cruise missiles

The earliest developments in unmanned guided vehicles took place within the context of weaponization.  One of the first such devices, created during World War I, was a small propeller-driven aircraft called the Kettering Aerial Torpedo.  This 530 pound flying bomb, nicknamed the "Bug," was launched off guide rails towards it's intended target.  It's primitive in-flight guidance system provided only stability and no real directional control.  Upon reaching it's destination a preset timing mechanism would cut the plane's four cylinder gas engine after which the wings would be disconnected and the bomb-bearing fuselage would fall to earth, detonating on impact.

Kettering "Bug" in preparation for launch

The V1 flying Bomb

The Germans performed experiments with autopiloted aircraft in the 1930s, but proposals made to the German military in 1939 and 1941 to develop flying bombs were rejected. In June 1942, however, increasing RAF bomb raids on German cities, and rising losses of Luftwaffe bombers over England in attempts to retaliate, persuaded the Luftwaffe to consider new options. Work on the V-2 long-range rocket was encountering difficulties, and the V-2 was an Army project in any case. The Luftwaffe investigated and approved development of a small, cheap flying bomb, with a range of about 250 kilometres (155 miles) and an 800 kilogram (1,760 pound) warhead, that could hit a city-sized area, evading interception by flying in at high speed and low altitude. The project was given the cover designation of "Flak Ziel Geraet (FZG)", or "anti-aircraft target apparatus".

Propulsion for the new flying bomb was provided by the "pulsejet", which had been invented by Paul Schmidt in the early 1930s, with development picked up by the Army Weapons Office in 1937. The pulsejet was little more than a "stovepipe", with its sole moving part consisting of a shutter assembly inside the air intake. The simplicity and low cost of this engine was a major factor in the Luftwaffe's decision to pursue flying bomb development. Air entering into the pulsejet was mixed with fuel and the mixture ignited by spark plugs. The combustion of the mixture slammed the intake shutters closed, and produced a burst of thrust out the exhaust. The shutters then opened again in the airflow. The production engine would perform this cycle about 42 times a second. This pulsed operation caused the engine to emit a loud low throbbing sound that would presently become familiar over the English countryside.

Schmidt's pulsejet was a crude engine. Throttling it was difficult at best, it could only operate effectively at low altitudes, and the shutters tended to wear out quickly, but none of these issues were important in an expendable robot weapon, and it had major advantages. It was simple, cheap, and powerful, with a thrust of 200 kN (270 kgp / 600 lbf). Furthermore, it could use low-grade gasoline as a fuel, rather than precious high-octane aviation fuel.

Three companies collaborated in building the flying bomb. Fiesler built the airframe; Argus, the employer of Paul Schmidt, built the pulsejet engine; and Askania built the guidance system. A glide test of the flying bomb was performed from a Focke Wulf FW-200 Kondor bomber in early December 1942, followed by a powered flight on Christmas Eve. The first powered flight only went a kilometer, and the early prototypes showed a distressing tendency to crash. To resolve these problems, a piloted flying bomb was developed, with the warhead replaced by a cockpit in which a test pilot could fly the machine while lying prone. Test flights were performed with the tiny and daring female test pilot Hanna Reitsch at the controls, and helped resolve the problems.

On 26 May 1943, top Nazi officials visited the test facility at Peenemunde on the Baltic, to evaluate progress on the flying bomb. They concluded that the weapon should be put into full-scale production, and work was accelerated on completing development; establishing an operational unit to fire the weapons; and constructing launch sites. A hundred launch sites were to be built in the Pas de Calais area in northwest France, capable of launching a thousand flying bombs a day. London was only about 200 kilometres (120 miles) from the launch sites.

The flying bomb was refined into a production prototype version, codenamed "Kirshkern (Cherrystone)", that was much superior to the initial prototypes. In production, the weapon was officially designated the "Fiesler Fi-103" or "FZG-76", but was referred to by Nazi propaganda as the "V-1", for "Vergeltungswaffe Einz (Vengeance Weapon 1)".

RAF photo-reconnaissance aircraft had been observing the strange goings-on at Peenemunde since the middle of May 1942, and though Allied intelligence wasn't sure about what was going on, it was clearly nothing good. The RAF launched OPERATION HYRDA, a major bomb raid on Peenemunde, in the late summer of 1943, though it did not greatly slow down German development efforts. Shortly thereafter, the USAAF bombed the launching sites in the Pas de Calais, destroying most of them.

On 28 November 1943, an RAF photo-reconnaissance aircraft took pictures of Peenemunde, and a sharp-eyed photographic analyst, Flight Officer Babington Smith, spotted a prototype flying bomb on a launch ramp at Peenemunde. British intelligence began to see what the Germans were up to, and estimated that the Germans would be able to start launching these new weapons against England in a matter of weeks. Bombings of new launch sites under construction were stepped up. However, by this time the flying bomb was in production, and the new launch sites were more easily concealed. Several flying bombs were launched towards Sweden in last-minute tests to determine their range and other performance characteristics, and on 13 June 1944 the first V-1s were launched towards London.

Only about ten missiles were fired that day. The commandant in charge of the launch sites had been ordered to launch, but he was not quite ready to begin full-scale launch operations at that time. He did the minimum required of him, then returned to completing his preparations. The "Flying Bomb Blitz" began in earnest on 15 June 1944, with 244 fired at London and 50 fired at Southampton. 144 crossed the English coast; 73 managed to reach London; some were shot down; most of the rest landed south of the Thames; and a few hit Southampton. One went wildly astray and ended up in Norfolk.

Characteristics

The V-1 was an odd and ingenious weapon, designed to be cheaply built in large numbers. Early production items were largely made of metal, though wooden wings were quickly introduced. The V-1 was directed to its target by a simple guidance system, which incorporated a set of gyroscopes driven by compressed air to keep the missile stable; a magnetic compass to control bearing; and barometric altimeter to control altitude.

   FI-103 / V-1:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                5.4 meters          17 feet 8 inches
   length                  8.3 meters          27 feet 4 inches
   total weight            2,160 kilograms     4,760 pounds
   warhead weight          850 kilograms       1,870 pounds

   speed                   645 KPH             400 MPH / 350 KT
   range                   260 kilometres      160 MI / 140 NMI
   _____________________   _________________   _______________________

The flying bomb was typically set to fly at an altitude of about 600 meters (2,000 feet) under the control of the barometric altimeter. A spinner on the nose armed the warhead after about 100 kilometres (60 miles) of flight, and determined when the weapon would fall to earth. Some sources claim that this function was performed by a simple clock, not a nose spinner. Illustrations are ambiguous on this issue, and it is possible that different production runs used different systems.

The little aircraft's wings had no control surfaces. The V-1 was directed by the rudder and elevators on its tail assembly. Since there was no way the flying bomb could manoeuvre anyway, such a crude approach was both adequate and cheap. When the guidance system determined that the missile was over its target, it locked the control surfaces and popped out spoilers under the tailplane to put the bomb into a steep dive. Usually, though not always, this stalled the engine. The abrupt cutoff of the loud buzz inspired terror, since it meant there would be a terrific explosion a few seconds later.

The V-1's warhead included a electrical fuse; a backup mechanical fuse; and a time-delay fuse, to ensure that the weapon destroyed itself if the other fuses failed to work. The fusing system was very reliable, and very few V-1s were duds. Early V-1 production had a fuel capacity of 640 litres (169 US gallons). Flight time from launch to impact was usually about 22 minutes. Accuracy was very poor, with impacts scattered all over south-eastern England.

The V-1 was prepared for launch by filling up its fuel tank, installing a battery, and charging up the compressed air tanks for the gyroscopes. It was then trollied to a demagnetized area to check the missile's magnetic compass and set up the guidance system in accordance with the planned target coordinates.

Since the Argus pulsejet engine couldn't produce effective thrust until the flying bomb was up to flight speed, the V-1 was launched off a 48 meter (157 foot) long ramp using a steam catapult system, designed by the Walter company. The ramp contained a slot fitted with a dumbbell-shaped piston, and the flying bomb sat on a simple trolley that was linked to the piston. The piston was held in place with a shear pin. A cart containing a reaction chamber and tanks of with hydrogen peroxide (HO) and granules of potassium permanganate (KMnO4) catalyst was connected to a chamber at the base of the ramp whose other end was plugged by the piston. When the hydrogen peroxide was pumped over the potassium permanganate, it was converted into large quantities of hot steam that built up pressure against the piston. When the pressure built up to a certain level, it broke the piston's shear pin and the trolley rapidly moved up the ramp. The V-1 left the ramp at a speed of about 400 KPH (250 MPH), while the piston shot out into the surrounding terrain and the trolley fell off the weapon. After a firing, the launch ramp had to be swept off by personnel clad in protective clothing -- the fuel spatterings were corrosive.

