Time bomb
From Wikipedia, the free encyclopedia
A time bomb is usually an improvised explosive device comprised of a power source, often a battery, detonator, explosive charge, and timer, which substitutes for a fuse or trigger. Depending upon the design, the bomb can be set to detonate any time between a few minutes and several days after it has been secreted within the target area; also, a fake fuse, which serves no actual purpose in the bomb, can be implanted as a failsafe in case of discovery; the discoverer, thinking that the bomb is harmless as the fuse is not lit, may carry the bomb on their person to report it to authorities, unaware that it will still explode. The delay allows the person placing the bomb:
- to move away from the blast radius to avoid hurting themselves
- to move away to be more difficult to be identified as the planter of the time bomb
- to place the device when nobody is present, and set it to detonate when victims are expected to be around.
Compare with devices where the delay is shorter (eg. 4–5 seconds for a hand grenade); or other methods of triggering, such as by remote control, or some kind of sensor, such as air pressure (altitude/barometric), radar, vibration or contact (landmine or trip-wire mine), and the case of a suicide attack, where no delay is needed.
|
[edit] Construction and usage
[edit] Components
[edit] Explosive charge
The explosive charge is the main component of any bomb, and makes up most of the size and weight of them. It is the damaging element of the bomb (along with any fragments or shrapnel the deflagration might produce with neighboring objects). Most explosives cannot ignite with simple sparks; they require a source of heat high enough to start the combustion (or chain reaction in case of nuclear explosives), which makes them easy and safe to store and handle.
[edit] Timer
Timers have varied through the years. Early time bombs use wind-up alarm clocks, which trigger the bomb when the alarm rings at the set time. Modern timers are electronic; on the low-tech end of the scale, cheap wrist watches are used and the bombs are triggered when the alarm beeps at the set time, and, on the high-tech end, sophisticated programmable devices such as dismounted computer laptops are used and the bombs can be triggered at a relative or absolute time (see Programming the timer below).
[edit] Detonator
The detonator is the source of heat that will start the combustion (or chain reaction in case of nuclear explosives). It is itself an explosive, with a lower ignition point than the main explosive charge. The detonator itself is ignited by another even lower source of heat, usually an electrical spark. A well-made bomb has a detonator just large enough to ignite the main explosive charge, but small enough to minimize the bomb's total size and weight.
[edit] Power source
Almost all power sources are electrical batteries. They supply power to spark the detonator, and, in case of electronic timers, supply power to the timers as well. A well-made bomb has a battery just strong enough to spark the detonator, but small enough to minimize the bomb's total size and weight.
[edit] Assembly and activation
[edit] Connecting the wires
Explosive charges can be grouped in one single bundle (to maximize the explosive damage) or grouped in several ones spread across an area (to demolish a building, for example). Each explosive bundle (whether single or multiple) has a detonator, and two wires link from each detonator to the timer and the power source. Another wire links the power source to the timer. Extra care must be taken when the detonator is being connected to the power source; if a short circuit happens, the detonator might be sparked prematurely and the bomb blows up in the bombmaker's hands.
[edit] Bundling the components
In a typical, compact time bomb, the detonator is placed in the center or on top of the explosive charge. The timer and power source are placed on top or to the side of them. The components are then wired and taped together, usually with electrical tape or any other strong tape. In the case of multiple explosive bundles, each bundle has its explosive charge and detonator taped together first, then each bundle is placed at its designated location, and, when all bundles are placed, they are wired together to the timer and power source.
In the case of a bomb concealed inside a container (briefcase, box, bag, etc), the components are arranged and attached in the shape of the container before being placed inside it.
[edit] Programming the timer
Old wind-up alarm clocks and wrist watches are set to explode when the currently displayed time reaches a certain set time. It is usually to set to an exact "xx hours and yy minutes" time, and are mostly used to destroy one or many targets at a specific time, such as a train passing at a station at the same time everyday. They are used when a target's passage at a certain point is known, regular and predictable.
Bombs with modern timers are more flexible and easier (more intuitive) to program. They can be set to explode "yy minutes and zz seconds" from any given time (usually the current time). They are mostly used in an improvized way, without knowing or being capable to predict a target's passage, or to destroy non-moving targets such as parked vehicles and buildings. They can be compared to grenades, but with much more explosive force.
Of course, the time between the bomb's programming and the bomb's explosion must be long enough to allow the bomb planter to walk away from the blast site before it explodes, preventing injury to himself.
[edit] Planting the bomb
Open bombs are placed directly on the target, or around it if the target is very large. They can be placed on the ground or on a wall or side of the target. When the timer is set, the bomb planter walk away from the bomb to a cover (a location which protects him from the bomb's blast) and waits for the bomb to explode before proceeding his course.
Concealed bombs are carried with their container (briefcase, box, bag, etc) to the blast location, and dropped silently next to a more-or-less inconspicous object such as a bench, a table or a cart. Most passer-bys will not notice the container, and those who see it will most likely walk by without picking it up, thiking that the next person who passes by will bring it to the lost and found.
[edit] When the timer reaches the programmed time
When the timer's alarm rings or countdown reaches zero, an electrical circuit is closed and power is fed to the detonator(s), igniting them and causing the bomb to explode. The timer, power source and wires are destroyed (vaporized) in the explosion, but there are some cases where some pieces remained intact after the blast, providing clues to forensic investigators.
[edit] Time bomb defusal
Time bombs are very difficult to defuse if they are well-made. Bomb defusers face not only the stress of time running out, but also the complexity of the electronic circuits and possibility of additional timer or power backups. Cutting a wrong wire may cause the countdown to accelerate or trigger an immediate explosion. Sometimes a special algorithm might be triggered, such as one causing the countdown to stop momentarily then resume several seconds later, fooling the bomb defuser that the bomb has been defused, lowering his guard.
Whatever method is used, whatever wire is cut, as long at the end no electricity from the power source can reach and spark the detonator, the bomb can no longer explode and is considered neutralized.
[edit] In popular culture
Time bombs are very common in action/thriller TV series, cartoons and films, where heroes often escape the blast area or defuse the bombs at the very last second (often performing a spectacular stunt).
Such TV series include:
- Knight Rider (1982-1986)
- MacGyver (1985-1992)
Notable films of recent times include:
- Die Hard: With a Vengeance (1995)
- The Peacemaker (1997)
- Battle Royale and Battle Royale 2:Requiem
- New Police Story
Classic films include:
- James Bond: Goldfinger (1964)
They are also the subject of computer and video games, where the player must plant a time bomb or defuse it, depending on which faction he belongs to in that game.
Such games include:
- Counter-Strike (1999-present)
- Sonic Adventure 2 (2001)
- Metal Gear Solid 2: Sons of Liberty (2002)
- Wolfenstein: Enemy Territory (2003)
Musical references include:
- Time Bomb (song) (1995)
- Time Bomb (song) (1996)
The explosives most often used in those works of fiction are C4 and dynamite, though other explosives such as gasoline & fertilizer mixtures, TNT and nuclear explosives are also common.
The stereotypical electronic time bomb includes 2 important wires, one red and one blue (or sometimes green instead of blue). Cutting one wire will accelerate the countdown and detonate the bomb, while cutting the other will stop the countdown and prevent the bomb from detonating. In all cases and scenarios, cutting the red wire stops the countdown, contrary to the popular belief that cutting that red wire will detonate the bomb prematurely (since the color red is commonly associated with danger, restriction and avoidance).[citation needed]
[edit] See also
[edit] References
[edit] External links
Guide which tells how to build timing devices:
