The Aggregate series was a set of rocket designs developed in 1933-1945 by a research program of Nazi Germany's army. Its greatest
success was the A4, more commonly known as the V-2. The German word Aggregat refers to a group of machines working together.
- When Wernher von Braun began work at the Kummersdorf-West site of the German Army
Weapons Department, near Berlin, on the 1st November 1932 (aged 20), he brought with
him a liquid propellant engine that he and Walter Reidel had built at the Rakenflugplatz,
with the VfR (Verein fur Raumschiffart). After sevaral weeks, the engine was set up in
the part of the test bay allocated to him, and the first firing was made in the evening
of 21st December 1932 under floodlights. Those present were Wernher von Braun,Walter Dornberger,
Heinrich Grunow and Walter Riedel. Unfortunately there was a delay in the ignition process and
fuel clot accumulated in the engine, which exploded within half a second of the planned start,
wich demolished the equipment.
- Thankfully no one was injured and work continued on another engine which Arthur had been working
on under Kummersdorf contract at the Heylandt Works. Rudolf's radical design involved placing
the engine inside the fuel tank to both cool the firing engine and also warm the fuel before it
was injected. This engine was regarded as the first true Kummersdorf engine, and when fired for
the first time in January 1933, functioned perfectly, generating a maximum thrust of 140 kg during
the 60 second burn time. This early success was not the pattern over the following months however,
with just about every part of the equipment failing either separately or together.
- It was not until von Braun adopted Rudolf Nebel's maxim of buying anything that was already
available rather that developping it oneself that real progress was made. A slightly larger
version of Arthr Rudolf's engine was build and a rocket body was made into which the engine
was fitted at the rear, again inside the fuel tank. This became known as the "Aggregate-1"
or A-1, and it took six months to build during 1933. From bottom to top the arrangement was
as follows: the 300 kg thrust engine was mounted inside the fuel tank of 75% Ethyl Alcohol plus
25% water (the water was used to keep the combustion temperature down), while advances in
aluminium-surface hardening had enabled this metal to be used for the combustion chamber.
- Above this integral construction was the Liquid Oxygen tank, again made of amuminium, but with
a fibre-glass internal lining. Then above this was a compressed Nitrogen sphere to force both
propellant components into the engine. All three of these sections were enclosed inside a strong
cylinder which was air-tight and allowed the pressurisation to act equally on both fuel and
oxidiser, by the simple idea of having the LOX tank virtually open within the fuselage structure.
- The engine, designed by Arthur Rudolph, used a pressure-fed propellant system burning alcohol and liquid oxygen, and
produced 300 kgf (660 lbf, 2.9 kN) of thrust for 16 seconds. The rocket was stabilized by a 90 pound gyroscope in the nose, but
there was concern that this might cause problems with the liquid fuels.
- By December everything was ready and several static tests took place successfuly with the tank
half filled. The burn time was limited to 16-17 sec. to keep the weight down, although when fully
loaded with 36,3 kg of fuel and oxidiser the all-up weight was about 140 kg. The heaviest single
component of the A-1 was a 31,75 kg gyroscope fly-wheel mounted on the nose which was to be spun
up to 9.000 rpm by an external electric motor.
- This method of stabilisation had been suggested by the artillery people at Kummersdorf in
parallel with ideas based on the spinning of shells when fired from guns. The gyro would provide
"brute-force" stability when spinning on the centre-line axis and fixed to the rocket structure.
- During the late Autumm of 1933 a number af scale models with centre-line gyros were flown and it
was found that nose-mounting the gyro could never stabilise the rocket, and that it had to be placed
at the rocket's centre of gravity. However, during a engine static test using the complete rocket
on 21st December 1933, the rocket was destroyed in an explosion, probably caused by LOX
leaking into the structure due to vibration during the ignition sequence.
This model never flew.