Aggregat

The Aggregat series (From the German for "Aggregate" or "Assembly") was a set of ballistic missile designs developed in 1933–1945 by a research program of Nazi Germany's Army (Heer). Its greatest success was the A4, more commonly known as the V2.

thumb|right|Aggregat rockets compared

A1 (1933)

The A1 was the first rocket design in the Aggregat series. It was designed in 1933 by Wernher von Braun at the German Army research program at Kummersdorf headed by Colonel Dr Walter Dornberger. The A1 was the grandfather of most modern rockets. The rocket was long, in diameter, and had a takeoff weight of . The engine, designed by Arthur Rudolph, used a pressure-fed rocket propellant system burning ethanol and liquid oxygen, and produced 2.9 kN (660 lbf) of thrust for 16 seconds. The LOX tank was located within the fuel tank and insulated with a fiberglass material. The rocket was stabilized by a 3 axes gyroscope system in the nose, supplied by Kreiselgeräte GmbH. The rocket could not be rotated for stability as with a ballistic shell, as centrifugal force would force the liquid fuel to rise up along the walls of their tanks, which made feeding propellants to the combustion chamber difficult. Although the engine had been successfully test fired, the first flight attempt blew up on the launching pad on 21 December 1933, half a second after ignition. The cause was a buildup up of propellants before ignition of its engine. Since the design was thought to be unstable, no further attempts were made, and efforts moved to the A2 design. The A1 was too nose-heavy, and to compensate, the gyroscope system was moved to the middle of the A2, between the oxygen and ethanol tanks.<!---->

A2 (1934)

thumb|right|A2 rocket

Static tests and assembly were completed by 1 October 1934. Two A2s were built for a full-out test, and were named after a Wilhelm Busch cartoon, Max and Moritz. On 19 and 20 December 1934, they were launched in front of senior Army officers on Borkum island in the North Sea. They reached altitudes of .<!---->

In March 1936, Generaloberst Werner von Fritsch witnessed a static firing of an A3 engine at Kummersdorf, and was sufficiently impressed to lend his support to the rocket program. Like the earlier A1 and A2 rockets, the A3 used a pressure-fed propellant system, and the same liquid oxygen and 75% ethanol mixture as the earlier designs. It generated its for 45 seconds. It used a three-gyroscope system to deflect tungsten alloy jet vanes. The design was finished in early 1936 and further modifications that made the rocket stable at supersonic velocities were finalized later that year.

The shape of the rocket was based on the 8-mm rifle bullet, in anticipation of supersonic flight. The rocket was in length, feet in diameter, and weighed when fueled. Fins were included, for "arrow stability", structurally anchored by an antenna ring. The stabilized platform used a pitch gyro and a yaw gyro, connected to pneumatic servos, which stabilized the platform along the pitch and yaw axes. Electrical carriages on the platform acted as integrating accelerometers. These signals were mixed with those from the SG-33 system, to drive the molybdenum-tungsten jet vane control servomotors. The SG-33 was fixed to the rocket, not the stabilized platform, and used three rate gyros to sense roll, pitch and yaw deviations. Two of the jet vanes rotated in the same direction for pitch and yaw control, and in opposite directions for roll control. The guidance and control system was designed by Fritz Mueller, based on Johannes Maria Boykow's ideas, the technical director of Kreiselgeräte GmbH ("Gyro Instruments Limited"). The parachute was disabled in the third and fourth rockets launched on 8 and 11 December 1937, but these, too, experienced engine failures, though the lack of parachute drag allowed them to crash further from the launch site. They reached altitudes between , before falling into the sea.

The propellants of choice continued to be liquid oxygen, with a 75% ethanol and 25% water mixture. The water reduced the flame temperature, acted as a coolant, and reduced thermal stress. Subsequently, a plan was formed to make an attempt to capture a complete unexploded V-2 rocket and transport it to Britain. Around 20 May 1944, a relatively undamaged V-2 rocket fell on the swampy bank of the Bug River near the village of Sarnaki, and local Poles concealed it before German arrival. The rocket was then dismantled and smuggled across Poland. In late July 1944, the Polish resistance secretly transported parts of the rocket out of Poland in Operation Most III (Bridge III) for analysis by British intelligence.

