Difference between revisions of "Projectile" - New World Encyclopedia

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A '''projectile''' is any object propelled through space by the exertion of a force that ceases after launch. In a general sense, even a [[Football (ball)|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 [[weapon]]s.
 
 
==Motive force==
 
[[Arrow]]s, [[dart (missile)|darts]], [[spear]]s, 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 (weapon)|bow]].
 
 
Other weapons use the compression or expansion of gases as their motive force.
 
 
[[Blowgun]]s and [[pneumatic rifle]]s use compressed gases, while most other [[gun]]s and [[firearm]]s utilize expanding gases liberated by sudden chemical reactions. [[Light gas gun]]s use a combination of these mechanisms.
 
 
[[Railgun]]s 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 missile|guided]]. Note the two meanings of "rocket": an [[ICBM]] is a missile with rocket engines.
 
 
==Non-kinetic effects==
 
Many projectiles, e.g. [[Shell (projectile)|shell]]s, 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==
 
''See also: [[KE-Munitions]]''
 
 
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 [[Rock (geology)|rock]]s and [[round shot]],
 
pointed ones such as [[arrow]]s, and somewhat pointed ones such as [[bullet]]s. Among projectiles which do not contain explosives are also [[railgun]]s, [[coilgun]]s, [[mass driver]]s, and [[kinetic energy penetrator]]s. All of these weapons work by attaining a high [[muzzle velocity]] ([[hypervelocity]]), and [[collision|collide]] with their objective, releasing [[kinetic energy]].
 
 
Some kinetic weapons for targeting objects in [[spaceflight]] are [[anti-satellite weapon]]s and [[anti-ballistic missile]]s. 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 [[trinitrotoluene|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 [[Terminal High Altitude Area Defense|THAAD]] being developed do not (see [[Missile Defense Agency]]).
 
 
A kinetic projectile can also be dropped from aircraft. In this approach, the explosives of a regular bomb may be replaced with concrete, for a precision hit that causes less [[collateral damage]].<ref>Randle, Jim. October 7, 1999. [http://www.fas.org/news/iraq/1999/10/991007-iraq.htm Concrete Bomb]. Correspondent Report, Pentagon. Retrieved January 14, 2009.</ref> A typical bomb has a mass of 900 kg and an impact speed of 800&nbsp;km/h (220 m/s). This method is also applied when training personnel in the act of dropping a bomb with explosives. It was 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 called 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 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.
 
*to make a connection with the target, either to tow it towards the launcher, as with a whaling [[harpoon]], or to draw the launcher to the target, as a [[grappling hook]] does.
 
 
== Range of a projectile ==
 
[[image:ProjectileRange.jpg|right|thumb|250 px|The path of this projectile launched from a height <var>y<sub>0</sub></var> has a range d.]]
 
 
In [[physics]], a [[projectile]] launched with specific [[initial conditions]] in a uniform [[gravity]] field will have a predictable range. This range can be calculated using the following parameters:
 
 
* <var>g</var>: the [[gravitational acceleration]]&mdash;usually taken to be 9.81 m/s<sup>2</sup> near the Earth's surface
 
* <var>θ</var>: the angle at which the projectile is launched
 
* <var>v</var>: the velocity at which the projectile is launched
 
* <var>y<sub>0</sub></var>: the initial height of the projectile
 
* <var>d</var>: the total horizontal distance travelled by the projectile
 
 
When neglecting air resistance, the range of a projectile will be
 
 
: <math> d = \frac{v \cos \theta}{g} \left( v \sin \theta + \sqrt{(v \sin \theta)^2 + 2gy_0} \right) </math>
 
 
If (<var>y<sub>0</sub></var>) is taken to be zero, meaning the object is being launched on flat ground, the range of the projectile will then simplify to
 
 
: <math> d = \frac{v^2}{g} \sin 2 \theta </math>
 
 
==Typical projectile speeds==
 
{{seealso|Orders of magnitude (speed)|Muzzle velocity}}
 
 
<!-- the 1m fall is incorrect... it'll be moving 9.8m/s after moving 4.905meters.. not 1 —>
 
<!--i changed the 1m fall  v=g*t with t=sqrt(2s/g) —>
 
{| class="wikitable"
 
