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82 Air-To-Air Missiles
AIR-TO-AIR MISSILES
Like aircraft, missiles must obey the laws of physics and have very specific flight
envelopes. When fired within the appropriate parameters, missiles have a deadly
performance advantage over aircraft. When fired in marginal situations, however,
the missile’s chances of success go down dramatically.
Kinematic Range Against Non-Maneuvering Targets
Like aircraft, a missile’s biggest problem is thrust. Missiles have a very limited
amount of space for onboard fuel. Consequently, a missile’s engine burns for a
very short time (just a few seconds in some cases) and quickly accelerates the
missile to maximum speed. The motor then burns out and the missile relies on its
rapidly decaying momentum to reach the target. As with aircraft, the missile’s turn
performance is dependent upon how many g’s it can pull. The slower the missile
is, the less g’s it can pull. The maximum range at which the missile is effective
against a non-maneuvering target is called its kinematic range. As we’ll see later,
however, “range” is a very elusive topic.
Target aspect angle has a large impact on the missile’s effective range. As shown
in the figure below, a target heading directly at the missile covers part of the
range. The shooter can fire the missile earlier since the target flies toward the
missile, shortening the missile’s time of flight. Conversely, a tail aspect greatly
reduces missile range since the target is running away from the missile. Suppose
the missile is fired at a target 10 km away. It takes the missile several seconds to
travel that distance. By the time the missile has flown 10 km, the target may have
moved another one or two kilometers further away. Missiles are substantially
faster than aircraft, but run out of fuel much faster as well.
Effects of Head and Tail Aspect Angles on Missile Kinematic Range
The left-hand illustration in the figure on the facing page shows a typical envelope
for a missile fired at a non-maneuvering target (in the center of the diagram). The
gray zone represents the ranges from which the missile may be fired based on
aspect angle. Notice that when fired head-on, the range is significantly longer than
when fired from behind. The white area around, the target defines the minimum
range requirements for the missile. Since directly hitting the target is unlikely,
most missile warheads are designed to emit some form of shrapnel in order to
damage nearby aircraft. To prevent the launching aircraft from being inadvertently
damaged by the missile explosion, the missile does not arm until it has flown a
safe distance from the shooter. Also, the missile seeker or guidance system may
require some amount of time to engage the target. The distance the missile must
fly is known as the minimum range.