Guided missiles work by tracking the location of the moving target in space by certain methods (eg . using a radar or following its heat signature), chasing it down and then finally hitting it with accuracy. Guided systems in missiles can be of various types, which serve different operational purposes.
Missiles have been around for quite some time now. In fact, humans have been using missiles – in various forms – for centuries. However, just as it happens with everything else, the technology of missiles has also improved dramatically over the past century. On today’s high-tech battlefields, we have guided missiles packed with explosive warheads that have become the devastating weapon of choice to destroy targets swiftly and with amazing accuracy.
According to the ‘profile’ of the target, guidance systems can be classified into two types: Go-Onto-Location-in-Space (GOLIS) and Go-Onto-Target (GOT). While GOLIS systems are usually limited to stationary or near-stationary targets, GOT systems prove to be highly effective in taking down both stationary and moving targets.
Now, let’s take a look at the main systems that are currently being used to implement various guidance control rules in missiles.
Commonly referred to as the LOS system, this type of control system consists of three components: a reference point (usually a radar station), a missile, and a target. Its mode of operation is also rather straightforward: the radar station tracks the target continuously (regardless of whether it’s moving or not) and emits a beam leading up to the target. If the missile has enough fuel to reach the target, maintains a decent relative velocity and stays on the beam, then it will make the hit.
Limitations
The most glaring limitation of LOS systems is that they are almost rendered useless in situations where the target is using evasive maneuvers. Since most airborne targets involved in militaristic operations (like fighter jets) are rather good at climbing and diving swiftly, dodging LOS missiles is fairly easy for them. Also, you wouldn’t want to use an LOS missile to hit a target that’s approaching the reference point directly, since it’s out of their operational capacity to make increasingly tighter turns to stay on target.
Pursuit system
As the name signifies, the fired missile in this system automatically stays on the target and continues pursuit it until it makes the hit. As opposed to the LOS system, this guidance system involves only two players: the missile and the target. This system also has two variants, namely Altitude Pursuit (AP) and Velocity Pursuit (VP).
In AP, the axis of the missile is kept pointing towards the target, whereas in VP, the velocity vector of the missile is kept pointing at the target. These two axes, i.e. the axis of the missile and its angle of attack, are usually not the same, as the missile sometimes skids as it flies through the air.
Installed at the head of the missile is some type of tracking system, like a radar system (an active homing technique) that receives emissions from the target, or an infrared optical sensor that tracks and pursues the heat signature of the target (the IR sensor in the missile tracks the heat emitted by jet exhausts). The latter system is called infrared homing (a passive homing technique); you have almost certainly seen the implementation of such systems in heat-seeking missiles in movies. Here’s one missile chase scene from Behind Enemy Lines
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