Fighter Combat - Tactics and Maneuvering

FIGHTER WEAPONS 35
they are more susceptible to electronic countermeasures than are electrooptical
and visual trackers.
One problem with beam-rider systems, as with command-to-LOS, is
that the missile must have high maneuverability in order to intercept an
evasive target. As they approach the target, beam-rider missiles often must
tighten their turns continually to keep up. At high speeds tight turns may
exceed the missile's capabilities. Using two radars, one for target tracking
and a second for missile tracking and guidance, can reduce this problem
somewhat by providing a more efficient lead trajectory, but such systems
are more complex and their use is generally limited to SAMs. Beam-rider
guidance, however, is usually more accurate and faster-reacting than command
guidance systems, and it can be quite effective against even evasive
aircraft targets.
The most effective type of guidance against evasive targets is homing.
Within this broad category are three subtypes: passive, semi-active, and
active. The simplest of these, passive homing, relies on emissions given off
by the target itself (e.g., sound, radio, radar, heat, light) for its guidance
information. Semi-active homing systems guide on energy reflecting off
the target. This energy, usually radar or laser, is provided by a source
external to the missile, often the launching platform. For active homing
guidance the missile itself illuminates and tracks the target.
Before examining these guidance systems in more detail it would be
helpful to investigate variations in missile trajectories. Figure 1-7 illustrates
some rather simplified missile trajectories where the speed of the
missiles is constant (about 1.5 times the target speed) and the target flies a
TARGET
TRACK
PURE
PURSUIT
(PP)
MISSILE
TRACKS
Figure 1-7. Pursuit Trajectories
LEAD
COLLISION
'2 (LC)
INTERCEPT POINTS
LEAD
PURSUIT
(LP)
LP