The American V-1 Program 1944-1950

Beginning in 1942, Allied intelligence began a systematic analysis of the Fiesler Fi 103 flying bomb better known as the V-1. Analysis of crashed test articles combined with photoreconnaissance and intelligence collected by agents within occupied Europe led the United States in particular to restart its flying bomb programs in 1943 that had laid dormant for the most of the Second World War on account of what was felt to be beyond the current state of the art. In 1944, Northrop was contracted to begin development of the first US flying bomb, designated the JB-1. Running parallel to the Northrop effort was the reverse-engineering of the V-1 using 2,500 lbs of salvaged V-1 parts that had been provided by Great Britain. The parts arrived at Wright-Patterson Field in Dayton, Ohio, on 13 July 1944 and the US Army Air Forces directed the engineering staff there to build 13 copies of the V-1. Quite remarkably, the USAAF technical staff completed the first copy in just three weeks! To put the scope of the success of the Allied intelligence effort and the work the Wright-Patterson Field team into perspective, the first German V-1s struck Britain on 12-13 June 1944. By the end of the following month, the USAAF had its first copy of the V-1 and they had test fired the reverse-engineered pulse jet engine. A memo from the technical team responsible to General Henry Arnold, head of the USAAF, recommended mass production at the earliest opportunity- however, General Arnold and his advisors were well aware of the V-1's inaccuracy and despite reservations that production of an American V-1 would divert crucial wartime resources and manpower from battle-proven weapons, it was felt that if the guidance of the V-1 could be improved, an American version might be useful. 

The Republic-Ford JB-2 differed from the V-1 in minor details
(USAF/Wikipedia)

Republic Aviation was tasked with producing the American V-1 which was designated JB-2 with the first of the thirteen USAAF copies arriving on 8 September 1944 from Wright-Patterson Field. The USAAF ordered 1,000 JB-2s from Republic. The Ford Motor Company was tasked with producing the JB-2's pulse jet engine which was designated the PJ31. With Republic's resources nearly all committed to the production of the P-47 Thunderbolt, the company subcontracted the airframe assembly to Willys-Overland, the same company that built the Jeep. With Ford responsible for engine production, the Jack & Heintz Company of Cleveland which had been building aircraft electrical components and autopilots as a subcontractor was given responsibility for the JB-2's control system. Alloy Products of Wisconsin was given responsibility for the fuel tanks and pressure vessels used in the JB-2 while the Northrop was contracted for the JB-2's launch sled. The booster rockets that actually propelled the JB-2 off the ground were contracted to Monsanto. 

By the end of September 1944, the USAAF revised its initial order for 1,000 JB-2s to 1,000 JB-2s *per* month with a target goal to reach that rate by April 1945. The first JB-2 launch took place at Eglin Airfield in Florida on 12 October 1944- just three months had elapsed since start of the German V-1 campaign against London and the first American copy had made its first flight! Flight testing was also carried out at Wendover Field in Utah at the same time that the B-29 Superfortress unit that dropped the atomic bombs, the 509th Composite Group, was a tenant at Wendover training for their special mission. The flight tests didn't go too smoothy- by the first week of December, there were two successful flights out of ten launches. 

JB-2 air launch from a B-17 at Eglin Army Air Field in 1944
(USAF/Wikipedia)

Northrop's own flying bomb design, the JB-1, made its first launch in December 1944 but crashed after launch. (The JB-1 will be the subject of its own later article here at Tails Through Time.) With the the early failures of the JB-1 and problems with its jet powerplant, the USAAF decided to continue with the development of the Northrop design but production and operational priority went to the JB-2. Despite issues with accuracy in the flight tests at Eglin and Wendover, the USAAF leadership pushed for an increased production rate for the JB-2 to at least 3,000 per month. On 14 January 1945, General Arnold ordered another 75,000 JB-2s with the ability to launch 100 per day by September and 500 per day by January 1946 in anticipate of the invasion of Japan. On the next day, the JB-2 program got the same priority that was given to the B-29 Superfortress program. 

Despite the enthusiasm from the USAAF leadership, theater and operational commanders were skeptical of the JB-2. The generally poor European weather that was interfering with the strategic bombing campaign, however, offered perhaps some utility for the JB-2 as it wasn't dependent on clear weather- a view supported by Sir Trafford Leigh-Mallory, the head of the Royal Air Force and commander-in-chief of Allied air forces for the Normandy invasion as well as General Carl Spaatz, head of US Strategic Air Forces Europe. Spaatz, however, was a bit more measured in his support for the employment of the JB-2. He felt that it was more a harassment weapon that could be used when bad weather precluded a strategic bombing mission and outlined his planned use at 300 JB-2s per day only 10 days out of the month. But General Spaatz was very specific that operational employment of the JB-2 could not interfere with heavy bomber operations and he personally expressed concerns to General Arnold regarding the JB-2's cost-effectiveness given its inaccuracy. 

