V-2 Rocket

The V-2 (german: Vergeltungswaffe 2, lit=Retaliation Weapon 2), with the technical name '' Aggregat 4'' (A-4), was the world’s first long-range guided ballistic missile. The missile, powered by a liquid-propellant rocket engine, was developed during the Second World War in Nazi Germany as a "vengeance weapon" and assigned to attack Allied cities as retaliation for the Allied bombings of German cities. The rocket also became the first artificial object to travel into space by crossing the Kármán line (edge of space) with the vertical launch of MW 18014 on 20 June 1944.

Research into military use of long-range rockets began when the graduate studies of Wernher von Braun attracted the attention of the Wehrmacht. A series of prototypes culminated in the A-4, which went to war as the . Beginning in September 1944, over 3,000 were launched by the Wehrmacht against Allied targets, first London and later Antwerp and Liège. According to a 2011 BBC documentary, the attacks from resulted in the deaths of an estimated 9,000 civilians and military personnel, and a further 12,000 forced laborers and Nazi concentration camps prisoners died as a result of their forced participation in the production of the weapons."Am Anfang war die V2. Vom Beginn der Weltraumschifffahrt in Deutschland". In: Utz Thimm (ed.): ''Warum ist es nachts dunkel? Was wir vom Weltall wirklich wissen''. Kosmos, 2006, p. 158, .

The rockets travelled at supersonic speed, impacted without audible warning, and proved unstoppable, as no effective defense existed. Teams from the Allied forces—the United States, the United Kingdom, and the Soviet Union—raced to seize key Nazi manufacturing facilities, procure the Nazis' missile technology, and capture the V-2’s launching sites. Von Braun and over 100 key personnel surrendered to the Americans, and many of the original team ended up working at the Redstone Arsenal. The US also captured enough hardware to build approximately 80 of the missiles. The Soviets gained possession of the manufacturing facilities after the war, re-established production, and moved it to the Soviet Union.

Development history

In the late 1920s, a young Wernher von Braun bought a copy of Hermann Oberth's book, ''Die Rakete zu den Planetenräumen'' (''The Rocket into Interplanetary Spaces''). The world's first large-scale experimental rocket program was Opel-RAK under the leadership of Fritz von Opel and Max Valier, a collaborator of Oberth, during the late 1920s leading to the first manned rocket cars and rocket planes, which paved the way for the Nazi era V2 program and US and Soviet activities from 1950 onwards. The Opel RAK program and the spectacular public demonstrations of ground and air vehicles drew large crowds, as well as caused global public excitement as so-called "Rocket Rumble" and had a large long-lasting impact on later spaceflight pioneers, in particular on Wernher von Braun. The Great Depression ended these activities. Von Opel left Germany in 1930 and emigrated later to France and Switzerland.

Starting in 1930, von Braun attended the Technical University of Berlin, where he assisted Oberth in liquid-fueled rocket motor tests. Von Braun was working on his doctorate when the Nazi Party gained power in Germany. An artillery captain, Walter Dornberger, arranged an Ordnance Department research grant for von Braun, who from then on worked next to Dornberger's existing solid-fuel rocket test site at Kummersdorf. Von Braun's thesis, ''Construction, Theoretical, and Experimental Solution to the Problem of the Liquid Propellant Rocket'' (dated 16 April 1934), was kept classified by the German Army and was not published until 1960. By the end of 1934, his group had successfully launched two rockets that reached heights of .

At the time, Germany was highly interested in American physicist Robert H. Goddard's research. Before 1939, German engineers and scientists occasionally contacted Goddard directly with technical questions. Von Braun used Goddard's plans from various journals and incorporated them into the building of the ''Aggregate'' (A) series of rockets, named for the German word for mechanism or mechanical system.

Following successes at Kummersdorf with the first two Aggregate series rockets, Braun and Walter Riedel began thinking of a much larger rocket in the summer of 1936, based on a projected thrust engine. In addition, Dornberger specified the military requirements needed to include a 1-ton payload, a range of 172 miles with a dispersion of 2 or 3 miles, and transportable using road vehicles.

