This rocket-powered vertical take-off interceptor, called the Natter, convinced the Allies that the Nazis broke the laws of physics towards the end of World War II.
Imagine a tiny Space Shuttle, launched vertically from southern Germany, with four solid-fuelled booster rockets and a main liquid-fuelled sustainer motor powering the craft upwards at 2.5g. Ten seconds later, the boosters fall away, their propellant exhausted. The machine is now flying at 550 mph and has reached 4,000 feet. Now on rocket motor power alone, the steady reduction in fuel mass increases its velocity. It soon climbs at 37,000 feet per minute, comparable with the Space Shuttle’s figures for the first sixty seconds. Reaching the level of the Allied bombers, the pilot disengages his autopilot and launches a salvo of unguided air-to-air rockets at the nearest aircraft. Fuel and ammunition now exhausted, the pilot pulls a lever, his craft breaks apart, and is parachuted back to Earth in sections for repair and re-use. He is catapulted into mid-air and deploys his own ‘chute safely.
With 36 built in early 1945, this secret weapon existed. Its official designation was the Bachem Ba 349 Natter (“Adder”), and only the arrival of Allied tanks prevented an initial deployment against American bombers. It was also cited as being behind the “Foo Fighter” sightings that had puzzled Allied Air Intelligence over the winter of 1944/45.
Gotterdammerung: The Rise of the Natter
In 1944, Germany was pounded by American bombers during the day and the British by night, forcing aircraft production into dispersed workshops. Waldwerke (“forest factories”) were created near bombed plants and finished machines being towed onto Autobahn airstrips. Burrowed into a hill, an underground facility building Messerschmitt Me 262 jet fighters had its summit leveled to provide a runway. Completed jets were transported to the top by a hillside elevator. Synthetic oil plants supplying the armed forces could not be dispersed, however, nor could dams or bridges. How could the Luftwaffe defend these when its fighter pilots were being shot down in droves, leaving only a few Experten (“aces”) and hundreds of enthusiastic yet inexperienced young airmen?
The advent of rocket and jet-propelled fighters such as the Me 163 Komet and Me 262 in July 1944 did not tip the balance Germany’s way. They suffered from numerous problems. The Me 262’s Junkers 109-004B turbojets needed an overhaul after 10 hours of use, while clumsy throttle control caused engine fires. The Komet was dangerous to operate, requiring careful handling. One of two highly volatile fuels used by its Walter rocket motor spontaneously combusted on contact with organic substances. The aircraft took off using a jettisonable wheeled dolly and climbed at 12,000 feet per minute. Seven minutes of fuel was carried, allowing two firing passes before the Komet turned into the world’s fastest glider. It landed on a skid and occasionally overturned, allowing fuel dregs to escape and explode. Compared to the Allied bombers they shot down, more Komets were lost to accidents.
The Luftwaffe’s piston-engined fighters were outnumbered and outclassed by USAAF P-51 Mustangs and P-47 Thunderbolts. The Nazis needed an easy-to-fly interceptor that could be built cheaply, quickly, and in large numbers. It needed to be both expendable and reusable depending on need. The Reichsluftministerium (RLM, or “State Air Ministry”) invited companies to submit tenders. Four designs were submitted, the Heinkel P.1077 Julia, Junkers EF.127 Walli, Messerschmitt Me P.1104 and Bachem-Werke BP.20.
The Natter, A Re-usable Rocket Interceptor
Erich Bachem had helped design the Fieseler Fi 156 Storch (“Stork”) liaison aircraft and worked on a vertical take-off rocket-powered interceptor project, the Fi 166. The latter was conceptualized by Wernher von Braun of V-2 rocket fame.
Bachem established his own company in 1942 at Bad Waldsee in Baden-Württemberg, Bachem-Werk supplying parts for high-performance types, including the Heinkel He 162Volksjäger (“People’s Fighter”), a single-engine jet aircraft initially intended to be flown by Hitler Youthwith minimal instruction.
Bachem’s first attempt was a “ram rocket” with a concrete nose designed to smash through fuselages or wings. It was a cigar-shaped projectile with four stubby wings and tail fins. The pilot would lie prone behind the nose. Details were submitted to the RLM in August 1944 to obtain an official sanction. However, patronage from high-ranking officials was vital. If a VIP disliked a designer or his project, the chances of development were slim. Obtaining the blessing of important Party members guaranteed success, even if the RLM weren’t keen. The latter, unimpressed by Bachem’s ignorance of formal tendering processes and vague notions regarding the weapon’s deployment, rejected his concept.
Undeterred, Bachem altered his design to make it more appealing to the RLM. By late September 1944, Bachem’s BP.20 design was finalized. A standardized cockpit with a seated pilot was now included. Prone pilots, effectively standing during launch, could withstand less g-force before becoming unconscious. The concrete nose was also discarded in favor of air-to-air rockets. The BP.20 involved three separate sections. First was the cockpit, nose, and weapons system. Next came the mid-section, including the wings, fuel tanks, and forward section of the Walter rocket motor. The rear fuselage section comprised the fuel tanks, tailplane, and most of the powerplant.