! Projectile || [[Speed]] (m/s) || (ft/s) || (mph)||[[Kinetic energy]]
 
|-
 
| object [[falling]] 1&nbsp;m || 4.43 m/s || 14.5&nbsp;ft/s || 9.9&nbsp;mph||9.8 J/kg
 
|-
 
| object falling 10&nbsp;m || 14 m/s || 46&nbsp;ft/s || 31&nbsp;mph||98 J/kg
 
|-
 
| thrown [[club (weapon)]] (expert thrower) || 40 m/s || 130&nbsp;ft/s || 90&nbsp;mph || 800 J/kg
 
|-
 
| object falling 100&nbsp;m || 45 m/s || 150&nbsp;ft/s || 100&nbsp;mph||980 J/kg
 
|-
 
| refined (= flexible) [[atlatl]] dart (expert thrower) || 45 m/s || 150&nbsp;ft/s || 100&nbsp;mph || 1000 J/kg
 
|-
 
| 80-lb-draw pistol [[crossbow]] bolt || 58 m/s || 190&nbsp;ft/s || 130&nbsp;mph || 1.7 kJ/kg
 
|-
 
| [[paintball]] fired from marker || 91 m/s || 300&nbsp;ft/s || 204&nbsp;mph || 4.1 kJ/kg
 
|-
 
| 175-lb-draw [[crossbow]] bolt || 97 m/s || 320&nbsp;ft/s || 217&nbsp;mph ||  4.7 kJ/kg
 
|-
 
| [[air gun]] [[Pellet (air gun)|pellet]] 6&nbsp;mm [[BB gun|BB]] || 100 m/s || 328&nbsp;ft/s || 224&nbsp;mph || 5 kJ/kg
 
|-
 
| [[rifle]] bullet 4.5&nbsp;mm || 150 m/s || 492&nbsp;ft/s || 336&nbsp;mph||11 kJ/kg
 
|-
 
| [[air gun]] pellet (conventional maximum) || 244 m/s || 800&nbsp;ft/s || 545&nbsp;mph || 29.8 kJ/kg
 
|-
 
| 9x19&nbsp;mm (bullet of a [[pistol]]) || 340 m/s || 1116&nbsp;ft/s || 761&nbsp;mph||58 kJ/kg
 
|-
 
| 12.7x99&nbsp;mm (bullet of a heavy [[machine gun]]) || 800 m/s || 2625&nbsp;ft/s || 1790&nbsp;mph||320 kJ/kg
 
|-
 
| [[5.56 x 45 mm NATO|5.56x45 mm]] (standard bullet used in many assault rifles) || 920 m/s || 3018&nbsp;ft/s || 2058&nbsp;mph||470 kJ/kg
 
|-
 
| 125x1400&nbsp;mm (shell of a [[tank]]) || 1700 m/s || 5577&nbsp;ft/s || 3803&nbsp;mph||1.4 MJ/kg
 
|-
 
| 2kg Tungsten Slug (from Experimental [[Railgun]]) || 3000 m/s || 9843&nbsp;ft/s || 6711&nbsp;mph || 4.5 MJ/kg
 
|-
 
| [[ICBM]] [[reentry vehicle]] || up to 4&nbsp;km/s || up to 13000&nbsp;ft/s || up to 9000&nbsp;mph || up to 8 MJ/kg
 
|-
 
| projectile of a [[light gas gun]] || up to 7&nbsp;km/s || up to 23000&nbsp;ft/s || up to 16000&nbsp;mph || up to 24 MJ/kg
 
|-
 
| satellite in LEO || 8&nbsp;km/s || 26000&nbsp;ft/s || 19000&nbsp;mph || 32 MJ/kg
 
|-
 
| [[Exoatmospheric Kill Vehicle]] || closing speed roughly 10&nbsp;km/s || ~33000&nbsp;ft/s || ~22000&nbsp;mph || ~ 50 MJ/kg
 
|-
 
| projectile (e.g. [[space debris]]) and target both in [[Low Earth orbit|LEO]] || closing speed 0 - 16&nbsp;km/s || ~53000&nbsp;ft/s || ~36000&nbsp;mph || ~ 130 MJ/kg
 
|}
 
 
==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 [[Fragmentation (weaponry)|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==
 
 
* [[Arrow]]
 
* [[Ballistics]]
 
* [[Bullet]]
 
* [[Gunpowder]]
 
* [[Intercontinental ballistic missile]]
 
* [[Missile]]
 
* [[Space debris]]
 
* [[Spear]]
 
* [[Torpedo]]
 
* [[Weapon]]
 
 
== Notes ==
 
<references/>
 
 
== References ==
 
 
* Crosby, Alfred W. 2002. ''Throwing Fire: Projectile Technology Through History.'' Cambridge: Cambridge University Press. ISBN 0521791588
 
 
* Hothem, Lar. 1983. ''Arrowheads & Projectile Points.'' Paducah, KY: Collector Books. ISBN 0891452281
 
 
* McCoy, Robert. 2004. ''Modern Exterior Ballistics: The Launch and Flight Dynamics of Symmetric Projectiles.'' Atglen, PA: Schiffer Pub. ISBN 0764307207
 
 
==External links==
 
 
* [http://www.physics-lab.net/applets/projectile-motion Projectile Motion]. Physics Lab. (applet). Retrieved January 14, 2009.
 
 
[[Category:Physical sciences]]
 
[[Category:Physics]]
 
[[Category:Military technology]]
 
 
{{credits|Projectile|261895142|Range_of_a_projectile|258388651}}
 

Revision as of 22:19, 1 February 2009