Sep 11

The Other Secret Weapon of World War II

Friday, September 11, 2015 9:16 AM

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USNI VT fuze.

Mockup VT proximity fuze made during its development in 1942. (Collection of the U.S. Naval Institute)

As a young officer, Admiral W.H. P. Blandy, USN, had a keen interest in gunnery. Writing for Proceedings in 1920 (“Director Fire a Century Ago”) and 1925 (“Possible Improvements in our Gunnery Training”), then–Lieutenant Commander Blandy understood well the history of fire control and what could be done to improve its effectiveness. Ever forward-thinking, Blandy noted elsewhere in 1925 of what a remarkable device a fuze that would detonate based on its proximity to the target would be.

It was not until 1940 that his initial proposition began to take shape, when the National Defense Research Committee took up the cause. Remarking on a memo that crossed his desk later in 1943, Admiral Blandy remarked about the process: “‘Here is something the Navy badly needs. Please go out and get it for us. . . . We don’t know how you are going to do it. If we did—we’d have done it!'”

So began the development of the VT proximity fuze, a project whose development War Department leaders would consider to be second only in importance to the development of the atomic bomb.

The principle of the device was rather simple: By equipping the shell fuze with a radio receiver, a signal could be transmitted from the fire-control radar system on board ship to precisely time the detonation for maximum effectiveness.

Of course there were many obstacles to overcome, not the least of which was developing electronic components rugged enough to withstand being fired from a gun. And then there was the problem of secrecy; any details that could give away the true nature of the project, any hint of what was being developed—anything to do with “influence” or “radio proximity”—had to kept absolutely cloaked. And so the very-apt designation of “VT” was chosen to name the fuze: “VT,” in this case, standing for “variable time,” an elegantly truthful designation if there ever was one.

As development on the fuze and its attendant Mk. 57 fire director system progressed, the need for a centralized laboratory became evident. The newly christened Applied Physics Laboratory of Johns Hopkins University took up the mantle of organization and management. Development progressed throughout 1942, with testing being done at the U.S. Naval Proving Ground in Dahlgren, Virginia, and at sites in Maryland, North Carolina, and New Mexico. The initial targets were clouds, and one test director recalled later being able to predict the closeness of rain by how soon the shells went off.

In January 1943, the fuzes were first used in combat. Just off Guadalcanal, the USS Helena (CL-50), which had been equipped with 500 rounds of the 5-inch VT projectiles in October 1942, came under attack by two Aichi D3A “Val” dive bombers. Within a minute and a half, both planes had been shot down. The antiaircraft control officer on board the Helena was convinced the shells had done their job.

Iowa-Missouri August 1945.

The U.S.S. Missouri (BB-63) (left) alongside her sister Iowa (BB-61) in August, 1945. Note the differences in fire-control radar systems visible on their masts. (U.S. Naval Institute Photo Archive)

Others were not so ready to adopt the new technology. The USS Missouri (BB-63) was equipped with the Mark 57 fire director and loaded with the new VT projectiles in 1944, and her arrival in the Pacific theater that December was met with not little skepticism and some outright hostility. A shooting competition over Ulithi Atoll between the Missouri and her sister Wisconsin (BB-64), which was not equipped with either the new fuses or fire director, quickly dispelled any doubts as to the effectiveness of the new system.

By war’s end, more than 22 million fuzes had been produced for the United States and Great Britain. They had proven their devastating effectiveness time and time again against such targets as aircraft, terrorizing V1 “Buzz Bombs,” and Axis armored units.

Addressing the team who developed the VT fuze after the war, Naval Bureau of Ordinance chief George F. Hussey remarked, “Few men in uniform who have been decorated for some individual act and no workers in a plant flying the coveted Army-Navy E have more right than you to recognition.” credit-n.ru
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