I have received a number of questions from those who find the distinction between a guided-unguided rocket and missile confusing.
The three key elements that distinguish one type of
weapon from another are the warhead, the
means of propulsion, and the presence of a guidance system. In this
explanation, let's follow the conventions
used by the US military in its missile
and munitions designation systems.
Let's first start
by defining a rocket, Rockets are
typically classified by the maximum diameter of the body tube. A particularly
common type in the US military is the 2.75-inch (70-mm) rocket, also known as
the Hydra 70. The US military also designates rockets with the term RLU for
Live Rocket Unit, or RBU for Rocket and Launcher Unit. These rockets are often
carried on attack helicopters like the AH-64 Apache and AH-1 Cobra. Larger
types of rockets have also been frequently used on both helicopters and
fixed-wing aircraft. Among these are the 5-inch (127-mm) Zuni rocket developed
by the US while Russian attack helicopters like the Mi-24 often carry 57-mm,
80-mm, 160-mm, 210-mm, or 240-mm rockets. The SU-17 attack fighter has even
been known to carry rockets up to 370-mm (14.5-in) in diameter.
Rockets are
usually laden with less amount of explosive when compared to a missile which is
heavier and packs more punch. Rockets are rarely used for Air to Air combat since the target will have to visually be a the
same spot which is unlikely to happen in air to air combat. Hence Rockets are
generally used only for Air to ground
combat.
A rocket would be
a powered/ ballistic trajectory only. Guided rockets can be semi-active homing
types that is they can do minor course corrections mid flight to reach a specific
target once the target is designated. Unguided rockets follow line of sight and
hence the pilot will have to aim specifically at the target while firing the
rocket.
If we take this
unguided rocket and now add a guidance
system, the result is a missile.
A missile contains all three of the elements which I have discussed a warhead, a
propulsion system, and some form of guidance. A guidance system mates a sensor
or seeker that detects a target to a computer autopilot that commands a control
system to steer towards that target. The most common types of seekers or
sensors used today include infrared, radar, lasers, inertial, and GPS. It is
the use of these guidance systems that turns a dumb weapon into a smart weapon.
Missiles are
usually classified according to their mission, such as air-to-air missiles designed to engage enemy aircraft or air-to-ground missiles designed to
attack targets on the surface. The US, for example, designates missiles with
names like AIM for Air Intercept
Missile and AGM for Air Surface-attack
Missile. This mission largely dictates the design of a missile, from its seeker
to its warhead to its propulsion to its control system. Air-to-air missiles,
like the American AIM-9 Sidewinder
or Russian R-77 Adder, are usually
small and light since they carry small warheads to attack lightly armored
targets.
A strategic weapon is one designed for mass destruction like a nuclear missile. The weapon is a guided
missile with a propulsion system during launch, this booster burns out during flight.
The purpose of the booster, usually a solid or liquid rocket, is to push the
warhead out of the atmosphere and into space. The warhead then follows an
unguided suborbital trajectory. Under the influence of gravity, the warhead
falls back into the atmosphere and takes a ballistic re-entry path to reach its
target. Ballistic missile is based on a design in use since the German V-2 rocket which the Nazis used during World War-II to terrorize and kill the
British.
As the US got more
weapons, they began making a difference between strategic
and tactical based on the delivery
system rather than the target (pre-H-bomb ). Long and medium-range
bombers were considered strategic(wherever
they were stationed), while smaller aircraft were considered tactical. Now since this had nothing to do
with the targets they would be hitting, it didn't make much sense and the
terminology was changed in the 1950s.
Various countries
more or less agreed on 5 categories of nuclear weapons:
1) Intercontinental weapons: Weapons that
would be launch from one continent and hit a target
in another. The Soviet
called these 'transoceanic' weapons.
2) Pre-strategic
Weapons: Intercontinental weapons not used against intercontinental
targets.
3) Theatre weapons:
Weapons that would hit targets deep within enemy territory but short of intercontinental ones.
4) Tactical weapons:
Weapons used against tactical non-urban-industrial targets.
5) Battlefield weapons:
Weapons used against military units on the front lines.
So these days, a strategic weapon is
considered to be either an ICBM,
SLBM, or long- range bomber. While
all the others are non-strategic.
