Projectile

A projectile is any object propelled through space by the exertion of a force, which ceases after launch. In a general sense, even a football or baseball may be considered a projectile. It can cause damage (injury, property damage) to a person, animal or object it hits, depending on factors including size, shape, speed and hardness. Accordingly, in practice most projectiles are designed as weapons.

Motive force

Arrows, darts, spears, and similar weapons are fired using pure mechanical force applied by another solid object; apart from throwing without tools, mechanisms include the catapult, slingshot, and bow.

Other weapons use the compression or expansion of gases as their motive force.
Blowguns and pneumatic rifles use compressed gases, while most other guns and firearms utilize expanding gases liberated by sudden chemical reactions. Light gas guns use a combination of these mechanisms.

Railguns utilize electromagnetic fields to provide a constant acceleration along the entire length of the device, greatly increasing the muzzle velocity.

Some projectiles provide propulsion during (part of) the flight by means of a rocket engine or jet engine. In military terminology, a rocket is unguided, while a missile is guided. Note the two meanings of "rocket": an ICBM is a missile with rocket engines.

Non-kinetic effects

Many projectiles, e.g. shells, contain an explosive charge. With or without explosive charge a projectile can be designed to cause special damage, e.g. fire (see also early thermal weapons), or poisoning (see also arrow poison).

Kinetic projectiles

Projectiles which do "not" contain an explosive charge are termed "kinetic projectile", "kinetic energy weapon", "kinetic warhead" or "kinetic penetrator". Classic kinetic energy weapons are blunt projectiles such as rocks and round shot,pointed ones such as arrows, and somewhat pointed ones such as bullets. Among projectiles which do not contain explosives are also railguns, coilguns, mass drivers, and kinetic energy penetrators. All of these weapons work by attaining a high muzzle velocity (hypervelocity), and collide with their objective, releasing kinetic energy.

Some kinetic weapons for targeting objects in spaceflight are anti-satellite weapons and anti-ballistic missiles. Since they need to attain a high velocity anyway, they can destroy their target with their released kinetic energy alone; explosives are not necessary. Compare the energy of TNT, 4.6 MJ/kg, to the energy of a kinetic kill vehicle with a closing speed of 10 km/s, which is 50 MJ/kg. This saves costly weight and there is no detonation to be precisely timed. This method, however, requires direct contact with the target, which requires a more accurate trajectory.

With regard to anti-missile weapons, the Arrow missile and MIM-104 Patriot have explosives, but the Kinetic Energy Interceptor (KEI), Lightweight Exo-Atmospheric Projectile (LEAP, see RIM-161 Standard Missile 3), and THAAD being developed do not (see Missile Defense Agency).

See also Hypervelocity terminal ballistics, Exoatmospheric Kill Vehicle (EKV).

A kinetic projectile can also be dropped from aircraft. This is applied by replacing the explosives of a regular bomb e.g. by concrete, for a precision hit with less collateral damage. A typical bomb has a mass of 900 kg and a speed of impact of 800 km/h (220 m/s). It is also applied for training the act of dropping a bomb with explosives. [http://www.fas.org/news/iraq/1999/10/991007-iraq.htm] This method has been used in Operation Iraqi Freedom and the subsequent military operations in Iraq by mating concrete-filled training bombs with JDAM GPS guidance kits, to attack vehicles and other relatively "soft" targets located too close to civilian structures for the use of conventional high explosive bombs.

A kinetic bombardment may involve a projectile dropped from Earth orbit.

A hypothetical kinetic weapon that travels at a significant fraction of the speed of light, usually found in science fiction, is termed a relativistic kill vehicle (RKV).

Wired projectiles

Some projectiles stay connected by a cable to the launch equipment after launching it:
*for guidance: wire-guided missile (range up to of 4000 meters)
*to administer an electric shock, as in the case of a Taser (range up to 10.6 meters); two projectiles are shot simultaneously, each with a cable.

Typical projectile speeds

Miscellaneous

Ballistics analyze the projectile trajectory, the forces acting upon the projectile, and the impact that a projectile has on a target. A guided missile is not called a projectile.

An explosion, whether or not by a weapon, causes the debris to act as multiple high velocity projectiles. An explosive weapon, or device may also be designed to produce many high velocity projectiles by the break-up of its casing, these are correctly termed fragments.

The term projectile also refers to weapons or any other objects thrown, shot or otherwise directed to enemies in video games or computer games.

Projectile is also the name of an annual anarchist film festival based in Newcastle UK * [http://www.projectile.org.uk]

ee also

*
** Arrow
** Dart
** Spear
** Torpedo
** Missile
* Atlatl
* Gunpowder
* Impact depth
* Trajectory of a projectile
* Range of a projectile
* Space debris
* Ballistics
* Kinetic bombardment

External links

* [http://www.physics-lab.net/applets/projectile-motion Projectile Motion Applet]