The V-1 could be fitted with a poison gas warhead that could be loaded up with the new secret, highly lethal German nerve gases. However, fear of retribution in kind kept Hitler from performing poison gas attacks, as German gas warfare experts wrongly believed that the Allies had nerve gases as well. It is unclear how effective V-1s armed with nerve-gas warheads would have been in any case, since even though nerve gases are deadly in extremely low concentrations, an effective nerve gas attack requires a degree of target saturation that might have not been possible with the V-1. High explosive warheads may well have been just as or more destructive.

Some of the V-1s were fitted with a radio transmitter and a trailing antenna wire so that their flight could be monitored. In some cases, the bombs were "shadowed" by fast aircraft like the Messerschmitt 410 twin-engine fighter to observe their flight. A few of the bombs were also fitted with a cage to accommodate 23 one-kilogram incendiary bombs, or a cardboard tube full of propaganda leaflets that was ejected before the V-1 entered its terminal dive. The tube included a small black-powder charge that dispersed the leaflets.

The propaganda leaflets amount to an interesting story in themselves. They included tales of the atrocities against civilians by Allied bombing raids against the Reich, complete with lurid pictures of mangled corpses; propaganda "news" about, say, the vulnerability of Lancaster bombers and how many had been shot down; and also sometimes included copies of letters written home by Allied prisoners of war (POWs) in German hands giving glowing reports of good treatment, along with a request to forward the letters to' the appropriate families. The POW letters made British security very suspicious, believing they were some ploy to determine where the bombs had fallen, and so all the leaflets were promptly confiscated. Such few as survive today are surprisingly valuable.

The V-1 was manufactured at various sites in the Reich, but the main production facility was the notorious underground SS slave-labour complex known as "Mittelwerk" at Nordhausen in the Harz Mountains. An estimated total of 24,000 V-1s were built in 1944, with as many as 10,000 built in 1945, though quantities tend to vary from source to source.

the Flying Bomb Blitz

The Allies landed on the Normandy beaches on 6 June, a week before the first launch of the V-1, but even as the fighting raged around the beachhead, the flying bomb attacks continued at a brisk pace from the launch sites in the Pas de Calais. The Allies had been expecting the flying bomb, which they codenamed DIVER, but the attacks still came as something of a shock and the defence was initially ineffectual. The British public reacted to the attacks with a combination of curiosity and fear as the little missiles buzzed overhead, sounding a little like "a Model-T Ford going up a hill" or "like a motor-bike with a two-stroke engine."

The V-1s were originally referred to in the press as "pilotless bombs" or "robot bombers", but Prime Minister Winston Churchill discouraged such language, as they made the weapons sound unstoppable. Eventually, the V-1s became known as "buzz bombs" from the engine sound, or particularly "doodlebugs", a name invented by New Zealander airmen who thought they sounded like a loud buzzing bug of their homeland.

Although the flying bombs were inaccurate, the Germans were launching enough of them to cause severe damage, and the random nature of the attacks was unnerving. Sometimes a flying bomb acted capriciously, shutting off its engine and then restarting it again, or even turning around and flying back the way it came. In fact, one made a U-turn shortly after launching and landed with a tremendous explosion near a command post that Hitler was scheduled to visit. Sometimes they seemed deadly accurate, leading some to believe they had a precision guidance system. One hit the headquarters of General Dwight Eisenhower, the Supreme Allied Commander.

The worst incident occurred on 20 June 1944, when one hit the Guard's Chapel attached to Wellington Barracks, not far from Buckingham Palace, killing 119 and wounding 141. Even when they caused no great loss of life, the flying bombs destroyed historic landmarks, as well as many homes. Churchill was enraged at the attacks, and urged that poison gases be dropped on German cities in retaliation. The RAF responded that such a measure would likely be less effective than the air attacks with high explosive and incendiary bombs already in progress.

German propaganda trumpeted that British citizens were streaming out of London at a rapid rate. In fact, youngsters were being evacuated to the countryside where they were generally out of harm's way, but at the same time workers were coming into the city to help repair the damage, and despite the terror of flying bombs falling out of the sky the city's inhabitants generally went about their business with characteristic English coolness. Lookouts were posted on top of factories to watch for flying bombs headed their way, and to sound an alarm when necessary so the workers could seek shelter. A popular department store announced that their basement was fitted as an air-raid shelter with a capacity of 1,500 people, and the establishment was equipped to give shoppers warning and all-clear signals.