After the A-4 project was postponed due to unfavorable aerodynamic stability testing of the A-3 in July 1936, English translation 1954.
Braun specified the A-4 performance in 1937, and, after an "extensive" series of test firings of the A-5 scale test model,Christopher, p.111. using a motor redesigned from the troublesome A-3 by Walter Thiel, A-4 design and construction was ordered 1938–39. During 28–30 September 1939, (English: ''The Day of Wisdom'') conference met at Peenemünde to initiate the funding of university research to solve rocket problems.

By late 1941, the Army Research Center at Peenemünde possessed the technologies essential to the success of the A-4. The four key technologies for the A-4 were large liquid-fuel rocket engines, supersonic aerodynamics, gyroscopic guidance and rudders in jet control. At the time, Adolf Hitler was not particularly impressed by the V-2; he opined that it was merely an artillery shell with a longer range and much higher cost.

In early September 1943, Braun promised the Long-Range Bombardment Commission that the A-4 development was "practically complete/concluded", but even by the middle of 1944, a complete A-4 parts list was still unavailable. Hitler was sufficiently impressed by the enthusiasm of its developers, and needed a " wonder weapon" to maintain German morale, so he authorized its deployment in large numbers.

The V-2s were constructed at the Mittelwerk site by prisoners from Mittelbau-Dora, a concentration camp where 20,000 prisoners died.

In 1943, the Austrian resistance group around Heinrich Maier managed to send exact drawings of the V-2 rocket to the American Office of Strategic Services. Location sketches of V-rocket manufacturing facilities, such as those in Peenemünde, were also sent to the Allied general staff in order to enable Allied bombers to carry out airstrikes. This information was particularly important for Operation Crossbow and Operation Hydra, both preliminary missions for Operation Overlord. The group was gradually captured by the Gestapo and most of the members were executed.

Technical details

The A-4 used a 75% ethanol/25% water mixture ( ''B-Stoff'') for fuel and liquid oxygen (LOX) ( ''A-Stoff'') for oxidizer. The water reduced the flame temperature, acted as a coolant by turning to steam and augmented the thrust, tended to produce a smoother burn, and reduced thermal stress.

Rudolf Hermann's supersonic wind tunnel was used to measure the A-4's aerodynamic characteristics and center of pressure, using a model of the A-4 within a 40 square centimeter chamber. Measurements were made using a Mach 1.86 blowdown nozzle on 8 August 1940. Tests at Mach numbers 1.56 and 2.5 were made after 24 September 1940.

At launch the A-4 propelled itself for up to 65 seconds on its own power, and a program motor held the inclination at the specified angle until engine shutdown, after which the rocket continued on a ballistic free-fall trajectory. The rocket reached a height of or 264,000 ft after shutting off the engine.

The fuel and oxidizer pumps were driven by a steam turbine, and the steam was produced by concentrated hydrogen peroxide ( T-Stoff) with sodium permanganate ( Z-Stoff) catalyst. Both the alcohol and oxygen tanks were an aluminum-magnesium alloy.

The turbopump, rotating at 4000 rpm, forced the alcohol and oxygen into the combustion chamber at 125 liters (33 US gallons) per second, where they were ignited by a spinning electrical igniter. Thrust increased from 8 tons during this preliminary stage whilst the fuel was gravity-fed, before increasing to 25 tons as the turbopump pressurised the fuel, lifting the 13.5 ton rocket. Combustion gases exited the chamber at , and a speed of 2000 m (6500 feet) per second. The oxygen to fuel mixture was 1.0:0.85 at 25 tons of thrust, but as ambient pressure decreased with flight altitude, thrust increased until it reached 29 tons.Zaloga 2003 p19 The turbopump assembly contained two centrifugal pumps, one for the alcohol, and one for the oxygen, both connected to a common shaft. Hydrogen peroxide converted to steam, using a sodium permanganate catalyst powered the pump, which delivered 55 kg (120 pounds) of alcohol and 68 kg (150 pounds) of liquid oxygen per second to a combustion chamber at 1.5 MPa (210 psi).