Bachem’s search for an influential patron paid off when Reichsführer-SS Heinrich Himmler backed his project. Himmler had assumed command of the Army’s armament department after the July 1944 Bomb Plot and was impressed by Bachem’s design. In September 1944, he designated it as an SS project, ordering its development and manufacture. Once Himmler had endorsed the BP.20, the RLM could not block it. Lack of skilled labor was a problem. Himmler offered concentration camp inmates, but the designer refused, requesting trained mechanics, engineers, and craftsmen. One hundred twenty technicians, injured in combat, were assigned to Bachem-Werk and designated SS-Sonderkommando Waldsee. Female forced laborers helped construct BP.20 fuselages, sanding down surfaces and assembling cockpit canopies.
The BP.20 was a frugal design, as it was to be built quickly, cheaply, and using the least amount of strategic materials. As Volksjäger production monopolized supplies of high-quality wood, Bachem used laminates assembled from inferior stocks. Plywood sheeting was used to cover the 19-foot long fuselage and 13 foot wide wings. The RLM ordered that thick cardboard would replace the plywood when the aircraftwas eventually put into mass production. For testing and operational aircraft, single solid-fuelled booster rockets were fitted on each side of the rear fuselage, where the Walter HWK 109-509A liquid-fuelled rocket motor was installed.
Called the Natter, the aircraft separated into sections that parachuted down to Earth after each mission. A system of pintles, guide pins, and locking plates joined the nose and fuselage mid-sections. To exit the craft, the pilot operated a lever, releasing rods keeping the locking plates attached to the pintles. Aerodynamic forces then forced the sections apart. The remaining fuselage areas were joined together by clamp bolts, separated by the same control rods. A parachute was attached to the forward end of the Walter rocket motor, allowing the tail section to be retrieved and re-used. The boosters were expendable.
Construction of the first prototype began immediately after Himmler’s go-ahead, and it was completed on 4th October 1944. Several test flights occurred over the next several months with some success. However, aircraft procurement officials became disillusioned with the design as several issues with the Natter began to present themselves. Chiefly, the aircraft had trouble disassembling mid-flight as promised. With significant milestones yet to be reached, the military began supporting more conventional projects such as the He P.1077 Julia.
Despite SS backing, vital supplies dried up. The SS-Sonderkommando rectified matters by seizing materials from local farms. In December 1944, SS-OberstgruppenführerHans Kammler took control of the Natter project. Kammler, who had a doctorate in engineering, was utterly ruthless. He had access to concentration camp prisoners, using thousands to construct the Mittlewerk underground complex near Nordhausen, where V-2 rockets and V-1 flying bomb parts were built.
An army training area south of Stuttgart was chosen for take-off trials, where a 65 foot-tall steel-framed launch tower was constructed. M21, the first Natter assigned to take-off trials, arrived in mid-December 1944, and not two but four Schmidding boosters were fastened onto its rear fuselage. The Walter sustainer motors were not yet available, so the first unmanned launches only used booster rockets. Explosive bolts fitted to a restraining device failed, and M21 was destroyed when the boosters ignited. M16 was launched on the 22nd. One booster partially fired, yet the machine left the tower safely, with forces estimated at 2.25g. M17 was ready on the 29th. Painted yellow with a black “sunburst” pattern on the wings for telemetry recording purposes, its tailplane carried a “finder and reward” notice to ensure its safe return. Again, itwas launched successfully, but the salvage parachutes failed. Bad weather and delays in supplying boosters halted testing until mid-February.
Further launches that month highlighted ongoing issues with the parachutes. Bachem was also under pressure to provide manned Natters for operations but had other problems to sort out before complying. One major headache was the Walter liquid-fuelled rocket installation. The Natter could not reach operational altitude using the Schmidding boosters alone.
M22 was the first Natter to be fitted with its full complement of rocket motors. As installed in the Me 163 Komet interceptor, the Walter unit used two extremely volatile fuels, C-Stoff and T-Stoff. C-Stoff was powered by hydrazine hydrate, methyl alcohol, and water. T-Stoff used hydrogen peroxide in concentrations 25 times greater than bleach. It spontaneously combusted on contact with organic material such as dust or dirt – and humans. Launched on 25th February 1945, all five of M22’s rockets performed perfectly. The nose separated flawlessly, the dummy pilot fell away, and the parachutes for the rear sections worked perfectly. However, residual fuel in the Walter unit ignited, and the rear fuselage burnt out. Despite Bachem’s pleas for more tests, Kammler ordered him to conduct a manned flight immediately.
The situation at the front was now critical, and the Nazis were losing the war.
