Signal Corps Message November 23, 1945  Page 1 & 6

Proximity Fuse Largely Due To Evans Lab Men The war's second top secret, the proximity fuse, had a major por tion 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 labor atories, Squier, Evans, and Coles, revealed hundreds of war secrets on the press tour and it was dur ing this tour that the Signal Corps' part in the development of the proximity fuse was discussed. Sec ond 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 detona-
tion of the explosive charge when
they bounce back from enemy air-
craft, ground objects or the earth
itself.

   Such an explosion, a dis-
tance above the earth, has a
Devastating effect.  No foxhole,
Wall, or river bank can pro-
tect 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 re-
sponsibility for the development
and procurement of the non-rotat-
ing type fuse for use in rockets
and aerial bombs.
     The basic design originated with
The Bureau of Standards in Wash-
ington, D.C., after which the Sig-
nal Corps took over the develop-
ment of the non-rotating fuse.  En-
gineers from Evans Signal Lab
nursed the project through its
manufacture, investigating and
overcoming all obstacles that
turned up in the war plants en-
gaged in the project throughout
the country.

     Tiny ‘Power Plant’ Devised

     A major hurdle in Army devel-
opment of the fuses was the prob-
lem of supplying electric power for
the minute radio.  This was ten-
tatively solved by development of
a tiny dry-cell battery which, al-
though no larger that 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 prov-
ing ground tests, but Signal
Corps engineers realized it
Would be undependable in com-
Bat because the batteries
Would fail in the extreme cold
Of high altitudes at which mod-
ern bombers fly.  The limited
“shelf-life” of the batteries
Was another objection, for they
Soon lose potency in warm cli-
mates.
     Under Signal Corps supervision,
A development program was estab-
lished at the National Bureau of
Standards in Washington to per-
fect 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 rev-
olutions 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 form
Other nearby planes, the connec-
tion between the fuse and the de-
tonator 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 arm-
ing of the projectile.

Page updated March 22, 2008  created March 22, 2008,