Dr. Thiel's development of the 25 ton rocket motor relied on pump feeding, rather than on the earlier pressure feeding. The motor used centrifugal injection, while using both regenerative cooling and film cooling. Film cooling admitted alcohol into the combustion chamber and exhaust nozzle under slight pressure through four rings of small perforations. The mushroom-shaped injection head was removed from the combustion chamber to a mixing chamber, the combustion chamber was made more spherical while being shortened from 6 to 1 foot in length, and the connection to the nozzle was made cone shaped. The resultant 1.5 ton chamber operated at a combustion pressure of 1.52 MPa (220 psi). Thiel's 1.5 ton chamber was then scaled up to a 4.5 ton motor by arranging three injection heads above the combustion chamber. By 1939, eighteen injection heads in two concentric circles at the head of the 3 mm (0.12-inch) thick sheet-steel chamber, were used to make the 25 ton motor.

The warhead was another source of trouble. The explosive employed was amatol 60/40 detonated by an electric contact fuze. Amatol had the advantage of stability, and the warhead was protected by a thick layer of glass wool, but even so it could still explode in the re-entry phase. The warhead weighed and contained of explosive. The warhead's percentage by weight that was explosive was 93%, a very high percentage when compared with other types of munition.

A protective layer of glass wool was also used for the fuel tanks so the A-4 did not have a tendency to form ice, a problem which plagued other early ballistic missiles such as the balloon tank-design SM-65 Atlas which entered US service in 1959. The tanks held of ethyl alcohol and of oxygen.

The V-2 was guided by four external rudders on the tail fins, and four internal graphite vanes in the jet stream at the exit of the motor. These 8 control surfaces were controlled by Helmut Hölzer's analog computer, the , via electrical-hydraulic servomotors, based on electrical signals from the gyros. The Siemens ''Vertikant'' LEV-3 guidance system consisted of two free gyroscopes (a horizontal for pitch and a vertical with two degrees of freedom for yaw and roll) for lateral stabilization, coupled with a PIGA accelerometer, or the Walter Wolman radio control system, to control engine cutoff at a specified velocity. Other gyroscopic systems used in the A-4 included Kreiselgeräte's SG-66 and SG-70. The V-2 was launched from a pre-surveyed location, so the distance and azimuth to the target were known. Fin 1 of the missile was aligned to the target azimuth.

Some later V-2s used " guide beams", radio signals transmitted from the ground, to keep the missile on course, but the first models used a simple analog computer that adjusted the azimuth for the rocket, and the flying distance was controlled by the timing of the engine cut-off, '' Brennschluss'', ground-controlled by a Doppler system or by different types of on-board integrating accelerometers. Thus, range was a function of engine burn time, which ended when a specific velocity was achieved. Just before engine cutoff, thrust was reduced to eight tons, in an effort to avoid any water hammer problems a rapid cutoff could cause.

Dr. Friedrich Kirchstein of Siemens of Berlin developed the V-2 radio control for motor-cut-off (german: Brennschluss). For velocity measurement, Professor Wolman of Dresden created an alternative of his Doppler tracking system in 1940–41, which used a ground signal transponded by the A-4 to measure the velocity of the missile. By 9 February 1942, Peenemünde engineer Gerd had documented the radio interference area of a V-2 as around the "Firing Point", and the first successful A-4 flight on 3 October 1942, used radio control for . Although Hitler commented on 22 September 1943 that "It is a great load off our minds that we have dispensed with the radio guiding-beam; now no opening remains for the British to interfere technically with the missile in flight", about 20% of the operational V-2 launches were beam-guided. The Operation Pinguin V-2 offensive began on 8 September 1944, when (English: 'Training and Testing Battery 444') launched a single rocket guided by a radio beam directed at Paris. Wreckage of combat V-2s occasionally contained the transponder for velocity and fuel cutoff.

The painting of the operational V-2s was mostly a ragged-edged pattern with several variations, but at the end of the war a plain olive green rocket also appeared. During tests the rocket was painted in a characteristic black-and-white chessboard pattern, which aided in determining if the rocket was spinning around its longitudinal axis.

The original German designation of the rocket was "V2", unhyphenated – exactly as used for any Third Reich-era "second prototype" example of an RLM-registered German aircraft design – but U.S. publications such as ''Life'' magazine were using the hyphenated form "V-2" as early as December 1944.

