Fuse (explosives)
From Free net encyclopedia
- See fuse for the other meanings of the word.
In an explosive device, a fuse (or fuze) is the part of the device that causes it to function. In common usage, the word fuse is used indiscriminately, but when being specific (and in particular in a military context), fuse is used to mean a simple pyrotechnic detonating device, like the cord on a firecracker, while fuze is used to mean a more complicated device, such as a proximity fuze.
Fuse
Image:Fuse burning.jpg The simplest fuse is a length of combustible material which burns from the free end, through a small opening in the casing, and into the explosive charge, where it then ignites the explosive material. Fuses are still found in fireworks, model cannons, antique smoothbore firearms, some improvised explosive devices and many forms of pyrotechnics.
Fuse can be created using a wide variety of technologies.
- Small fireworks usually use a small length of visco fuse, a black powder cored fuse wrapped twice with string and waterproofed, or tissue coated with black powder and rolled to keep the black powder in the center.
- Larger fireworks, some commercial applications, and model cannons usually use a fuse which has a core of grains of black powder, wrapped in a sheath of cloth (usually cotton) fibers and then coated with a laquer, shellac, or more modern protective coating.
- Fuse for blasting (also known as safety fuse), is a larger diameter (typically 1/4 inch or 6.25mm) higher energy, more solidly protected cloth fiber wrapped black powder core fuse. Safety fuse fits into the opening at the end of a pyrotechnic or fuse-ignited blasting cap and is crimped into place. Pyrotechnic blasting caps are still the most common form of detonator used for commercial and military explosives worldwide.
- Some safety fuse has an outer layer of plastic around the cloth and black powder. This fuse can burn reliably underwater once lit.
Fuze
Image:Multiple fuzes.gif A fuze refers to a device used in munitions which is designed to detonate, or to set forces into action to detonate, the charge (or primer) under desired conditions.
Types of fuzes include:
- time fuzes detonate after a set time by using mechanical, electronic, or chemical timers.
- contact detonators or point detonating fuzes explode on impact.
- proximity fuzes cause a missile or other munition to explode when it comes within a certain distance of the target. Some proximity fuzes utilize radar, sonar, Infrared or television cameras.
- remote detonators use wires or radio waves to remotely command the explosive to function.
- altitude fuzes cause a bomb to explode at a certain altitude above sea level by means of a barometric altimeter
- historical example
Many weapons have fuze systems to ensure that they do not initiate (go off) before intended. In most cases the munition has to travel some distance before it can detonate. In other cases the bomb, mine or projectile has a fuze that prevents accidental initiation (for example, stopping turning of a small propellor so that the striker-pin cannot touch the detonator even if the weapon is dropped on the ground).
These sort of fuzes operate with aircraft weapons where the weapon may have to be dropped over friendly territory to allow a damaged aircraft to continue to fly. The crew can choose to jettison the weapons safe by dropping the devices with fuzes still attached, or drop them live by retaining the fuzes as the weapons leave the aircraft.
Aerial bombs and depth charges can be nose and tail fuzed using different detonator/initiator characteristics so that the crew can choose which effect (fuze) will suit target conditions that may not have been known before the flight. The arming-switch is set to one of safe, nose or tail at the crew's choice.
There also exist other fuzing systems.
See also
- fuze for ammunition
- Percussion cap
- The Manual of Crime: Explosives (contains instructions on how make some kinds of electronic fuses)de:Zünder