The JB-2 flight test program centered primarily on improving the weapon's accuracy. The first successful flights in the fall of 1944 showed an average error of eight miles at a range of just over 120 miles, not much better than what the Germans were averaging in their own V-1 campaign. The next step by the USAAF was to install radio guidance control in the JB-2. Using a radar beacon and remote control, it was thought the JB-2's accuracy could be improved. However, continued flight tests showed in 20 flight tests with the new guidance system, the JB-2's average error was no better than it was before with preset controls. Things did get better though- by war's end, the JB-2 with preset controls was averaging 5 miles error over a range of 150 miles and 1/4 mile error over a range of 100 miles with radio guidance. 

The biggest stumbling block to the operational deployment of the JB-2 in Europe in 1945, believe it or not, was logistical. The sheer numbers of JB-2s needed competed with other munitions production and it was estimated by some in the War Department that just transporting the JB-2 and its associated equipment to Europe would take up nearly 25% of Allied shipping capacity in the Atlantic. Brief consideration was given to moving JB-2 production to Europe, but there simply wasn't the production capacity anywhere else but the United States to produce the numbers of JB-2s planners envisioned using. 

With the end of the war in Europe, JB-2 production numbers remained in flux as planners debated what was needed for the planned invasion of Japan. By this point, however, the production and logistical concerns for the mass deployment of the JB-2 had exhausted the initial enthusiasm for the weapon. Production was halted initially at the end of January 1945 but then reinstated at a lower rate. By the time of the Japanese surrender, 1,385 JB-2s had been built when production was terminated.

Concurrent with the USAAF testing, the US Navy worked on a navalized version of the JB-2 that would have been launched from specially-modified LSTs and escort carriers during the invasion of Japan. Fifty-one JB-2s were requested by the Navy for its own testing program in September 1944 when production was launched. While airborne launches from B-17 Flying Fortresses were done during testing at Eglin Field, the Navy planned to launch JB-2s from Consolidated PB4Y Privateers as well. Navy planners, however, didn't expect operational capability with the JB-2 (which was called the Loon by the Navy) until August or September 1946. The first Navy Loon launch was on 7 January 1946 with the Secretary of the Navy approving the conversion of two submarines for Loon operations in March 1946. Conversion of the USS Cusk (SS-348) began in January 1947. The Cusk entered the history books on 18 February 1947 as the world's first missile submarine when it made its first Loon launch...which ended in failure after only 3.5 miles of flight. The Cusk finally had its first successful launch on 7 March 1947 after five tries. Submarine launch had become the Navy's focus for the Loon program with the USS Carbonero (SS-337) also modified for the program and by 1949 finally carried out a firing from a surface ship, the test ship USS Norton Sound. In March 1950, the Navy terminated in the Loon in favor of the more promising Regulus cruise missile. 

The USS Cusk fires a JB-2 Loon
(US Navy/Wikipedia)

With the US Air Force becoming independent in 1947, the JB-2 program was reactivated in March 1948 at Holloman AFB in New Mexico as part of a program for the development of missile guidance systems and seeker technology. Work using the JB-2 benefitted the later Matador cruise missile program with the JB-2 program winding down by 1949 with test airframes successfully being flown remotely and skid landed for recovery. A joint effort with Eglin AFB also used the JB-2 as a target drone for the development of gunsights. Interestingly "Flakzielgerät 76" was the German cover name for the V-1 during its development which loosely translates as anti-aircraft target device.

Further reading:

British Defenses Against the Summer 1944 V-1 Bombardment
Regulus: The US Navy's First Operational Nuclear Missile
CHECK SIX: Ships Damaged or Sunk by the Yokosuka MXY7 Ohka

Sources: The Evolution of the Cruise Missile: Comprehensive History from the V-1 and V-2 to the Tomahawk and Snark by Kenneth P. Werrell. Air University Press/USAF, 1983, pp 79-85. V-1 Flying Bomb 1942-1952: Hitler's Infamous Doodlebug (New Vanguard No. 106) by Steven J. Zaloga. Osprey Publishing, 2005, pp 39-41.

British Defenses Against the Summer 1944 V-1 Bombardment

Cutaway view of the Fiesler Fi 103, or V-1 "Buzz Bomb"

Within a week of the Allied landings on Normandy on 6 June 1944, the Germans initiated a new form of bombardment against London, launching ten of Hitler's "Revenge Weapon No.1" or Vergeltungswaffe 1- V-1 for short. Of the V-1s launched in the early morning darkness of 13 June, six suffered failures that prevented them from even reaching the English coast from launch sites at Pas de Calais. Four bombs made it into British airspace, three of them hit in open land causing no casualties. One of those four V-1s, though, hit Bethnal Green, 2 miles from the famous Tower Bridge (which was used as the nominal aiming point) where it killed six people and injured nine more. British intelligence had predicted history's first cruise missile bombardment for a year, but the opening salvoes were far smaller than what was feared. It took three days to resume the launches and by 16 June 244 V-1s had been fired at the British capital. Of those missiles, 153 crossed into British airspace and of those V-1s, 73 hit the London area causing widespread damage and civilian casualties. 