Testing

The first successful test flight was on 3 October 1942, reaching an altitude of . On that day, Walter Dornberger declared in a speech at Peenemünde:

Two test launches were recovered by the Allies: the Bäckebo rocket, the remnants of which landed in Sweden on 13 June 1944, and one recovered by the Polish resistance on 30 May 1944 from Blizna and transported to the UK during Operation Most III. The highest altitude reached during the war was (20 June 1944). Test launches of V-2 rockets were made at Peenemünde, Blizna and Tuchola Forest, and after the war, at Cuxhaven by the British, White Sands Proving Grounds and Cape Canaveral by the U.S., and Kapustin Yar by the USSR.

Various design issues were identified and solved during V-2 development and testing:
:* To reduce tank pressure and weight, high flow turbopumps were used to boost pressure.
:* A short and lighter combustion chamber without burn-through was developed by using centrifugal injection nozzles, a mixing compartment, and a converging nozzle to the throat for homogeneous combustion.
:* Film cooling was used to prevent burn-through at the nozzle throat.
:* Relay contacts were made more durable to withstand vibration and prevent thrust cut-off just after lift-off.
:* Ensuring that the fuel pipes had tension-free curves reduced the likelihood of explosions at .
:* Fins were shaped with clearance to prevent damage as the exhaust jet expanded with altitude.
:* To control trajectory at liftoff and supersonic speeds, heat-resistant graphite vanes were used as rudders in the exhaust jet.

Air burst problem

Through mid-March 1944, only four of the 26 successful Blizna launches had satisfactorily reached the Sarnaki target area due to in-flight breakup () on re-entry into the atmosphere. (As mentioned above, one rocket was collected by the Polish Home Army, with parts of it transported to London for tests.) Initially, the German developers suspected excessive alcohol tank pressure, but by April 1944, after five months of test firings, the cause was still not determined. Major-General Rossmann, the Army Weapons Office department chief, recommended stationing observers in the target area – May/June, Dornberger and von Braun set up a camp at the centre of the Poland target zone. After moving to the Heidekraut, SS Mortar Battery 500 of the 836th Artillery Battalion (Motorized) was ordered on 30 August to begin test launches of eighty 'sleeved' rockets. Testing confirmed that the so-called 'tin trousers' – a tube designed to strengthen the forward end of the rocket cladding – reduced the likelihood of air bursts.

Production

On 27 March 1942, Dornberger proposed production plans and the building of a launching site on the Channel coast. In December, Speer ordered Major Thom and Dr. Steinhoff to reconnoiter the site near Watten. Assembly rooms were established at Peenemünde and in the Friedrichshafen facilities of Zeppelin Works. In 1943, a third factory, Raxwerke, was added.

On 22 December 1942, Hitler signed the order for mass production, when Albert Speer assumed final technical data would be ready by July 1943. However, many issues still remained to be solved even by the autumn of 1943.

On 8 January 1943, Dornberger and von Braun met with Speer. Speer stated, "As head of the Todt organisation I will take it on myself to start at once with the building of the launching site on the Channel coast," and established an A-4 production committee under Degenkolb.

On 26 May 1943, the Long-Range Bombardment Commission, chaired by AEG director Petersen, met at Peenemünde to review the V-1 and V-2 automatic long-range weapons. In attendance were Speer, Air Marshal Erhard Milch, Admiral Karl Dönitz, Col. General Friedrich Fromm, and Karl Saur. Both weapons had reached the final stage of development, and the commission decided to recommend to Hitler that both weapons be put into mass production. As Dornberger observed, "The disadvantages of the one would be compensated by the other's advantages."

On 7 July 1943, Major General Dornberger, von Braun, and Dr. Steinhof briefed Hitler in his Wolf's Lair. Also in attendance were Speer, Wilhelm Keitel, and Alfred Jodl. The briefing included von Braun narrating a film showing the successful launch on 3 October 1942, with scale models of the Channel coast firing bunker, and supporting vehicles, including the . Hitler then gave Peenemünde top priority in the German armaments program stating, "Why was it I could not believe in the success of your work? if we had had these rockets in 1939 we should never have had this war..." Hitler also wanted a second launch bunker built.

