Projectile
A projectile is any object sent 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.
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.
Blunt or sharp
Although blowguns use small darts, most types of guns and firearms hurl bullets, pellets, or shot made of a metal, usually lead, that are designed to deform and fragment inside a target, causing significant damage. Items like arrows, hand darts, and spears are generally tipped with sharp metallic or lithic artifacts called projectile points that allow them to more easily penetrate a target, although some types of arrows used for hunting are designed to stun or kill through shock rather than to penetrate.
Projectiles designed to be non-lethal, for example for use against riots, include rubber bullets and flexible baton rounds.
Kinetic projectiles
Some projectiles do not contain an explosive charge (as opposed to projectiles with 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, 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).
See also Hypervelocity terminal ballistics, Exoatmospheric Kill Vehicle (EKV).
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]
A kinetic bombardment may involve a projectile dropped from Earth orbit. For a fictional kinetic weapon, see Relativistic kill vehicle.
Typical projectile speeds
| Projectile | Speed |
|---|---|
| heavy object falling 1 m | 4.5 m/s |
| heavy object falling 10 m | 14 m/s |
| heavy object falling 100 m | without air resistance 45 m/s |
| air gun bullet 6 mm BB | 100 m/s |
| rifle bullet 4,5 mm | 150 m/s |
| speed of impact of dropped concrete-filled bomb | 200 m/s |
| 9x19 mm (pistol) | 340 m/s |
| 12,7x99 mm (heavy machine gun) | 800 m/s |
| 5,56x45 mm (G36 machine gun) | 920 m/s |
| 125x1400 mm (tank) | 1700 m/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 |
See also Orders of magnitude (speed), Muzzle velocity.
Miscellaneous
Ballistics analyses 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.