The Wilmington morning star., 1945-10-13
SAFETY OF VT"
FUSE WASBUlLT
INTO RADIO SETS
BY FRANK CAREY

'- ooiehce Writer
| WASHINGTON, Oct. p 70
Safety for the men firing the "vr.
fuse and security against its -.
ture by the enemy had to be .b1;r
into'' the tiny radio set that rida .'
in the nose of a military missile
Scientists had to devise mecbou
isms to keep VT-eouipped shan
from going off during handlinq nr
before it got a safe distance from
the gun.
Also, they had to make the mic
sile blow itself up if it missed il,
target or failed to detonate bv ~
dio means. Otherwise it might fan
on our own troops - or behind
enemy positions, where its secret
would be discovered.
| Pre-firing safety was achieve.
by short-circuiting the fuses
electrical detonator cap.
The short circuit is maintained
by a wire which is capped at one
point. This gap is bridged by a
quantity of mercury in which the
wire is immersed.
When the projectile is shot from
the gun, the fast rotation of the
missile causes the mercury ia
leave the gap, thus breaking thu
short circuit. The detonator can
can now be activated when beams
from the fuses radio set are re.
Elected back by an enemy target.
This mechanism is used only in
missiles that rotate - such as
antiaircraft shells.
For missiles which do not rotate
- such as those fired from
mortars - a clockwork mechan.
ism. fixed for a delay of less than
second, causes the breaking Of
the short circuit.
Seh-destruction Of certain VT
missiles is done this way:
A metal reed switch is connect.
ed with the firing condenser. When
the shell is at rest, this switch is
closed, preventing the firing con.
denser from being charged electri.
cally.
| When the projectile Is fired, the
| rotation causes the reed switch to
open, allowing the firing condenser
to charge.
Now, if the projectile should
miss, or If the radio set should
fail, the shell begins to fall. Its
rotation decreases and the reed
switch begins to close again. 1t
strikes a pin which touches off the
explosive.
The self-destructiv mechanism is
employed most extensively in fuses
for .antiaircraft shells, since this
type is most likely to fall within
our own positions in case of miss.
The self destruction technique
has not been employed much in
missiles designed for long range
artillery fire or for anti-personnel
bombs. This is because the max
imum Regeneration effect S
achieved when the shell or bomb
is made to burst about 70 feet
above the terrain-the height at
which the radio beams SHOULD
WORK. The self-destroyer wouldn't
have time to work anyway.
Military men say it's possible
that some "duds" were taken by
the enemy, but at the end of the
war there was no evidence that
our foes had profited by a wind.
fall.
To prevent "duds" from being
picked up by the wrong people,
'VT' fuses were limited to naval
action for year and a half. buds
would fall harmlessly into the wa
ter.
First use from land was against
the buzz bombs in June, 1874 and
first use against ground troops and
equipment occurred in the Battle
of the Bulge
| incidentally, the Allies had tip
off the Germans were planning to
use robot bombs at least SIX
months before the first one was
launched against London.
Tests Of the effectiveness
Of VT" fuses against nock'up
representations of flying bombs
were conducted by American
scientists in January 1914 -- five
months before VT went into act
| ;o, a oo;oc% Tho h,,11orc