Saur planned to build 2,000 rockets per month, between the existing three factories and the Nordhausen Mittelwerk factory being built. However, alcohol production was dependent upon the potato harvest.

A production line was nearly ready at Peenemünde when the Operation Hydra attack occurred. The main targets of the attack included the test stands, the development works, the Pre-Production Works, the settlement where the scientists and technicians lived, the Trassenheide camp, and the harbor sector. According to Dornberger, "Serious damage to the works, contrary to first impressions, was surprisingly small." Work resumed after a delay of four to six weeks, and because of camouflage to mimic complete destruction, there were no more raids over the next nine months. The raid resulted in 735 lives lost, with heavy losses at Trassenheide, while 178 were killed in the settlement, including Dr. Thiel, his family, and Chief Engineer Walther. The Germans eventually moved production to the underground ''Mittelwerk'' in the Kohnstein where 5,200 V-2 rockets were built with the use of forced labour.

Launch sites

Following the Operation Crossbow bombing, initial plans for launching from the massive underground Watten, Wizernes and Sottevast bunkers or from fixed pads such as near the Château du Molay were dropped in favour of mobile launching. Eight main storage dumps were planned and four had been completed by July 1944 (the one at Mery-sur-Oise was begun in August 1943 and completed by February 1944). The missile could be launched practically anywhere, roads running through forests being a particular favourite. The system was so mobile and small that only one was ever caught in action by Allied aircraft, during the Operation Bodenplatte attack on 1 January 1945 near Lochem by a USAAF 4th Fighter Group aircraft, although Raymond Baxter described flying over a site during a launch and his wingman firing at the missile without hitting it.

It was estimated that a sustained rate of 350 V-2s could be launched per week, with 100 per day at maximum effort, given sufficient supply of the rockets.

Operational history

The LXV ''Armeekorps'' z.b.V. formed during the last days of November 1943 in France commanded by ''General der Artillerie'' z.V. Erich Heinemann was responsible for the operational use of V-2. Three launch battalions were formed in late 1943, ''Artillerie Abteilung'' 836 (Mot.), Grossborn, Artillerie Abteilung 485 (Mot.), Naugard, and ''Artillerie Abteilung'' 962 (''Mot.''). Combat operations commenced in Sept. 1944, when training Batterie 444 deployed. On 2 September 1944, the SS ''Werfer-Abteilung'' 500 was formed, and by October, the SS under the command of SS Lt. Gen Hans Kammler, took operational control of all units. He formed ''Gruppe Sud'' with Art. Abt. 836, Merzig, and ''Gruppe Nord'' with Art. Abt. 485 and ''Batterie'' 444, Burgsteinfurt and The Hague.

After Hitler's 29 August 1944 declaration to begin V-2 attacks as soon as possible, the offensive began on 7 September 1944 when two were launched at Paris (which the Allies had liberated less than two weeks earlier), but both crashed soon after launch. On 8 September a single rocket was launched at Paris, which caused modest damage near Porte d'Italie. Two more launches by the 485th followed, including one from The Hague against London on the same day at 6:43 pm. – the first landed at Staveley Road, Chiswick, killing 63-year-old Mrs. Ada Harrison, three-year-old Rosemary Clarke, and Sapper Bernard Browning on leave from the Royal Engineers, and one that hit Epping with no casualties. Upon hearing the double-crack of the supersonic rocket (London's first ever), Duncan Sandys and Reginald Victor Jones looked up from different parts of the city and exclaimed "That was a rocket!", and a short while after the double-crack, the sky was filled with the sound of a heavy body rushing through the air.

The British government, concerned about spreading panic or giving away vital intelligence to German forces, initially attempted to conceal the cause of the explosions by making no official announcement, and euphemistically blaming them on defective gas mains. The public did not believe this explanation and therefore began referring to the V-2s as "flying gas mains". The Germans themselves finally announced the V-2 on 8 November 1944 and only then, on 10 November 1944, did Winston Churchill inform Parliament, and the world, that England had been under rocket attack "for the last few weeks".

