities of World War II. It was intended to bring down the formations of Allied bombers that were relentlessly pounding German factories and cities in the latter years of the war. The Ba-349 followed a simple design that even semi-skilled workers could construct in less than 1,000 hours. The control surfaces were confined to the tail fins, making it easy to fly and simple to manufacture. It was powered by a Walter 109-509A rocket motor generating 3,700lb (1,700kg) of thrust and was equipped with 4 Schmidding 109–533 solid-fuel booster rockets fixed to the fuselage to assist the launch. Fully laden, the Natter weighed 4,800lb (2,177kg) of which 1,400lb (635kg) was fuel. The plane measured 21ft 3in (6.5m) in overall length and was fitted with two sets of 12 solid-fuel 2.84in (73mm) rockets to be fired in a single volley.
Flight testing of unpowered prototypes began in November 1944 at Neuburg an der Donau. The first was towed up to nearly 10,000ft (3,000m) by a Heinkel He-111 bomber and the test pilot, Erich Klöckner, reported that it handled well. In December 1944 vertical take-off tests were started at Truppenübungsplatz near Lager Heuberg yet the first manned flight in March 1945 soon ran into difficulties and the pilot, Lothar Sieber, was killed when his parachute failed to open. Problems were experienced from the start; even with the rocket boosters the velocity of the Natter when launched was too low for the control fins to work effectively, so steel vanes were fitted to deflect the rocket exhaust. They were prone to melting in the heat, so they were filled with water; although the water soon boiled away and the vanes were destroyed by the temperature of the rocket fame, the Natter had — by that time — gained enough speed to be conventionally controlled.
As the war was ending, the factory was closed down and a Dutch designer named Botheder was dispatched to take four of the Natters to a new base. Botheder was reported to have a ski chalet, the Einen Achalpe, in the nearby mountains and it was apparently agreed that this is where the teams would rendezvous after the troubles were over. In the event, he was intercepted en route to this eagle’s lair by advancing American forces in May 1945 and the truth was out. Botheder explained that the remaining staff members were a test pilot named Zeubert, who had successfully flown an unpowered gliding version of the prototype, an engineer called Granzow, who was in charge of the rocket motor, and a coordinator who kept a watchful eye on the proceedings. This man’s name was Schaller, and Botheder said he was convinced he was a Nazi party member put there to report back, secretly, on everything that was happening.
In total, 36 Natters were constructed during the war. Of these, 18 were used as test vehicles and two were destroyed in crashes. Ten were destroyed at the end of the war. One Natter was taken by the British, and another by the Soviet Army. Four of the surviving Natter rocket planes were taken back to the United States. One of these was test-fired, unmanned, from the Muroc Army Air Base in 1946. It was the first manned surface-to-air interceptor. Only three of the Natters have survived. There is a Ba-349A at the Deutsches Museum in Munich, now painted in the markings of one of the unmanned test aircraft. A second Natter is in the collections of the National Air & Space Museum in Washington DC. There is also a Ba-349A on show at the Planes of Fame Museum in Chino, California; this one, however, is only a wooden copy. In Japan during the last days of the Pacific War, the Mizuno aircraft company began constructing an aircraft that was based on the concept of the Natter. The Mizuno Shinryu interceptor rocket plane was the result. It would have been equipped with rockets fired from under its wings and could also have been fitted with a warhead in the nose, to be used for a suicide attack. Development was still underway at the end of the war.
And this provides us with a fascinating thought. The rate at which these new designs were realized seems extraordinary in a modern world, hide-bound by administration, bureaucracy, health and safety directives and the need to comply with regulations. From the viewpoint of wartime Germany, work began too late. Had the Axis powers begun work on their secret weapons earlier, many of these extraordinary innovations would have been proved a success and the course of the war might have turned out very differently.
Many of the secretly designed planes of World War II came from more conventional sources. For example, the Heinkel He-111 had been developed in peacetime in direct defiance of the Treaty of Versailles. Although claimed to be a commercial transport aircraft it had been covertly designed for easy conversion to military purposes. It became the Luftwaffe’s standard twin-engined bomber and was produced in scores of different variations. Typical of the type were planes with a wingspan of 82ft (25m) and length of 52ft 6in (16m), with an operating speed of 280mph (450km/h). In 1940, 750 of the planes were under construction; the number doubled during 1942, with the result that this bomber was produced in greater numbers than any other German plane during the early years of the war. It took part in the Battle of Britain, but the superiority of the British fighters proved that its time had passed. It had poor manoeuvrability, limited operating speed, and its armaments were inferior. However, it could often remain flying even when badly damaged and so was eventually employed on many fronts during the war. As well as serving as a bomber it was useful as a transport aircraft on the Eastern, Western, Mediterranean, Middle East and North African Fronts, and was successfully used to drop torpedoes in the North Atlantic campaign. As the war ended, the He-111 re-emerged in a different guise, ensuring the design remained in use for many years. It was produced in Spain under licence by Construcciones Aeronáuticas SA, and the first of these planes flew before the war ended in May 1945. After the war, since it was no longer possible for the manufacturers to obtain the Junkers engines, they installed the Rolls-Royce Merlin 500 instead. Over 170 Merlin engines were ordered in 1953 alone. A nine-passenger transport aircraft, the 2.111T8, was to follow. Many of these planes found a use in movies about World War II, repainted to look like the original Heinkels. The Spanish planes continued in daily use until they were finally withdrawn from service in 1973.
The strangest version of the He-111 was the top-secret heavy-duty version designed to tow gliders filled with tanks, artillery and troops. It was manufactured as a pair of conjoined He-111 aircraft with a common wing upon which a fifth engine was mounted. The entire wingspan was some 125ft (38m) and the pilot flew the plane from a cockpit in the left-hand fuselage using identical, linked control levers. Towing a glider of over 35 tons, this twin aircraft was said to have flown to 30,000ft (9,100m) in 1942. The large numbers of these vast tow-trucks that would have been necessary for large-scale invasions were never produced. Certainly the handling and aerodynamics of this bastard giant would have been intimidating at the very least.