Towards the End

Even though the launch sites were overrun, flying bombs continued to hit England, if in reduced numbers. Back in early July, a small number of flying bombs hit Manchester and Gloucester. Allied leadership was baffled as to where these attacks were coming from, since the range of the V-1 was roughly known, and there was no place near enough for the Germans to set up launch sites that could reach these targets.

As it turned out, the Germans were launching the flying bombs from specially modified Heinkel He-111 bombers, operating from airfields in the Netherlands. Work on this scheme predated the beginning of the flying bomb blitz, and involved removing the He-111's bomb racks and a fuel tank, and installing launching gear and provisions for carrying a V-1 nestled under the left wing. The modified bombers were given the designation "He-111H-22". This proved to be a risky business, since the flying bomb was very heavy and could be lethally tricky to launch. 1,200 V-1s were launched in this fashion, with the loss of 77 bombers. Twelve bombers were lost on two missions alone simply due to the premature detonation of the V-1's warhead after the He-111 left the runway.

Air launch was abandoned in mid-January 1945, due to the high attrition and the advance of Allied forces. However, the Germans were not quite done with this game, having developed a new version of the V-1 with a range of 400 kilometres (250 miles) by reducing the size of the warhead and increasing the size of the fuel tank. They launched about 275 of these long-range flying bombs against Britain from the Netherlands in March 1945. British defences were able to adjust to these last-gasp attacks, and the looming defeat of the Reich ended the campaign for good at the end of March. V-2 rocket attacks against England, which had begun in September 1944, slowly fizzled out as well.

During this last phase of the flying-bomb battle, the Germans also launched as many as 9,000 V-1s against continental European targets, particularly the Belgian port city of Antwerp and the neighboring city of Liege, in hopes of interrupting the flow of Allied supplies to their advancing armies. These attacks faded out in March as well. The Germans considered launching V-1s from the back of the Arado Ar-234 jet bomber, using an odd rack that pivoted the missile up away from the aircraft at launch. This project does not seem to have gone past the paper stage.

* One of the unusual side stories of the flying-bomb campaign was development of a piloted "suicide" V-1. The details of this weapon are obscure and contradictory.

In late 1943, the Germans had experimented with "manned missiles", in which pilots would point their aircraft at a ground target and bail out. Experiments along this line were performed with Focke-Wulf FW-190 and pulsejet-powered Messerschmitt Me-328 fighters, but proved unsuccessful. In May 1944, SS Hauptsturmfuehrer Otto Skorzeny, German's brilliant and ruthless commando leader, proposed using the V-1 for this job. Within two weeks, prototypes of variants of the manned weapon, known as "Reichenberg", were built, with designations "R-I" through "R-IV".

The R-I and R-II were glider trainers and lacked engines. The R-I was a single-seat trainer, while the R-II was a two-seat trainer with dual cockpits. The R-III was a two-seat powered trainer, while the R-IV was the operational weapon. About 175 R-IVs were built, and a group of volunteers was organized to fly them. The piloted flying bombs were to be launched by bombers of "KG-200", the Luftwaffe special operations unit.

In principle, the pilot was to aim the Reichenberg at a target and then bail out. In practice, the weapon lacked an ejection seat, and though provisions were made for escape, getting out of such an aircraft safely as it dived at high speed towards a target was problematic. The volunteer pilots who were to fly the bombs were known as "Selbstopfermaenner (Suicide Men)".

Unsurprisingly, many German officers did not like the scheme. In October 1944, a new commander named Werner Baumbach was appointed to KG-200, and he preferred Mistel to Reichenberg. The Germans had little enthusiasm for kamikaze missions. In fact, some sources say that the piloted V-1s were originally designed strictly as flight test machines, but it is difficult to fit that into the other parts of the story as they are recorded.

Along with the Reichenberg, another interesting dead-end adaptation of the V-1 was its use as an external fuel tank that could be towed behind an aircraft by a long pipe, with the pipe acting as both tow bar and fuel connection. The scheme was evaluated with an Ar-234 jet bomber, but never got beyond preliminary tests.

* The effectiveness of the V-1 is debatable. Detractors point out that the V-1 was far too inaccurate to be considered a militarily effective weapon. It was a weapon of mass terror that struck almost at random.

It did prove undeniably destructive. It inflicted almost 46,000 casualties, with over 5,000 people killed outright; destroyed 130,000 homes; and damaged 750,000 more. However, it had no real effect on the outcome of the war, and absorbed resources that might have been better used in the defence of the Reich. Others point out that the weapon was cheap to build and tied up a disproportionate amount of Allied resources. Though this was true, the Allies had the resources, and it is questionable that the V-1 prolonged the war by any significant length of time.

USAAF JB-2 / JB-1

Despite the V-1's limitations, the US military was very interested in it. In comparison to the bumbling American efforts in radio-controlled flying bombs such as the BQ weapons the German V-1 looked pretty good, and in July 1944 captured V-1 components were shipped to Wright-Patterson Field in Ohio for evaluation. Within three weeks, the USAAF and American industry had built their own V-1, which was designated the "Jet Bomb 2 (JB-2)" and more informally known as the "Thunderbug".

In August, the USAAF placed an order for 1,000 JB-2s with improved guidance systems: Ford built the pulsejet engine, designated "PJ-31"; Republic built the airframe, though that job would later be subcontracted to Willys-Overland; and other manufacturers built the control systems, launch rockets, launch frames, and remaining components. First successful launch of a JB-2 was on 5 June 1945.

The JB-2s were launched off a rail with a solid rocket booster, in contrast to the somewhat complicated steam catapult system used by the Germans. Two versions of JB-2s were built, one with a gyroscopic guidance system like that used with the V-1, and the other with a radio-radar guidance system. The USAAF also experimented with air-launching the JB-2. Most of the launches were from a B-17 bomber, though some were performed from B-24s and B-29s, but the USAAF decided it wasn't a good idea in any case. The Air Force was so enthusiastic with the results that they increased the order for JB-2s to 75,000 in January 1945. However, the end of the war in August dampened enthusiasm for the weapon, and the program was terminated in September of that year after over a thousand had been built.

The US Navy experimented with their own V-1 variant, the "KUW-1 (later LTV-N-2) Loon". After initial ground launch tests in 1946, a submarine, the USS CUSK was modified to launch the flying bombs. In February 1947, the CUSK successfully launched a Loon. The flying bomb was stored in a watertight hanger on the deck of the submarine, and assembled and launched by solid rocket boosters while the submarine was on the surface. It was tracked by radar and controlled by radio.

Another submarine, the USS CARBONERO, was used in the tests as a tracking and control platform. In 1948, a surface vessel, the USS NORTON SOUND, was modified for Loon launches, and performed four launches in 1949 and 1950. It doesn't appear that the Navy was ever serious about fielding the Loon but saw it as a useful test vehicle for improved naval cruise missiles.

The Soviets also built copies and derivatives of the V-1, which are discussed in a later chapter, and the French operated a target drone based on the V-1 and designated the "Arsenal 5.501" well into the 1950s, though it differed from the original design in having twin tailfins and radio control.

In the meantime, the Army had been working with Northrop to build another cruise missile, based on Northrop's famous flying wing concepts. The first model, the "JB-1", was a flying wing with a central fuselage housing twin GE turbojets. The missile carried two 900 kilogram (2,000 pound) bombs, built into pods on each side of the fuselage. Only two JB-1s were built, one as a piloted glider, designated the "MC-543 Bat", and the other with the GE engines. It proved to be underpowered and so the design was modified to accommodate a single Ford PJ-31 pulsejet. The new version was named the "JB-10", and ten were built. It was launched off a rail using solid rocket boosters.

The problem with the JB-10 was that Northrop had designed it to aircraft standards of quality, and it was simply too expensive for an expendable weapon. The project was cancelled in 1946. A wide range of other missiles were investigated in the JB program, including air-to-air and anti-radar weapons, but it appears little progress was made on these projects, and the cancellation of the JB-10 ended the JB program.

AJB-10 is shown undergoing tests at Eglin Field, Florida, near the end of World War 2

Both the United States and the Union of Soviet Socialist Republics (USSR) built jet-powered, nuclear-armed cruise missiles during the Cold War. The U.S. Air Force’s Northrop Snark, which became the biggest cruise missile ever placed in service when it was activated in 1958, could fly more than 10,000 km (6,000 mi). It was the first aircraft to use INS, and it also had a system that could lock on to stars to correct INS errors. It measured the exact position of Canopus, a visible star, to fix the missile’s position—just as human navigators take star sightings. An even larger missile, the North American Navaho, could cruise at 3,000 km/h (2,000 mph); it was tested but never entered service because the U.S. Air Force bought ballistic rockets instead. The smaller Martin Mace with a range of 2,300 km (1,400 mi) was the first missile with terrain-matching guidance when it went into service in 1959.