Single seat, single engine, rocket powered interceptor, WW2

Dr. Erich Bachem's Ba 349 Natter (Viper) was the world's first, manned, vertical-take-off interceptor. The aircraft was an imaginative solution to a desperate problem, but World War II ended before the weapon saw combat. Dr. Werner von Braun first proposed the concept in 1939, but the German Air Ministry (RLM) rejected it as "unnecessary and unworkable." Bachem, an engineer with the Fieseler works, thought the idea had merit. He tried but failed to generate interest in several different proposals for a rocket interceptor.

During spring 1944, the Allied bombing offensive began taking a serious toll on the German war machine. None of the conventional methods employed by the Luftwaffe to intercept the bombers seemed to work, so the service began to explore unconventional means. The RLM Technical Office issued requirements for an inexpensive fighter made of non-essential materials that could defend important targets. Messerschmitt, Junkers, Heinkel and Bachem submitted proposals, but RLM officials remained unenthusiastic about Bachem's design. They chose a more conventional offering from Heinkel.

Bachem refused to give up. He sought the support of Reichsführer Heinrich Himmler, head of the SS. Himmler approved the idea and signed an order to build 150 Natters using SS funds. The RLM, unwilling to lose control, placed its own order for 50 aircraft and designated the design Ba 349.

The aircraft was simple and could be built by semi-skilled labor in about 1,000 man-hours. The wings were plain wooden slabs with no ailerons or flaps. The cruciform tail had four fins with control surfaces that, when deflected, managed pitch, yaw, and roll. These were aided by guide vanes in the rocket exhaust. The main engine was a Walter 109-509A — the same used in the Messerschmitt Me 163 Komet. It used two volatile fuels: T-Stoff (hydrogen peroxide solution) and C-Stoff (hydrazine hydrate mixture), which ignited on contact.

The Walter motor alone generated about 1,700 kg of thrust, but the loaded aircraft weighed more than 1,800 kg. Bachem added four Schmidding 109-533 solid-fuel boosters, each giving 500 kg thrust. Total launch thrust was about 3,700 kg, providing a 1.6:1 thrust-to-weight ratio and acceptable climb rate.

A 24-meter tower launched the Natter vertically. Guide rails held the fins and wings in position. The controls were locked during the initial 10 seconds. When boosters burned out, explosive bolts jettisoned them, and the autopilot took over via ground radio. The pilot could take control at any time.

Bachem estimated a maximum climb rate of 11,563 meters per minute. U.S. bombers flew at 6,250–9,375 meters. Once the Natter reached this altitude, the pilot jettisoned the nose cone and fired 24 unguided Henschel Hs 217 Föhn rockets in a salvo.

With fuel nearly spent, descent began. At about 1,400 meters, the pilot ejected the nose section, triggering a fuselage parachute that flung him from his seat. He then deployed his personal parachute. The airframe was lost, but the Walter motor could be recovered.

Bachem's facility in Waldsee began testing in late 1944. A motorless glider version was dropped from a Heinkel He 111. The pilot reported good control and a successful escape. A vertical launch with only boosters succeeded in December. Ten more test flights followed. A full launch using the Walter engine and a dummy pilot occurred on February 25, 1945 — all systems worked.

On February 28, Oberleutnant Lothar Siebert piloted the first manned vertical launch. At about 500 meters altitude, the aircraft shed its canopy and crashed. Siebert was killed. Cause unknown, possibly a canopy malfunction. Still, other pilots volunteered. Three more flights took place in March.

A battery of ten Natters was prepared near Kircheim, but no U.S. bombers came within range. The site was captured by U.S. forces; all aircraft and launchers were destroyed beforehand.

Training was impractical since the airframe was not reusable. A simple ground simulator might have been feasible, but the Natter's one-shot, unguided rocket attack was of limited effectiveness. U.S. forces could easily change flight paths. In the end, the Ba 349 was a desperate solution that failed in practice.

Two Natters survive: one in the Deutsches Museum in Munich, and the other at the National Air and Space Museum (NASM) in the U.S. Captured in 1945 and designated equipment T2-1, it was transferred to NASM in 1949.