Projectile

From Wikipedia, the free encyclopedia

A projectile is any object propelled through space by the application of a force. In a general sense, even a football or baseball may be considered a projectile, but in practice most projectiles are designed as weapons.

1 Motive force
2 Kinetic projectiles
3 Typical projectile speeds
4 Miscellaneous
5 See also

[edit] 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.

[edit] 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, but on the other hand it requires a more accurate hit.

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).

A kinetic projectile can 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 e.g. 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. For a fictional kinetic weapon, see Relativistic kill vehicle.

[edit] Typical projectile speeds

Projectile	Speed (m/s)	(fps)	(mph)
object falling 1 m	4.5 m/s	15 fps	10 mph
object falling 10 m	14 m/s	46 fps	31 mph
thrown club (weapon) (expert thrower)	40 m/s	130 fps	90 mph
object falling 100 m	45 m/s	150 fps	100 mph
refined (= flexible) atlatl dart (expert thrower)	45 m/s	150 fps	100 mph
80-lb-draw pistol crossbow bolt	58 m/s	190 fps	130 mph
paintball fired from marker	91 m/s	300 fps	204 mph
175-lb-draw crossbow bolt	97 m/s	320 fps	217 mph
air gun pellet 6 mm BB	100 m/s	328 fps	224 mph
rifle bullet 4,5 mm	150 m/s	492 fps	336 mph
air gun pellet (conventional maximum)	244 m/s	800 fps	545 mph
9x19 mm (pistol)	340 m/s	1116 fps	761 mph
12,7x99 mm (heavy machine gun)	800 m/s	2625 fps	1790 mph
5,56x45 mm (G36 assault rifle)	920 m/s	3018 fps	2058 mph
125x1400 mm (tank)	1700 m/s	5577 fps	3803 mph
ICBM reentry vehicle	up to 4 km/s
projectile of light gas gun	up to 7 km/s
Exoatmospheric Kill Vehicle	closing speed roughly 10 km/s
projectile (e.g. space debris) and target both in LEO	closing speed 0 - 16 km/s

[edit] 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.