Projekt Schwimmweste

In late 1943 German Labour Front (Deutsche Arbeitsfront/DAF) Director, Otto Lafferenz, proposed the idea of a towable watertight container which could hold an A4 rocket. This suggestion progressed to the design of a container of 500 tons displacement to be towed behind a U-boat. Once in firing position, the containers would be trimmed to drop their aft end to a vertical position for launch. The project was dubbed Projekt Schwimmweste (German for "Project Life Jacket") and the containers themselves referred to by the codename Prüfstand XII (German for "Test Rig XII"). Work on the containers was carried out by the Vulkanwerft, and a single example was completed by the end of the war, but never tested with a rocket launch.

===A4b/A9===<!-- This section is linked from Peenemünde -->

In anticipation of the possibility that launch sites might be forced back into the Reich itself, von Braun and his colleagues were pressured to develop a longer-range version of the A4 known alternatively as A9 and A4b, the reason for the dual designation being that the A4 series had received "national priority"; the A4b designation ensured the availability of scarce resources.

In June 1939, Kurt Patt of the Peenemünde Design Office, proposed wings for converting rocket speed and altitude into aerodynamic lift and range. As the rocket encountered thicker atmosphere on its descent phase, it would execute a pullout and enter a shallow glide, trading speed for distance. Patt also proposed the Flossengeschoss (fin projectile). Both concepts were used by Walter Dornberger when he drafted a memo for presentation to Hitler regarding the "America rocket" on 31 July 1940.

Design studies on the A9 began in 1940. In addition to its wings, the A9 would have been somewhat larger than the A4 and its engine would have produced about 30% more thrust. Following wind tunnel testing of models, the design was subsequently modified to replace the wings with fuselage strakes, as the tests showed that these provided better lift at supersonic speeds and also solved the problem of transonic shift of the center of lift.

Development was suspended in 1941, but in 1944 several V-2s were modified to an approximation of the A9 configuration under the designation A4b. It was calculated that by fitting wings, the A4's range would be extended to

A7

The A7 was a winged design that was never fully constructed. It was worked on between 1940 and 1943 at Peenemünde for the Kriegsmarine. The A7 was similar in structure to the A5, but had larger tail unit fins (1.621 m²) in order to obtain greater range in gliding flight. Two unpowered models of the A7 were dropped from aeroplanes in order to test flight stability; no powered test was ever performed. The finished rocket should have produced a takeoff thrust of and a takeoff weight of . The design had a diameter of and a length of .

A8

The A8 was a proposed "stretched" variant of the A4, to use storable rocket propellants (most likely nitric acid and kerosene). The design never reached the prototype stage, but further design work was carried out after the war by a German rocket team in France as the "Super V-2". The project was eventually cancelled, but led to the French Véronique and Diamant rocket projects. or (with booster)

|ceiling=

|altitude= (single stage flight) or (A9/A10 combination)

|filling= payload

|guidance=

|detonation=

|launch_platform=ground launch pad or A10

It was proposed to use an advanced version of the A9 to attack targets on the US mainland from launch sites in Europe, for which it would need to be launched atop a booster stage, the A10.

Design work on the A10 began in 1940, for a projected first flight to take place in 1946. The initial design was carried out by Ludwig Roth und Graupe and was completed on 29 June 1940. Hermann Oberth worked on the design during 1941, and in December 1941 Walter Thiel proposed that the A10 use an engine composed of six bundled A4 engines, which it was thought would give a total thrust of .

Work on the A10 was resumed in late 1944 under the Projekt Amerika codename, and the A10's design was amended to incorporate a cluster of six A4 combustion chambers feeding into a single expansion nozzle. This was later altered to a large single chamber and single nozzle. Test stands were constructed at Peenemunde for firings of the thrust motor.

It was considered that existing guidance systems would not be accurate enough over a distance of , and it was decided to make the A9 piloted. The pilot was to be guided on his terminal glide towards the target by radio beacons on U-boats and by automatic weather stations landed in Greenland and Labrador.

The final design of the A10 booster was approximately in height. Powered by a thrust rocket burning diesel oil and nitric acid, during its 50-second burn it would have propelled its A9 second stage to a speed of about . The A9 would then ignite and accelerate an additional , reaching a speed of , a peak altitude of , and covering in about 35 minutes. The spent A10 would descend by brake flaps and parachute to be recovered in the sea and reused.