A
projectile is any object propelled through space
by the exertion of a
force which ceases after
launch. Although a thrown
baseball
could be considered a projectile, the word more often refers to a
weapon. For details of the mathematics
surrounding projectile
trajectory, see
equations of motion.
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.
shell,
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 and
round
shot,pointed ones such as
arrows, and
somewhat pointed ones such as
bullets. Among
projectiles which do not contain explosives are those launched from
railguns,
coilguns,
and
mass drivers, as well as
kinetic energy penetrators. All of
these weapons work by attaining a high
muzzle velocity (
hypervelocity), and
collide with their objective, converting their
kinetic energy into destructive shock
waves and heat.
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.
[22235] 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 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.
Typical projectile speeds
| Projectile |
Speed (m/s),(km/h) |
(ft/s) |
(mph) |
Kinetic energy density =
Speed^2 / 2 |
| object falling 1 m |
4.43 m/s, 15.948 km/h |
14.5 ft/s |
9.9 mph |
9.8 J/kg |
| object falling 10 m |
14 m/s, 50.4 km/h |
46 ft/s |
31 mph |
98 J/kg |
| thrown club (expert thrower) |
40 m/s, 144 km/h |
130 ft/s |
90 mph |
800 J/kg |
| object falling 100 m |
45 m/s, 162 km/h |
150 ft/s |
100 mph |
980 J/kg |
| refined (= flexible) atlatl dart (expert
thrower) |
45 m/s, 162 km/h |
150 ft/s |
100 mph |
1000 J/kg |
| 80-lb-draw pistol crossbow bolt |
58 m/s, 208.8 km/h |
190 ft/s |
130 mph |
1.7 kJ/kg |
| paintball fired from marker |
91 m/s, 327.6 km/h |
300 ft/s |
204 mph |
4.1 kJ/kg |
| 175-lb-draw crossbow bolt |
97 m/s, 349.2 km/h |
320 ft/s |
217 mph |
4.7 kJ/kg |
| air gun pellet 6 mm BB |
100 m/s, 360 km/h |
328 ft/s |
224 mph |
5 kJ/kg |
| rifle bullet 4.5 mm |
150 m/s, 540 km/h |
492 ft/s |
336 mph |
11 kJ/kg |
| air gun pellet (conventional
maximum) |
244 m/s, 878.4 km/h |
800 ft/s |
545 mph |
29.8 kJ/kg |
| 9x19 mm (bullet of a pistol) |
340 m/s, 1224 km/h |
1116 ft/s |
761 mph |
58 kJ/kg |
| 12.7x99 mm (bullet of a heavy machine gun) |
800 m/s, 2880 km/h |
2625 ft/s |
1790 mph |
320 kJ/kg |
| 5.56x45 mm (standard bullet
used in many assault rifles) |
920 m/s, 3312 km/h |
3018 ft/s |
2058 mph |
470 kJ/kg |
| 125x1400 mm (shell of a tank) |
1700 m/s, 6120 km/h |
5577 ft/s |
3803 mph |
1.4 MJ/kg |
| 2kg Tungsten Slug (from Experimental Railgun) |
3000 m/s, 10800 km/h |
9843 ft/s |
6711 mph |
4.5 MJ/kg |
| ICBM reentry
vehicle |
up to 4 km/s |
up to 13000 ft/s |
up to 9000 mph |
up to 8 MJ/kg |
| projectile of a light gas gun |
up to 7 km/s |
up to 23000 ft/s |
up to 16000 mph |
up to 24 MJ/kg |
| satellite in low earth
orbit |
8 km/s |
26000 ft/s |
19000 mph |
32 MJ/kg |
| Exoatmospheric Kill
Vehicle |
closing speed roughly 10 km/s |
~33000 ft/s |
~22000 mph |
~ 50 MJ/kg |
| projectile (e.g. space debris) and
target both in low earth orbit |
closing speed 0 - 16 km/s |
~53000 ft/s |
~36000 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
fragments.
Projectile is also the name of an annual anarchist film festival
based in Newcastle UK *
[22236]
See also
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