Initial designs were not promising. The Heinkel P1077 Julia, the most viable of all proposed designs, involved an awkward vertical take-off and required the pilot to lie on his stomach while flying. Unimpressed, German engineer Erich Bachem decided to lend a hand.
For some time, he had been developing his BP-20 Natter missile while working at German aircraft manufacturer Fieseler. Built using glued and nailed wooden parts with an armour-plate bulkhead and bulletproof glass windshield at the front of the cockpit, the missile would be launched by being slid up a 20m-high vertical launch tower. Once airborne, the missile’s autopilot would guide it to within close proximity of an Allied bomber, at which point the pilot would take over, aim, and then fire the armament.
But this was not a kamikaze aircraft. Having reached the airspace above the Allied bomber from which to fire the weapon, the Natter – whose Walter motor would by then be out of propellants – would glide down to an altitude of 3,000m. Here, the pilot would straighten the craft out and release the nose, at which point a small breaking parachute would be released from the fuselage, ejecting the pilot through the front.
The plan was not fool-proof, but it was enough to catch the attention of Heinrich Himmler. In September 1944, Bachem was ordered to develop and manufacture his Natter at the Waldsee factory. His already sparing design was subject to a series of strict reforms to try and bring down the cost of the missile. Once these were completed, it was time for the all-important testing process.
Towed by a Heinkel He 111 bomber at 3,000m and piloted by Erich Klöckner, the first Natter prototype – known as the M1 – showed great potential in glider mode. The next step was to test the Natter’s capability for vertical take-off (VTO).
It was now time for the manned test. The auto-pilot facility for the first part of the flight had still not been installed, so the whole flight would, in this case, have to be controlled by a live pilot. Bachem expressed his concerns about this, worried that the testing was being cut short.
On 1 March, Lothar Sieber, a young Luftwaffe test pilot, stepped forward to pilot the Natter. From its launch tower, it was successfully thrust straight up into the air amid a cloud of steam and smoke. At roughly 150m altitude, however, it was seen to pitch back, adopting an inverted curve flight-path. The cockpit canopy flew off unexpectedly at about 500m and still the Natter climbed, now at a dangerously steep angle, eventually disappearing into low-flying cloud.
At an estimated 1,500m, the Walter engine stalled and the Natter’s momentum was lost. It nose-dived at tremendous speed, smashing into the ground after only 32 seconds in the air. Sieber’s tragic death strengthened Bachem’s belief that both the take-off and the flight towards the target bomber should have been fully automated.
The Natter never saw action, and by the time Bachem had a prototype close to operational, the Waldsee factory had been captured by French forces. Lothar Sieber, despite the 32-second catastrophe resulting in his untimely death, became the first man to take off vertically from the ground under pure rocket power.