William Sterling Parsons - Proximity Fuze

Proximity Fuze

Parsons was posted back to Dahlgren in September 1939 as experimental officer. The atmosphere had changed considerably. In June 1940, President Franklin D. Roosevelt approved the creation of the National Defense Research Committee (NDRC), under the direction of Vannevar Bush. Richard C. Tolman, dean of the graduate school at Caltech was given responsibility for the NDRC's Armor and Ordnance Division. Tolman met with Parsons and Thompson in July 1940, and discussed their needs. Within the Navy, too, there was a change of attitude, with Captain William H. P. (Spike) Blandy as the head of BuOrd's Research Desk. Blandy welcomed the assistance of NDRC scientists in improving and developing weapons.

In September 1940, Parsons and Merle Tuve of NDRC began work on a new concept. Shooting down an aircraft with an anti-aircraft gun was a difficult proposition. As a shell had to hit a speeding aircraft at an uncertain altitude, the only hope seemed to be to fill the sky with a multitude of ammunition. However a direct hit was not actually required; an aircraft might be destroyed or critically damaged by a shell detonating nearby. With this in mind, anti-aircraft gunners used time fuzes to increase the possibility of damage. The question then arose as to whether radar could be used to create an explosion in the proximity of an aircraft. Tuve's first suggestion was to have an aircraft drop a radar-controlled bomb on a bomber formation. Parsons saw that while this was technically feasible, it was tactically problematic. The ideal would be a proximity fuze inside an artillery shell, but there were numerous technical difficulties with this. The radar set had to be made small enough to fit inside a shell, and its glass vacuum tubes had to first withstand the 20,000 g force of being fired from a gun, and then 500 rotations per second in flight. A special Section T of NDRC was created, chaired by Tuve, with Parsons as special assistant to Bush and liaison between NDRC and BuOrd.

On 29 January 1942, Parsons reported to Blandy that a batch of fifty proximity fuzes from the pilot production plant had been test fired, and 26 of them had exploded correctly. Blandy therefore ordered that full-scale production begin. In April 1942, Bush, now the Director of the Office of Scientific Research and Development (OSRD), placed the project directly under OSRD. The research effort remained under Tuve but moved to the Johns Hopkins University's Applied Physics Laboratory (APL), where Parsons was BuOrd's representative. In August 1942, a live firing test was conducted with the newly commissioned cruiser USS Cleveland. Three pilotless drones were shot down in succession.

Parsons had the new proximity fuzes, now known as VT (variable time) fuze, Mark 32, flown to the Mare Island Navy Yard, where they were mated with 5"/38 caliber gun rounds. Some 5,000 of them were then shipped to the South Pacific. Parsons flew there himself, where he met with Admiral William F. Halsey at his headquarters in Noumea. He arranged for Parsons to take VT fuzes out with him on the USS Helena. On 6 January 1943, Helena was part of a cruiser force that bombarded Munda in the Solomon Islands. On the return trip, the cruisers were attacked by four Aichi D3A (Val) dive bombers. Helena fired at one with a VT fuze. It exploded close to the aircraft, which crashed into the sea.

To preserve the secret of the weapon, its use was initially permitted only over water, where a dud round could not fall into enemy hands. However in late 1943, the Army obtained permission for it to be used over land. They proved particularly effective against the V-1 flying bomb over England, and later Antwerp in 1944. A version was also developed that could be used with howitzers against ground targets. In response to the German Ardennes Offensive in December 1944, its use was finally authorized, and with deadly effect. By the end of 1944, VT fuzes were coming off the production lines at the rate of 40,000 per day.