Introduction:

In a war filled with strange aircraft, the Bachem Natter was arguably the strangest of all. It was a rocket-propelled semi-expendable fighter-interceptor, intended to take off vertically, like a V-2 missile, attack an American bomber formation with a nose-cone full of high-explosive rockets, and then to be abandoned by the pilot, with part of the aircraft jettisoned for re-use.

By the spring of 1944 it had become clear to the Luftwaffe High Command that serious measures would have to be taken if the increasing waves of Allied bombers penetrating the Reich were to be countered. The Me 163 Komet was ineffective against the American B-17 ‘combat box’ formations, and the Me 262 Schwalbe was not yet being used in its true role as a fighter. As a result, several unusual schemes were looked into for a new ‘point-defense’ plan designed to simplify German air defence.

The basic idea behind point-defence was as follows: Germany would be divided up into geographical ‘boxes’ or parcels of land. Each box would contain its own specifically assigned interceptors, and as the Allied bombers passed overhead these interceptors would rise up like a swarm of wasps to attack them. As the bombers flew on, so they would meet one such attack after another, passing from box to box. The bomber’s return home would meet equally stiff resistance as the fighters would have been refuelled and rearmed and could be waiting for their return.

In Planning:

Essentially, a new kind of aircraft was needed: one that would be cheap both to build and to operate, that would be robust and reusable, and if possible would have the speed to outrun the Allied fighter escorts. If the all-up weight were kept low, then a short operating range and endurance would have to be accepted, but given the box system this wouldn’t be a problem provided that the aircraft had a short turn-around time.

Various manufacturers were invited to put proposals forward later that year, and among them Diplomeur Ingenieur Erich Bachem made his first appearance with his submission of the BP 20 ‘Natter’. He was in competition with the Heinkel P.1104 ‘Julia’, the Junkers EF 127 ‘Walli’ and Messerschmitt’s Project P.1104.

Heinkel won the contract. Bachem had submitted his proposal through influential but unofficial channels offered by his close associate Hans Jordanoff, and as Technical Director of the Fieseler-Werke, builders of the V-1 flying bomb, he also had close ties with Peenemunde. But his attempt to get in through the back door, as it were, did not succeed due to other considerations. Heinkel was a preferred and established aircraft manufacturer and its Julia project had been in development since August so it was actually granted the point-defence commission on 8th September. The company won because Julia was easy and cheap to build and had low running costs. In addition, Heinkel already had its own dedicated woodworking shop in Vienna, which could be geared up to build the Julia very quickly. The Air Ministry could not have hoped for a more suitable contender.

As for Messerschmitt’s offering, it seams to have been an unusually half-hearted affair which never left the drawing board and was dropped as the company concentrated on the other pressures that the deteriorating situation in Germany was placing on all industry.

Although Heinkel duly placed the work with its woodworking plant at Vienna which, they felt, would be far enough away to be relatively safe from Allied raids unfortunately for the project, the woodworking plant was unexpectedly bombed by the Allies later in the autumn.

Undeterred at having lost the competition to Heinkel, Erich Bachem used his contacts and credentials to secure an interview with Himmler, who showed an immediate interest in his project, seeing it as a point-scoring exercise for the SS over the Luftwaffe and the regular army. Within twenty-four hours the Natter proposal was referred back to the Air Ministry for re-evaluation.

Bachem had designed his fighter as a vertical-launch rocket-propelled, semi-expendable interceptor. The idea was neither unique nor new; Blohm und Voss had adopted a similar approach with their Bv40 ‘glide-fighter’. But where the Natter triumphed over its rivals was in its simple construction and its use of strategically unimportant materials. It was also versatile: its innovative launch rails could be fitted to a warship if necessary, endowing the remaining fleet with an aerial-defence capability hitherto denied the ships, as the Kriegsmarine lacked aircraft carriers. It could be built by unskilled and semi-skilled labour, with individual components assembled in any number of small carpentry shops dotted around the Black Forest region, and brought together as completed sub-assemblies at the Bachem finishing plant. This method of construction anticipated the system advocated as best practice by many manufacturers today.

The inventor had obtained a modest undamaged factory at Waldsee, about forty kilometres from Lake Constance, which housed a small design office within its walls. He collected technicians from wherever he could find them, and a rocket expert from the Walter Werke, and begun development in earnest in August 1944 through the newly formed Bachem Company, just in time for the competition already mentioned. By the autumn, having bounced back, Bachem had over 60 skilled assembly workers who were framed out to various local-skilled sub-contractors working for the project. Because of Himmler’s patronage, the enterprise was taken into the Emergency Fighter Programme from September 1944 and received the official designation Ba 349, along with an order for fifteen prototypes.

As originally envisaged, the Natter, which was not designed with a landing capability, was to mount a two-stage attack. In phase one it would be blasted vertically off the ground, on autopilot. There, after climbing almost vertically on an internal rocket the pilot, assuming manual control when positioned above the approaching bombers, would place the aircraft in a shallow dive. The Natter would then jettison the nosecone to expose the battery of rockets. Nearing the bombers, the pilot would single one out and fire his rockets. In phase two, having fired these unguided rockets, the pilot, using his remaining kinetic energy, would climb higher than the bombers and swoop back down for a ramming attack. Just before impact he was to trigger a mechanism to separate his seat (or front fuselage) from the rear portion with rocket motor.

Tests showed however, that no such simple ejection system could be incorporated, and the essence of the Natter was simplicity so this was eventually abandoned. Phase two was then abandoned, and the plane was redesigned. Now, the aircraft was flown clear of the battle zone before the pilot was to bail out. The entire nosecone was to be jettisoned by uncoupling the control column, moving it forward to release the safety catches, and then releasing mechanical catches to separate the nose from the rest of the fuselage. The pilot was effectively ejected by the deceleration of the rear section as it streamed a braking and recovery parachute. The rear fuselage, containing the valuable rocket engine, would parachute to the ground for recovery and reuse. Other detailed design improvements continued with wind-tunnel testing, which revealed little to desire in the Natter’s aerodynamics, until an overall final version was arrived at. In contrast to the Horten brothers, Bachem had access to every facility, even though the Horten’s Go 229 also fell within the Emergency Fighter programme; the brothers were denied such basics as wind-tunnel time, in favour of the Bachem design.

Launching:

The launch tower was first designed as a steel latticework structure like a big piece of Meccano; it stood a little over twenty-three metres high. Towards the end of the war, as steel became ever scarcer, this was replaced with a simple nine-metre telegraph pole with a pair of shortened launch rails bolted to it. Common to both designs was the need for a solid concrete foundation into which the gantry could be secured, though the telegraph pole version could be quickly dismantled and removed from a mounting set into such a base. With dozens of these small foundations scattered around the launch area, ground crews could move their gantries from one to another swiftly, and Allied pilots would be lucky to trace them. We are familiar with the concept used by modern rockets such as the ‘Ariane’’ series used by the European Space Agency. The rocket is freestanding on its booster nozzles, needing an adjacent gantry only to give service access. Any in-flight course corrections can be made by adjusting the angles of the nozzles to redirect the thrust.