The Bachem Ba 349 Natter (English: Colubrid, grass-snake[Note 1]) is a World War II German point-defence rocket-powered interceptor, which was to be used in a very similar way to a manned surface-to-air missile.

The primary role of the relatively untrained pilot was to aim the aircraft at its target bomber and fire its armament of rockets.

Surface-to-air missiles appeared to be a promising approach to counter the Allied strategic bombing offensive; a variety of projects were started, but invariably problems with the guidance and homing systems prevented any of these from attaining operational status.

Submissions for a simple target defence interceptor were requested by the Luftwaffe in early 1944 under the umbrella of the Jägernotprogramm, literally "Emergency Fighter Program".

[2][3] A number of simple designs were proposed, including the Heinkel P.1077 Julia, in which the pilot lay prone (on his stomach), to reduce the frontal area.

The initial plan was to launch the aircraft vertically, but this concept was later changed to a conventional horizontal take-off from a tricycle-wheeled trolley, similar to that used by the first eight prototypes of the Arado Ar 234 jet reconnaissance bomber.

[4] The Natter was first conceived by Dr Erich Bachem in August 1944, after witnessing an American bombing raid on a major German city.

[6] It was built using glued and nailed wooden parts with an armour-plated bulkhead and bulletproof glass windshield at the front of the cockpit.

By the time the aircraft left the tower it was hoped that it would have achieved sufficient speed to allow its aerodynamic surfaces to provide stable flight.

[8][9] Under operational conditions, once the Natter had left the launcher, it would be guided to the proximity of the Allied bombers by an autopilot with the possibility of an added beam guidance similar to that used in some V-2 rocket launches.

Following its one-time attack with its rockets, the pilot would dive his Natter, now effectively a glider, to an altitude of around 3,000 m (9,800 ft), flatten out, release the nose of the aircraft and a small braking parachute from the rear fuselage.

Bachem stated clearly in the initial proposal that the Natter was not a suicide weapon and much effort went into designing safety features for the pilot.

[10] However, owing to the potential dangers for the pilot inherent in the operation of this precarious aircraft, the Natter is sometimes listed as a suicide craft.

In the middle of September 1944, the Technical Office of the Waffen-SS made an order for Bachem to develop and manufacture the Natter at his Waldsee factory.

As the nose section separated, it was intended to briefly pull on two cables that released a small ribbon parachute stored on the starboard side of the rear fuselage.

[citation needed] Wind tunnel testing on a wooden model, scaled to 40% of full size, was performed at the Deutsche Versuchsanstalt für Luftfahrt (DVL), the Institute for Aerodynamics at Berlin-Adlershof in September 1944 at speeds up to 504 kilometres per hour (313 mph).

[21] In March the Bachem-Werk simply received a statement that satisfactory flying qualities should be expected with speeds up to 1,100 kilometres per hour (680 mph).

[24] The vertical take-off trials were conducted on high ground called the Ochsenkopf at the Truppenübungsplatz (military training area) Heuberg near Stetten am kalten Markt, Württemberg.

The remainder of the fuselage came down under its two large salvage parachutes, but when it hit the ground the Walter liquid-propellant rocket engine's residual hypergolic propellants (T-Stoff oxidizer and C-Stoff fuel) exploded and the machine was destroyed.

[29] A hard wire intercom appears to have been provided between Sieber and the engineers in the launch bunker using a system similar to that used in the manned glider flights.

The Walter liquid-fueled rocket engine built up to full thrust and Sieber pushed the button to ignite the four solid boosters.

It is estimated the Natter reached 1,500 m (4,900 ft), at which point it nose-dived and hit the ground with great force about 32 seconds later, some kilometres from the launch site.

[33] The accident reinforced Bachem's long held belief that the take-off and flight in the vicinity of the target bombers should be fully automated.

Before the introduction of the autopilot in the test programme, the control column would have a temporary locking device on it, which would allow the machine to ascend vertically to at least 1,000 m (3,300 ft) and then be removed by the pilot.

[35] Sieber had become the first person to take off vertically from the ground under pure rocket power, 16 years before Yuri Gagarin's Vostok 1 pioneering, peacetime orbital flight.

[25] Up to April 1945, 17 aircraft had been used in unmanned trials comprising five gliders, all slung under an He 111 in the Mistelschlepp configuration prior to launch, and 12 VTO examples.

[40] In early February 1945, the positions of the centre of gravity for the A1 operational machine during its flight profile were giving the RLM and the SS cause for concern.

The centre of gravity problem was solved initially by the addition of one-metre-square auxiliary tailfins that were released simultaneously with the jettisoning of the boosters.

Around the end of February and the beginning of March the Organisation Todt was in action, constructing each set of the trios of concrete foundations (or "footings") for the launch towers.

There are several static reproductions of Natters around the world, for example at the Planes of Fame Air Museum, Chino, California and Fantasy of Flight, Polk City, Florida, US.