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; conversely, 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.

Kinetic projectiles

Some projectiles do not contain an explosive charge (such as shells). They are termed kinetic projectile, kinetic energy weapon or kinetic penetrator. The classic kinetic energy weapon is the bullet. Among projectiles which do not contain explosives are railguns, coilguns, mass drivers, and kinetic energy penetrators, in addition to smaller weapons such as bullets. 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 done at the right time. This method, however, requires direct contact with the target, which requires more accuracy. With regard to anti-missile weapons, the Arrow missile and MIM-104 Patriot have explosives, but the KEI, LEAP, 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. [1] 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).

Typical projectile speeds

See also: Orders of magnitude (speed) and Muzzle velocity

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.

See also

• Category:Projectiles
  • Arrow
  • Dart
  • Spear
  • Torpedo
  • Missile
• Atlatl
• Gunpowder
• Impact depth
• Trajectory of a projectile
• Range of a projectile
• Collision (physical attack)
• Space debris
• Ballistics
• Kinetic bombardment

External links

• Projectile Motion Applet