German launcher crew prepare a V-1 on its firing ramp in France

In the three day lull following the first attack, the Royal Air Force and British Army swiftly deployed its defenses to southeast England. The first line of defense consisted of nine squadrons of Supermarine Spitfire and Hawker Tempest fighters as well as two squadrons of De Havilland Mosquito night fighters. The aircraft three lines of standing patrols, the first line 20 miles off the coast, the second line at the coast, and the third line 15 miles inland. Behind the fighter patrols came the gun zone made up of 192 heavy caliber AA guns and nearly 200 light-caliber guns in an area 20 miles deep. If a fighter pursued a V-1 into the gun zone, gunners were ordered to hold their fire to allow the fighter to complete its pursuit. Behind the gun zone on the southeast suburbs of London was the balloon zone made up of 480 barrage balloons. Over a quarter million mothers and children were evacuated out of London itself during the bombardment. Up to the end of June 1944, an average of 153 V-1s were fired at London. One-third failed or were shot down before crossing the English coast. Another one-third crashed or were shot down over southeastern England before reaching London. But that left a significant amount that managed to hit the London area. 

By mid-July, the defenses were revised based on the experience so far. This time each defensive measure was given a predefined zone for unrestricted engagement of any flying targets. The British Army's AA gun batteries were increased to 412 heavy guns and nearly 600 light guns in a 65-mile long strip along the coast that allowed the gun-laying radars of the batteries a clear view over the English Channel. Fighter pilots were prohibited from crossing the new gun zone, knowing that the gun batteries had unrestricted rules of engagement. The fighter zones were now split into two, with an outer zone over the English Channel that stopped five miles from the coast where the gun zone began. The inner zone began at the rear of the gun zone along the coast and extended back to the barrage balloon zone in London. In less than a month the number of barrage balloons increased to over 2,000. With the new defensive layout, over one-half of incoming V-1s were stopped from reaching the capital. 2 August would be the heaviest bombardment day, with 316 V-1s launched from 38 launchers in Pas de Calais. Of that number, 107 would impact in London. On that day, the nominal aiming point for the V-1 batteries in France, the Tower Bridge, took a direct hit from a V-1. 

A Spitfire pursues a V-1 at treetop height

By early August, the first Gloster Meteor jet fighter units were becoming operational and were tasked with V-1 interception. However, there were three developments that would vastly improve the British defenses, all technological wizardry courtesy of the United States. First was the SCR-584 gun laying radar that was the state of the art in 1940s radar technology and could lock onto targets instead of having to be manually directed by operators. A new device called the the Number 10 Predictor was the second device, it could exploit the improved fidelity from the SCR-584 to direct the AA fire more accurately. And the third bit of wizardry would also save many US Navy carriers and warships in the Pacific- proximity-fuzed AA shells that no longer needed a direct hit to bring down a target. With these three advances, the average V-1 engagement by a British Army gun battery only used a mere 156 rounds to bring down a V-1. 

The last V-1 launched from Pas de Calais came on 1 September, by which point the launch sites were all overrun by British Army units on the breakout from the Normandy beaches. From that point on, the V-1s that hit London were delivered by air-launching which was less effective and more prone to interception. During the first phase of the bombardment from June to September 1944, until the British defenses received new radars and proximity-fuzed AA shells, the most effective defense was actually the Allied air attacks on the French rail system. V-1 launch sites often had to wait days before receiving new missiles to fire due to attacks on supply trains and the rail network itself. Throughout this first V-1 bombardment phase, the launchers at Pas de Calais never launched V-1s at their intended capacity. 

The V-1's magnetic compass in the nose was enclosed in a wooden sphere

By far the most interesting defense that nearly got fielded in the summer of 1944 also came from the United States. Dr. Don Hare and his team at the Airborne Instruments Laboratory in New York were working on radio countermeasures systems when they were asked by the US government to assist in developing a counter to the V-1 attacks on London. Since the V-1 required no outside cues, it was invulnerable to jamming. Its direction guidance came via a magnetic compass in the nose that cued the master gyroscope that controlled the rudder. As the V-1 had to be simple to produce, it lacked any ailerons and its straight wing lacked any dihedral to provide stability. RAF pilots had already discovered a V-1 could be thrown off course and downed by forcing the bomb into a steep bank by tipping one wing. Dr. Hare's team reasoned that if a suitably strong magnetic field could be created, the magnetic compass could be tricked into cueing the master gyroscope to put the V-1 into a tight turn, thereby downing it. The American team's idea was to use existing railway lines that formed a loop around London 60 miles in circumference as a giant magnetic loop. By connecting specific rail lines in a giant circuit, it would take 1,000 amps of DC power to create a magnetic field over London that could confuse the V-1's autopilot. It was determined that 20 to 30 megawatts were needed which was within the capacity of a large commercial power station. Design work began on the needed equipment, but the "Mightiest Magnet" program ended when the launch sites in Pas de Calais were overrun by Allied forces. 

Source: International Air Power Review, Volume 27, Winter 2010/11. "Pioneers & Prototypes- Vergeltungswaffe 1- Adolf Hitler's revenge weapon" by Dr. Alfred Price and P.G. Cooksley, p150-159.