U.S. Artillery Fuzes, 1960's and After

FuzesWithout a proper fuze, artillery would be pretty much useless.
In the mid 19th century two basic types were in use, Time Delay and Impact. Time fuzes were combustion types, consisting of a burning fuse train, ignited upon firing. There were various designs, but all were only accurate to approximately the nearest 1/2 or 1/4 sec at best.

During the First World War, combustion time fuzes became more refined and early attempts at mechanical time devices were begun.
By WWII, the Mechanical Time Fuze was refined to a precision instrument and a new type, the Proximity Fuze, using radio technology was created.

Left to Right:  MTSQ-M564,  MT-M577,  VT-M532    

Today, different functional fuze types have been combined into the Multi Option Fuze for Artillery (MOFA). Microprocessor controlled, battery operated and programmable, the MOFA is an all-purpose artillery fuze for bursting munitions.

Features include:
 o Point Detonating Impact Super Quick (PDSQ)
 o Delay Time after target impact. (5 to 10ms)
 o Proximity Distance (9 to 10 m height of burst over normal terrain)
 o Time Delay, 0.5 sec to 199.9 sec in 0.1-sec increments, w/ PDSQ backup.
MTSQ and MT Fuzes
Modern MOFA
Modern MOFA Fuze (German)
Utilizes modern micro-chip technology and light weight materials, while still maintaining mechanically driven safety features.

Until the introduction of the MOFA, artillery fuzes were designed for specific functions and applications. There are many hundreds (thousands) of designs developed over the last century, making for a vast field of collecting.

Above left, is a sectioned Mechanical Time Super Quick M564 Fuze (Development model T197E2 ) produced during the late 1960's and early 70's for 105mm, 155mm and 8in. projectiles. It has a 2-100sec selectable delay with a Point Detonating back-up. There is a safety at the nose and a delay arming mechanism (DAM) at the bottom, which aligns the detonator with the booster only after the shell has traveled a safe distance (200 ft from the muzzle). The timer is powered by an internal main spring. The safety adapter (lower timer) is powered by centrifugal force generated by the spinning projectile. This fuze was likely manufactured by Hamilton Watch Company, who produced about 20 million of them at a cost of about $15.50 each (1970 dollars).  (Thanks Sam for the details!)

Next is the Mechanical Time M577 Fuze made in the 1980's for similar projectiles. It has an  improved time setting feature and modernized manufacturing design. However, this one uses centrifugal force to operate the main timing mechanism (Junghans centrifugal timer) instead of a wound main spring.

VT-M532 VT RF Tubes
Miniaturized RF Tubes
used inside the VT M532
(Shown at left)

Proximity Fuzes
Proximity fuze technology was developed during WWII, and two types were produced.
The first (British) was used for anti-aircraft rockets and relied on optics. A sensor was calibrated for broad daylight. As the missile approached the target the daylight shining into that sensor was reduced. When the sensor was shaded enough, an electrical circuit would close and detonate the warhead. While successful, it was useless when it came to shooting at night.
The second concept (U.S.) applied radio waves, using the same principle as Radar. The fuze transmits a signal which is reflected by the target and received by the fuze. This reflected signal increases in strength as distance is reduced. When the reflected signal intensity reaches a certain level, a triggering circuit electrically fires the detonator.
These early radio "VT" fuzes were large and fragile, using mechanical and vacuum tube components, but they were very successful in a number of applications and used to good effect.

With the advent of transistor technology in the 1950's electronics could be reduced in size, resulting in smaller more robust fuzes which could be applied to smaller munitions.

Variable Time Fuze M532
The VT-M532 was one of the first of a new generation of electronic hybrid proximity fuzes. The radio transmitter/detector is located inside the nose with amplifier/triggering circuits contained in the plug-in module below. A battery module with detonator and booster would screw in the bottom. The nose cone is made of plastic to allow radio signals to pass.
This dual purpose proximity fuze was developed in the 1960's for 81mm mortar use. It is selectable for Point Detonating or Proximity, designed to detonate the round between 3 and 30 ft above the target, depending on the terrain. The function is selected by rotating the top, moving an indicator to either Proximity or Point Detonating. Power is supplied by a thermal battery which is activated when fired.