Lothar Sieber, a pilot demoted due to drinking on duty, was chosen to fly the first manned Natter flight. He had served with Kampgeschwader 200, a secretive unit tasked with dropping agents behind enemy lines, and earned commendations for operations on the Ostfront. Sieber joined Bachem-Werk in December 1944, probably at the behest of Otto Skorzeny, head of the SS-Jagdverbände (special forces). Sieber’s flight was scheduled for the 1st of March 1945 and involved Natter M23. With a loud roar, it cleared the tower, rolling inverted at 330 feet. The cockpit canopy then detached, taking the pilot’s headrest with it. Sieber’s head was flung backward under the sudden g force, and he was either rendered unconscious or sustained a broken neck. Observers lost sight of M23 as it flew into the clouds. The wreckage was eventually discovered two miles away. Sieber made the history books by becoming the first person to be launched vertically from the ground by rocket power, even though they could only find a bit of his skull, half of his left arm and leg. In the late nineties, excavations of the Natter’s crash site discovered that his body had never been ejected.
Despite this failure, Kammler demanded further manned launches. Unfortunately, vital materials, including cement blocks simulating the weight of the weapons system, failed to arrive. Plans were created for the operational deployment of ten machines under Operation Krokus. The war was nearly over, but the SS still wanted Krokus implemented.
Fitted with two guide runners, a simple pole launcher was assembled in early March 1945 to test four Ba 349A-1 production aircraft. The first (unmanned) machine launched in early April. Work on erecting ten pole launchers near Kirchheim unter Teck, near the Stuttgart to Munich autobahn, finished in late March. Eight pilots received instruction on Natters, and ten production aircraft were built at Waldsee for Krokus. They were armed with 24 Henschel Hs 297 Föhn unguided air-to-air rockets installed in a nose launcher. The date chosen for Krokus was April 20th, 1945.
The plans were soon thrown into disarray. On April 3rd, Kammler ordered V-weapons research personnel to retreat to Oberammergau, southwest of Munich. Twelve days later, several Bachem-Werk personnel, with four Natters, departed for Austria. On April 21st, the intended date for Krokus, the American 10th Armored Division captured the pole launchers near Kirchheim unter Teck, forcing personnel to flee to Waldsee and destroy the remaining Natters there. Ten days later, the first group reached Sankt Leonard im Pitztal, near Innsbruck. A second group with two Natters burned them at Schlatt in Austria, just before the Americans arrived. US Army photographers took pictures of three Natters sitting on trailers at Sankt Leonard shortly after their capture. The first group believed that the Americans would let them develop the Natter for the Allies, suggesting it could be used as a ship-borne interceptor against Japanese air attacks.
Although not transported with captured Luftwaffe aircraft sent to America under Operation Lusty, two Natters arrived at Freeman Field in Indiana during July 1945. One of these appeared at Santa Monica Airport, California, in August. Another featured in the November 1945 issue of Aviation Week, pictured at Freeman Field wearing spurious German insignia. These likely were two of those captured in Austria. One was transported to Park Ridge, Illinois, for storage. It was passed to the Smithsonian Institution, ending up at the Paul E. Garber facility at Suitland, Maryland, where it resides today in an unrestored condition. The fate of the other Natter is unknown. Rumors persist that it was used in a radio-controlled launch from Muroc Army Airfield (now Edwards AFB), California. Erich Bachem created furniture and caravans after the war, a far cry from designing the fastest climbing interceptor of WW2.
Re-Inventing the Wheel?
With more testing time, access to better materials, and skilled labor, the Natter may have been operational much earlier. These rocket-powered interceptors could have wreaked havoc with bomber formations, being almost impossible to catch as they rose from sites across Germany. Firing rockets at a group of B-17s would have brought down one or more aircraft, and a dozen Natters could have overwhelmed a single bomber squadron before escorting fighters intervened. The Americans would have been under pressure to destroy the launching poles, which could have been concealed when not required and erected just hours before needed.
Shortly after the end of the war, the Natter was cited as an explanation for the “Foo Fighters” that had puzzled Allied intelligence officials. According to one American newspaper in August 1944, they were “tiny jet-propelled craft that were ‘buttoned’ to the base of steel poles and shot vertically into the air at the tremendous speed of rockets.” German scientists were questioned, suggesting that the Natter may have been responsible. This was way off the mark.
In April of 1981, Space Shuttle STS-1 was launched. In addition to the Shuttle’s three Rocketdyne liquid-fuelled engines, two Thiokol Solid Rocket Boosters assisted in the initial launch phase, being jettisoned at an altitude of 146,000 feet. Although NASA did not use Bachem’sdesign in their Shuttle launch profile, one can’t help thinking that they certainly tipped their hat in the direction of his interceptor. Those marveling at the awe-inspiring yet dangerous launch were probably unaware of the Natter and its potentially deadly take-off. Another similarity was that the Shuttle was designed to return to Earth for re-use, and this system of recycling craft and propulsion units continues via SpaceX’s Falcon 9 and Starship.
The Natter may have been one of WW2’s little-known secret weapons, but its concept lives on today in the latest generation of spacecraft. A relatively unknown Luftwaffe pilot was the first to be blasted skyward in a vertically-launched rocket-powered craft, but he would not be the last. The next time you see one of Elon Musk’s Starships being launched, remember that reusable rocket-powered craft flew in 1945!
Follow and connect with author Graeme Rendall on Twitter:@Borders750