Direct fire

Direct fire is a military term for battlefield weapons fired with a direct line of sight on their target. Depending on the weapon and its projectile speed -- not a concern with evolving laser weapons -- it may be necessary to "lead" a moving target such as an airplane, so that the projectile arrives in the same place the target will be at its current range of motion.

While there may be a direct line of sight, there still may need to be corrections for wind, gravitational effects on the projectile, and the accuracy of the weapon. Basic individual weapons such as rifles and pistols are the most obvious direct fire, but so are unguided rocket launchers such as the AT-4, the gun of a main battle tank such as the M1 Abrams or Chieftain,

This allows them to fire over obstacles, and also to engage targets at greater range than can direct fire weapons. The most common indirect fire weapons are mortars, howitzers, and multiple rocket launchers. Some types of weapons, usually used for indirect fire, can be used in direct fire. sights", typically in final defense of the howitzer position.

Indirect fire trajectories

The basic trajectory of an direct fire weapon is a parabola, but, for short distances, it may be approximated as a straight line.

• Energy imparted by the gun propellant or rocket motor; there may be gravity-induced drop over long distances
• Barrel angle (i.e., elevation of the tube)

Of course, weather may affect the flight; wind usually needs to be considered. Firing through rain can be very unpredictable.