In September 1944, control of the V-2 mission was taken over by the Waffen-SS and Division z.V.

Positions of the German launch units changed a number of times. For example, ''Artillerie Init 444'' arrived in the southwest Netherlands (in Zeeland) in September 1944. From a field near the village of Serooskerke, five V-2s were launched on 15 and 16 September, with one more successful and one failed launch on the 18th. That same date, a transport carrying a missile took a wrong turn and ended up in Serooskerke itself, giving a villager the opportunity to surreptitiously take some photographs of the weapon; these were smuggled to London by the Dutch Resistance. After that the unit moved to the woods near Rijs, Gaasterland in the northwest Netherlands, to ensure that the technology did not fall into Allied hands. From Gaasterland V-2s were launched against Ipswich and Norwich from 25 September (London being out of range). Because of their inaccuracy, these V-2s did not hit their target cities. Shortly after that only London and Antwerp remained as designated targets as ordered by Adolf Hitler himself, Antwerp being targeted in the period of 12 to 20 October, after which time the unit moved to The Hague.

Targets

Over the following months about 3,172 V-2 rockets were fired at the following targets:

: Belgium, 1,664: Antwerp (1,610), Liège (27), Hasselt (13), Tournai (9), Mons (3), Diest (2)
: United Kingdom, 1,402: London (1,358), Norwich (43), Ipswich (1)
: France, 76: Lille (25), Paris (22), Tourcoing (19), Arras (6), Cambrai (4)
: Netherlands, 19: Maastricht (19)
: Germany, 11: Remagen (11)
Antwerp, Belgium was a target for a large number of V-weapon attacks from October 1944 through to the virtual end of the war in March 1945, leaving 1,736 dead and 4,500 injured in greater Antwerp. Thousands of buildings were damaged or destroyed as the city was struck by 590 direct hits. The largest loss of life by a single rocket attack during the war came on 16 December 1944, when the roof of the crowded Cine Rex was struck, leaving 567 dead and 291 injured.

An estimated 2,754 civilians were killed in London by V-2 attacks with another 6,523 injured, which is two people killed per V-2 rocket. However, this understates the potential of the V-2, since many rockets were misdirected and exploded harmlessly. Accuracy increased over the course of the war, particularly for batteries where the (radio guide beam) system was used. Missile strikes that found targets could cause large numbers of deaths – 160 were killed and 108 seriously injured in one explosion at 12:26 pm on 25 November 1944, at a Woolworth's department store in New Cross, south-east London.
British intelligence sent false reports via their Double-Cross System implying that the rockets were over-shooting their London target by . This tactic worked; more than half of the V-2s aimed at London landed outside the London Civil Defence Region.Jones RV; Most Secret War 1978 Most landed on less-heavily populated areas in Kent due to erroneous recalibration. For the remainder of the war, British intelligence kept up the ruse by repeatedly sending bogus reports implying that the rockets were now striking the British capital with heavy loss of life.Blitz Street; Channel 4, 10 May 2010

Possible use during Operation Bodenplatte

At least one V-2 missile on a mobile '' Meillerwagen'' launch trailer was observed being elevated to launch position by a USAAF 4th Fighter Group pilot defending against the massive New Year's Day 1945 Operation Bodenplatte strike by the Luftwaffe over the northern German attack route near the town of Lochem on 1 January 1945. Possibly, from the potential sighting of the American fighter by the missile's launch crew, the rocket was quickly lowered from a near launch-ready 85° elevation to 30°.

Tactical use on German target

After the US Army captured the Ludendorff Bridge during the Battle of Remagen on 7 March 1945, the Germans were desperate to destroy it. On 17 March 1945, they fired eleven V-2 missiles at the bridge, their first use against a tactical target and the only time they were fired on a German target during the war. They could not employ the more accurate device because it was oriented towards Antwerp and could not be easily adjusted for another target. Fired from near Hellendoorn, the Netherlands, one of the missiles landed as far away as Cologne, to the north, while one missed the bridge by only . They also struck the town of Remagen, destroying a number of buildings and killing at least six American soldiers.

Final use

The final two rockets exploded on 27 March 1945. One of these was the last V-2 to kill a Britis