Signal Corps Message
November 23, 1945

Page 1, cont Page 6.

Proximity Fuse Largely

Due To Evans Lab Men

    The war's second top secret, the proximity fuse, had a major portion of its development take place
at the Evans Signal Laboratory, it was revealed during the day-long tour of the Fort Monmouth labor-
atories by the press Thursday, November 15th. The three laboratories, Squier, Evans, and Coles,
revealed hundreds of war secrets on the press tour and it was during this tour that the Signal Corps'
part in the development of the proximity fuse was discussed. Second only to the atomic bomb, the
proximity fuse remained a top-secret until the last day of the war.

     The fuse is a very small but incredibly rugged radio transmit-
                      ( Cont. on Page 6.)

Proximity Fuse 'Born' Here In Part
World's Second Top Secret Developed By Signal Lab Personnel

                      (Continued from Page One)
ter and receiver, the size of a man's fist. Installed in an aerial bomb, high frequency radio waves are sent
out which cause the detonation of the explosive charge when they bounce back from enemy aircraft, ground
objects or the earth itself.

     Such an explosion,
a distance above the earth,
has a devastating effect.
No foxhole, wall, or river bank
can protect men or equipment.

     There are two types of fuses. To the Navy was assigned the task of developing the rotating type fuse for
use in the huge naval rifles. To the Army went the responsibility for the development and procurement of the
non-rotating type fuse for use in rockets and aerial bombs.

     The basic design originated with the Bureau of Standards in Washington, D. C., after which the Signal Corps
took over the development of the non-rotating fuse. Engineers from Evans Signal Lab nursed the project
through its manufacture, investigating and overcoming all obstacles that turned up in the war plants engaged
in the project throughout the country.

Tiny 'Power Plant' Devised

     A major hurdle in Army development of the fuses was the problem of supplying electric power for the
minute radio. This was tentatively solved by development of a tiny dry-cell battery which, although no larger
than the cap of a fountain pen, supplied adequate voltage for the few seconds it had to function.

     This power source worked well in laboratory and proving ground tests,
but Signal Corps engineers realized it would be undependable in combat
because the batteries would fail in the extreme cold of high altitudes at which
modern bombers fly. The limited "shelf-life" of the batteries' was another
objection, for they soon lose potency in warm climates.

     Under Signal Corps supervision, a development program was established at the National Bureau of
Standards in Washington to perfect a generator to replace the batteries. A model was completed in late 1943,
utilizing a propeller in the nose of the projectile as a windmill to drive a tiny generator. Whirling at a rate of
100,000 revolutions per minute -50 times faster than the spin of an airplane propeller — the windmill supplies
sufficient power to the generator to create a continuous radiation of radio waves from the bomb or projectile.

     To prevent the proximity fuse from detonating the explosive upon receipt of wave echoes from the aircraft
which launched it or from other nearby planes, the connection between the fuse and the detonator is left open
until after the projectile has been launched. The first few spins of the windmill turn on a worm gear which
closes the connection and completes the arming of the projectile.

Page updated August 15, 2007 page created August 15, 2007

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Signal Corps Message November 23, 1945

Signal Corps Message
November 23, 1945