Ballistics, study of the motion of projectiles. It consists of two main branches, interior ballistics and exterior ballistics. Interior ballistics deals with the motion of the projectile inside the bore of the gun, and is concerned with providing a theoretical basis for the methods and rates of burning the various kinds and shapes of propellants, the ultimate object being the determination of the maximum pressure set up by the gases inside the gun, and the velocity with which the projectile is ejected from the muzzle.
The theory having been developed, the practical application is the fixing of the weight of the propellant, and the size and shape of its component pieces or grains, necessary to produce any desired velocity in a particular gun without subjecting it to a pressure greater than the material can stand. The consideration of the stresses in the material itself belongs to the province of the gun construction and design. Exterior ballistics deals with the motion of the projectile outside the bore, and its principal problem is the calculation of the path of a given projectile once its muzzle velocity and the elevation at which it was fired are known. The solution of this problem enables the ballistics expert to construct range tables by means of which the gunner can lay his gun so as to hit a given target.
In investigating the problem, measurements have to be made to ascertain the nature and amount of the air's resistance to the shell; how its path is affected by the weight, shape, and steadiness in flight of the projectile, and how it is affected by the atmospheric conditions of temperature, air density, and humidity; and, finally, what amount of twist must be given to make the projectile come down nose first, and how this twist affects the flight of the projectile. These measurements are usually considered under the heading of experimental ballistics, and the term exterior ballistics is properly applied to the calculation of trajectories once the data regarding velocity, elevation, and air resistance are known.
The development of rockets, and guided, stand-off, and ballistic missiles, some of them launched from ships and aircraft, has involved the solving of many highly complex exterior ballistics and related problems. There are four main types of such weapons, surface-to-surface, surface-to-air, air-to-air and air-to-surface, and some of the long-range ballistic missiles have ranges in excess of 16,000 km.
No comments yet.