Fighter Combat - Tactics and Maneuvering

34 FIGHTER WEAPONS
Missile Guidance
The guidance system provides inputs to the missile control system, which
in turn maneuvers the missile to intercept the target. Guidance for AAMs
and SAMs can be classified as one of the following: preset, command,
beam-rider, and homing.
Preset guidance means that a prelaunch determination is made of the
missile-target intercept point in space. Prior to missile launch the guidance
system is provided with this information and the trajectory to be
followed (by dead reckoning, inertial, or some other form of navigation) to
the missile's destination. Since this information cannot be changed after
the missile is fired, any inherent system inaccuracy or postlaunch target
maneuver may result in a wide miss. Preset guidance is therefore closely
related to the unguided rocket, and it is applicable to the anti-air mission
only in conjunction with very large warheads (nuclear) or as an initial
guidance mode in combination with more accurate terminal guidance
techniques.
Command guidance may be likened to classic remote control. During
missile flight the positions of both the target and the missile are monitored
at the launching platform, and commands are sent to the missile to fly a
course that will result in target interception. Tracking of target and missile
is usually accomplished by radar, through electro-optics (television), or by
sight. Of these three methods, only radar generally provides target/missile
range information sufficiently accurate to allow computing of a leadintercept
trajectory for the missile, but since two tracking radars are
usually required, this technique largely has been limited to SAM systems.
Without range data the missile is ordinarily guided along the LOS between
the target and the launcher. This technique, known as "command-to-
LOS," can be accomplished with no range information at all and is applicable
to visual and electro-optical systems as well as to radar and combination
systems.
The guidance instructions to the missile are generally transmitted by
radio data link, which is susceptible to jamming, as are most radar trackers.
Trailing wires (wires connecting the missile and the launch platform)
have been used for transmitting guidance commands with much success
in several short-range air-to-surface and surface-to-surface applications.
Such a system is highly resistant to jamming, and was employed by the
first AAM. This was a German X-4, designed and tested late in World War
II for use by the Me 262 and Fw 190. The X-4 was a command-to-LOS
trailing-wire system that was controlled manually by the launching pilot
along the visual LOS to the target aircraft. Apparently it was never used
operationally.
Beam-rider guidance is somewhat similar to command-to-LOS guidance,
except that the missile guidance system is designed to seek and
follow the center of the guidance beam automatically, without specific
correction instructions from the launching platform. The guidance beam
may be provided by a target-tracking radar, by electro-optics, or by a visual
system. Like radar-enhanced command guidance systems, radar beamrider
systems are not limited to daylight, good-weather conditions, but