A Rocket History
Article by Len Targett
Our late Member Len Targett wrote for the Newsletter, a most interesting article covering a brief history of rockets culminating in the German V2 Rocket, a project in which he was intimately involved during the last War.
As Major Len Targett, he was attached to The Special Projectile Operations Group, which was the team formed to investigate all aspects of V2 development, associated equipment and firing techniques. This group was responsible for the compilation of the final report on the task.
The origin of the rocket was in China following the invention of gunpowder in 1200 AD and was used aggressively by the Chinese who went to war with "arrows of fire". There are also records of similar types of weapons being used by the Venetians in the year 1380. Little development took place until 1580 when a German Dr. Haas experimented with gunpowder mixtures which gave better combustion resulting in greater distances but used a stick for stability. Between 1668 and 1779 rockets with metal bodies were made and a lot of research was done by William Congrave at Woolwich Arsenal in London, successful weapons were manufactured and added to the armoury. The Duke of Wellington raised The Royal Rocket Regiment and Nelson at the same time trained a section of the Marines for rocket duties. The regiment had quite a useful action at Waterloo.
In 1850 Dr. Hale added side vents to make them spin and so did away with the stick. Up to 1909, development was still with gunpowder and advances were made in life saving equipment, signals and entertainment. At this time the German firm Krupps acquired a patent on fuels based on nitro-glycerine, as a result, advance was rapid and led to the combustion of fuels in cavities instead of at the end which considerably increased the thrust and range.
During the first world war, Dr. Goddard in America concentrated on liquid fuels for propelling vehicles etc. From his findings a more controllable rocket with twice the thrust for the same size and range of 7500 ft was achieved.
In 1923 racing cars were being fitted with rockets and activity was boosted by a paper on space travel by the German Interplanetary Society and Prof. Hans Orberths, interest was also being shown by space societies in the USA, Russia and England.
By 1926, the German team had produced bi-fueled rockets with a mile range and demonstrated these on an international basis to show their possible use for postal travel.
It was after the effects of these demonstrations by the German Society under the Professor and two founder members, Willie Smidt and Willy Ley, and also Von Braun who was then a student, that a significant change took place, and the Society was given official recognition, as a result of which a number of nations i.e. U.S.A., Russia and England realised the potential value of the use of the rocket as a weapon.
The Artillery Research Dept of the Wermacht sent Captain Dornberger to see a demonstration and examine their set up. He was very taken with it's potential as a weapon and persuaded the Wermacht to allocate funds and a proving ground at Kamnersdorf West, and to put him in charge of further research. Thus the Society was absorbed into the army, the personnel transferred, and Dornberger raised the German Rocket Regiment under his control.
Progress was slow but they did produce a flying model weighing 333 lbs. Followed by a bigger version designated (A1), with encouraging results, it was unstable but all agreed it was on the right lines. Interest was fading due to the success of the flying Bomb and Hitler called for a report. Work on a larger missile the (A2) was well advanced but Dornberger needed more time before showing Hitler. He was persuaded by the team to take a chance, Von Braun was particularly optimistic.
The show went ahead to the General Staff and to Hitler in 1933 and the A2 flew 8,000 ft. It was in effect a very good show with one exception, the staff agreed on it's war potential and the need to enlarge the facilities. Goering said it was worth further support but needed more examination before being granted top priority, since he dealt with things that flew, he would "look into it". Dornberger was alarmed at this, and asked for their support for a meeting with Hitler, since Goering's tactics were well known. This was arranged and Hitler issued instructions that the Regiment remain under the Army and move to the research Station at Peenemunder which was situated on an island in the Baltic some 70 miles from Stettin and which had a firing range of 330 miles over open water. It was here that real progress was made, a higher priority granted and skilled people made available. An(A3) type was fired which stood 22ft. high carrying a payload of 100/l50 lbs. and this worked well except that there was not enough energy in the fuel to maintain adequate volume and pressure to the pumps. Clearly a different fuel had to be employed.
The answer was found in the work done by Dr.Walther with steam produced by chemical reaction between permanganate of Potash and concentrated hydrogen peroxide, giving super heated steam. Dr.Walther had made the engines for midget submarines driving a 22 inch turbine developing 4000 HP. His work also had far reaching uses in the war effort such as take off boosters for aircraft.
It was clear that a complete redesign of the fuel feed was a must. Dr.Walther designed an engine that was not only lighter than the original but gave an increased Velocity from 2590 to 4000 meters per second. The project was given top priority and designated (A4).
It was after a great effort that a stable missile was fired in 1942 which was 3O ft. high with a range of 118 miles. Hitler said he wanted to see a firing himself and saw two very successful launches in Oct. 1942 after instructing Reich Minister Speer to put the rocket into production at Friedrichhaven in the old airship sheds, with all speed and at any cost
For some time fears of an air raid on Peenemunder had been expressed and Speer had set up Shadow Research Plants at Nordmausen and Blitzna, so that by the time we raided both these establishments were in operation. The raid took place on 17/18th. Aug 1943.
While the raid did not destroy the working buildings due to the path finders flares falling short, the bombs landed on buildings housing the scientists and the forced labour barracks. 700 people were killed of which 374 were forced labour.
The failure of the main objective was more than compensated by the scientists killed, amongst whom were Dr Walther, Dr. Theil and Reidle, who were not only vital to the rocket on guidance systems, but atomic weapons and warheads. in fact the guidance system for the A4 was never a success, and had to be manually set with gyroscopes.
