A “Wonder Weapon” Against Japan? The American V-1

Posted on Wed, August 19, 2020
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In earlier blogs in this series, I wrote about the exaggerated reputations of the “wonder weapons” that Nazi Germany deployed in the last year of World War II, and about the slave laborers the Nazis exploited and murdered to produce those weapons. The one with the most immediate impact was the V-1 cruise missile.  The Luftwaffe (German air force) launched 22,000 V-1 missiles, mostly against London and Antwerp, although many failed in flight or were shot down. These “doodlebugs” and “buzz bombs,” as Allied civilians and soldiers called them, caused a lot of destruction and terror, but the missile was not the war-changing weapon Nazi leaders hoped it would be. It did, however, impress the American military enough that it set out to copy it for use against Japan prior to an invasion. The result was an American V-1, which the U.S. Army Air Forces (USAAF) called the JB-2 and the U.S. Navy dubbed the Loon. A Loon is on display in the Boeing Aviation Hangar at our Steven F. Udvar-Hazy Center. 

Loon Missile

A U.S. Navy Loon at the Steven F. Udvar-Hazy Center.  (Smithsonian National Air and Space Museum, NASM 2013-02974).

Allied intelligence services had photographed the V-1 from the air and received crashed parts from resistance sources, but only when the campaign against London began on June 13, 1944, one week after D-Day, did it become possible to get a closer look. Several V-1s had landed reasonably intact when their cut-off devices failed to initiate a terminal dive on the target. Within three weeks, engineers and technicians at the USAAF’s primary technical center at Wright Field near Dayton, Ohio, had reverse-engineered the simple pulsejet engine, which is basically a tube with a flapper valve at the front, plus fuel injectors and a spark plug. The engine produced about 900 lbs. of thrust through rapid, intermittent combustion, leading to the deafening buzz that gave the missile one of its nicknames. Because the engine did not produce enough thrust at zero velocity to launch the device, it needed a boost. The Germans used steam catapults as their primary operational method. The U.S. decided to employ readily available, solid-fuel JATO (Jet-Assisted Take Off) rockets.

The JB-2 (Jet Bomb-2) was rushed into production in late 1944. (The JB-1 was a parallel missile of American design that the Army Air Forces quickly terminated as inferior.) Ford Motor Company made the engine, while Republic Aviation was to produce the airframe, but that corporation was so taxed with P-47 Thunderbolt manufacturing that it subcontracted the job to Jeep maker Willys-Overland. Visually, it is not easy to distinguish the JB-2 from a V-1. The wingspan is a little bigger, the pylon supporting the front of the engine is shaped a little differently, and the small, range-counting propeller sticks out a little farther. (The number of revolutions roughly measured the distance flown; a magnetic compass provided the heading, a barometer regulated the altitude, and an autopilot kept the missile flying steadily.)

A Republic-Ford JB-2 on display at Wright Field in 1946

A Republic-Ford JB-2 on display at Wright Field in 1946, (San Diego Air and Space Museum, 3920012).

On October 12, 1944, the first JB-2 was launched at Eglin Field in the Florida panhandle. Tests over the Gulf of Mexico continued throughout the fall and winter, including experiments in aircraft launching (the Luftwaffe fired some V-1s against England using Heinkel He 111 bombers). The Navy made its own plans for launching the missile (which it called the KGW-1, and later the LTV-N-2 Loon) from ships and landing craft. Initial plans were to deploy them against Germany as well as Japan, but that became moot as the European war came to its violent conclusion. In June 1945, USAAF Commanding General Henry “Hap” Arnold listed the JB-2 as his third priority, after the Boeing B-29 bomber and the Lockheed P-80 jet fighter, with the plan to barrage Japan with missiles prior to the invasions of first Kyushu, then Honshu. Arnold was among the select circle who knew about the atomic bomb, so it is interesting to see that he was not expecting that the war would end suddenly the way it did. It’s also a little hard to see why he wanted the JB-2 so urgently, given that B-29 firebombing was already reducing Japanese cities to ashes. Perhaps the psychological effect on the population was at the center of his expectation—even though British and Belgian morale did not collapse in similar circumstances.

A Loon Missile moments after launch from the US Navy submarine USS Cusk as part of Project DERBY

A Loon Missile moments after launch from the US Navy submarine USS Cusk as part of Project DERBY (launch #586), 29 June 1949. (Smithsonian National Air and Space Museum, NASM 7B19979).

After the war, the American V-1 became an important training device for the Navy and Air Force (which got its independence in 1947). Experimental launches in Florida and New Mexico, and off ships at sea, provided experience in working with missiles. On February 12, 1947, the Loon became the first submarine-launched missile when one was fired off the deck of the USS Cusk near California. The V-1 and its American copy were also the inspiration for many postwar experiments, as is visible in the line of Navy “Gorgons” hanging above “Rocket Row” on the north side of the McDonnell Space Hangar. The late 1940s and early 1950s saw the first wave of U.S. military enthusiasm for the cruise missile. At a time when accurate guidance for rocket-powered, intercontinental ballistic missiles appeared unlikely, the services bet heavily on V-1 descendants. The first nuclear-armed cruise missiles, the Air Force’s Matador and the Navy’s Regulus I, are in the Hangar too, not far from the Loon. For the evolution of the cruise missile in the United States, there is no better place to visit than the recently reopened Udvar-Hazy Center. I hope you get a chance to go.


Michael J. Neufeld is a senior curator in the Museum’s Space History Department and is responsible for the rockets and missiles collection and for Mercury and Gemini spacecraft. He has published widely on German and American rocket and space history.

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