Ballistics << buh LIHS tihks >> is a branch of engineering that deals with the motion and behavior of projectiles, such as bullets, rockets, bombs, and guided missiles. Research in ballistics is conducted by all branches of the United States armed forces. The United States Army carries on its primary ballistics research at the Aberdeen (Md.) Proving Ground. The U.S. Navy conducts its main ballistics research at the Naval Surface Weapons Center in Dahlgren, Va.
Ballistics is divided into three main branches: interior, exterior, and terminal ballistics. Police use a science called forensic ballistics.
Interior ballistics
deals with the motion of a projectile as it travels down the barrel of a weapon, such as a rifle, tank gun, or rocket launcher. Interior ballistics experts study the forces that affect the projectile, including its weight and speed. They also study how the projectile interacts with the barrel of the weapon.
The speed with which a projectile leaves a gun barrel or a launcher is called the initial velocity or muzzle velocity. With modern propulsion techniques, the projectile’s initial velocity may be as high as 4,000 feet (1,200 meters) per second for some rifles and 5,000 feet (1,500 meters) per second for some large guns. Ideally, the projectile should leave the gun barrel with a high initial velocity and without disturbances to the direction of its motion.
Exterior ballistics
deals with the behavior of a projectile from the time it leaves the weapon until it ends its flight. Determining the projectile’s trajectory (path) is the main problem in exterior ballistics. To determine the trajectory, an exterior ballistics expert must know the interior ballistics data, such as the initial velocity of the projectile, and the effects of gravity and air on the projectile.
The force of gravity makes the projectile fall toward the earth while in flight. The effects of air on the projectile are more difficult to predict. The amount of air resistance to a projectile depends on the projectile’s size, shape, and speed, and on the density of the air. Air resistance slows the projectile and reduces its range (distance it travels). Winds can shorten or lengthen the range. Cross winds may force the projectile to one side or another. A projectile from a rifled gun spins and behaves like a gyroscope. Air pressure on the spinning projectile causes gyroscopic precession (see Gyroscope (Precession) . This effect makes it drift slowly along a spiral path, turning in the direction of its spinning motion.
Determining trajectories involves some of the most complex problems of mathematics and physics. However, the use of supercomputers in exterior ballistics can provide solutions that are highly accurate.
Terminal ballistics
is the study of the effect a projectile has on a target and the surrounding area. Since targets can be in almost any form, the study of terminal ballistics includes many areas of structural mechanics and materials science. Recent advances in radiography (using X rays) and high-speed photography have increased knowledge in terminal ballistics.
Damage to a target can be produced by fragmentation, impact, blast, heat, fire, radiation, and chemical or bacteriological action. A projectile’s ability to damage a target depends on such conditions as the size, weight, speed, and composition of the projectile and the composition of the target.
Forensic ballistics
is a special field that helps police identify bullets fired from guns. Every gun leaves certain marks on the bullets it fires. These marks differ from those made by any other gun. As a result of this fact, ballistics experts can examine these marks and determine whether a particular bullet was fired from a particular gun.
