Kinetic energy weapon

Kinetic weapons are the oldest and most common ranged weapons used in human history, with the projectiles varying from blunt projectiles such as rocks and round shots, pointed missiles such as arrows, bolts, darts, and javelins, to modern tapered high-velocity impactors such as bullets, flechettes, and penetrators.

Typical kinetic weapons accelerate their projectiles mechanically (by muscle power, mechanical advantage devices, elastic energy or pneumatics) or chemically (by propellant combustion, as with firearms), but newer technologies are enabling the development of potential weapons using electromagnetically launched projectiles, such as railguns, coilguns and mass drivers.

[1] For a kinetic energy weapon in the aerospace field, both objects are moving and it is the relative velocity that is important.

Because the interceptor may not be approaching head-on, a lower bound on the relative velocity on the order of 16,000 miles per hour (26,000 km/h) can be assumed,[2] or converting to SI units, approximately 7,150 m/s.

[2] It may seem like this makes a warhead superfluous, but a hit-to-kill system has to actually hit the target, which may be on the order of half a meter wide, while a conventional warhead releases numerous small fragments that increase the possibility of impact over a much larger area, albeit with a much smaller impact mass.

This has led to alternative concepts that attempt to spread out the potential impact zone without explosives.

Since in order to reach an object in orbit it is necessary to attain an extremely high velocity, their released kinetic energy alone is enough to destroy their target; explosives are not necessary.

For comparison, 50 MJ is equivalent to the kinetic energy of a school bus weighing 5 metric tons, traveling at 509 km/h (316 mph; 141 m/s).

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.

When targeting objects in spaceflight, the final part of the kinetic vehicle's travel occurs in thin atmosphere or the near-vacuum of space.

[8] This kind of design is found in many anti-missile and anti-satellite weapons, including the RIM-161 Standard Missile 3[9] and THAAD.

Every part of the weapon, including the airframe, electronics and even the unburned maneuvering fuel contributes to the destruction of the target.

The main disadvantage of the kinetic energy weapons is that they require extremely high accuracy in the guidance system, on the order of 0.5 metres (2 ft).

The Homing Overlay Experiment used a metal fan that was rolled up during launch and expanded during flight. The metal has five times as much destructive power as an explosive warhead of the same weight.
Sample from a kinetic energy weapon test. A piece of polycarbonate plastic weighing 7 grams ( 1 ⁄ 4 oz) was fired at an aluminium block at 7 km/s (23,000 ft/s), giving it muzzle energy of 171,500 J (126,500 ft⋅lbf); a typical bullet has muzzle energy of a few thousand joules, with the enormous .950 JDJ reaching 20,000 J (15,000 ft⋅lbf).