The top level position in Germany at this time was chaotic and politics led to quarrels among the leadership, the rocket team was split up. Suspected of delaying the finalising of the arrangements; Prof. Von Braun was investigated by the SS and moved to research, Dornberger to the Regiment. Speer took over all manufacture, and Himmler research. It was lucky for us that this caused a delay so that it was not until June 1944 that the attacks on London began. The performance in the raids showed a lot more work was needed but Von Braun managed to continue his work and designed a number larger rockets to ranges of 8000 miles and 50 miles high.
The dimensions of the A4 which we knew as the V2 were:-
The average run time for the engine was 1 minute in which enough energy was generated to propel the rocket 185 miles travelling 2220 miles per hour to a height of 16 miles to cut off point, its highest ceiling trajectory was 56 miles with 2 tons of explosives. It was fired from a portable platform and ignited by a Catherine wheel type firework placed in the combustion chamber by remote control.
Interest in the future of rockets was taken very seriously by the U.S.A. and Russia, and as many of you will know, personnel who had been engaged on rockets were rounded up and a selected group divided between U.S.A. and Russia.
Thus the history continued into the beginning of the Space age.
Len continues the story with "A Rocket History.Part ll".
Rocket History Part II"Following my previous article on the V2 rocket, I have been asked about the method of the control of flight. It is only possible to give a very brief resume of such a complicated system.
To start with there was no satisfactory radio control, and whilst an area was reserved on the control compartment for housing any future development, the control was a combination of the method used to direct a gun and a gyroscopically controlled apparatus, to determine the line of flight from the velocity at engine cut off.
This is a schematic of the controls, and illustrations of the components actuated by the gyros. These were the function of the electrical circuits concerned with the steering and stability of the rocket in flight, also the operation of the fuel and other valves associated with the propulsion unit. They were housed in a four sectioned control compartment in the nose cone. The nose cone containing two batteries, two motor alternators with their frequency regulators, two gyroscopes, a control amplifier, a sequence switch, an emergency switch box and a number of relays.
The actual steering of the rocket was controlled by four carbon vanes operating in the propelling gas flow. These in turn were controlled by four servo mechanisms. There were also four small vanes fitted to the large fixed fins on the tail.
The electrical power for operating the system and fuel valves, was obtained from a 32 Volt lead acid battery providing a discharge of about 100 amps for five minutes, the battery comprising two sections of eight cells each. A second battery was used to provide signals between the two gyroscopes and the control amplifier, this was a 30 Volt Nickel Cadmium type battery providing 300 Milli-amps for approximately five minutes.
The steering of the rocked was by two gyroscopes operated from a 500 cycle three phase supply, running from a motor alternator drawing power from the lead acid battery. One gyro was used to control the turning of the rocket into its trajectory and the other, roll and yaw. The control amplifier accepted signals from the gyros and passed them to the actual steering mechanism.
The second 500 cycle alternator similar to the one used for driving the gyros and running off the same battery, provided the power to operate the control amplifier. The gyros ran at 30,000 rpm. The motor alternators were small machines which took DC at one end and generated 40 volts 3 phase. A separate frequency regulator was used with each machine to maintain the frequency at 500 cycles against battery variations. The signals from the control amplifier were taken to servo mechanisms mounted in a ring in the tail, these controlled the movement of the carbon vanes. The outer vanes on the fins associated with the roll and yaw were directly coupled to the carbon vales by a series of mechanical levers and chain drives. The outer vanes on the fins on the pitch axis were not connected with the carbon vanes controlling the pitch but were driven by separate trim motors which were brought into operation when the roll and yaw vanes were out of synchronisation.
A sequence switch was fitted to control the operation of certain valves and to actuate the turning of the rocket from it's vertical path onto its trajectory setting. It was also used to check the settings when the rocket was being set up, including the systems brought into use when the weapon was linked and controlled from the ground to carry out pre firing preparations.
That concludes the general overall picture but for those who would like a little more detail, the following on Gyros may be of interest:-
The two gyros are illustrated here. They were similar in design and the motors were driven from the current supplied from the No. 2 alternator at a speed of 30,000 rpm. When running up to speed, the inner precision axis was maintained vertical by a stabilising motor under the mounting for the rotor housing, controlled by a gravity switch on the side of the mounting. The contact openings on this switch were very small, of the order of 1/10th mm. The contacts of this switch controlled the energisation of the coils of the stabilising motor inside, which was a magnetised disc producing a torque to counteract the tendency of the torque axis to move from the vertical.
A similar stabilising motor was fitted to the end of the gyro to stop the torque axis from moving from a position at right angles to the middle axis. This motor was actuated from the contacts of a sensitive polarised relay, the tongue of which was normally centre stable, moving from side to side depending on the direction of the current flowing in the relay winding, which was connected to the wipers of the pick-off potentiometer. These were wire wound and connected in parallel to the signalling battery. The resistance of each winding of each potentiometer was 100 ohms.
The wipers were very thin wire, bent into the shape of a V, moving over the potentiometer windings. The connections between the fixed and moving parts of the gyro were made though point swivel contacts, accurately aligned.
The pitch gyro was fitted with a small motor known as the programme motor to control the turning of the rocket into it's trajectory and consisted of a ratchet driven wheel which turned a small camshaft through a worm drive. The ratchet was driven by an electric magnet energised by interrupted DC current at 45 ips supplied by a reed interrupter fitted in the base of the sequence switch. Also on this camshaft was a pulley driven by an arm fixed to the shaft. This pulley wound up a brass tape which extended over a circular housing accommodating the front pick-off potentiometer.
When it was desired to tilt the rocket in flight, the programme motor cam shaft revolved and the brass tape wound into it's pulley causing the circular housing and potentiometer to be slowly rotated, giving a signal to the control amplifier which was transmitted to the pitch vanes.