Stinger missile is something that appears in the news every
time there is an armed conflict involving United States
forces. It also appears after certain airline accidents -- the
one involving TWA flight 800 is a recent example. The reason
we hear so much about the Stinger in these contexts is because
the Stinger missile is an extremely effective weapon for
shooting down aircraft. The missile uses an infrared seeker to
lock on to the heat in the engine's exhaust, and will hit
nearly anything flying below 11,000 feet.
In this edition of HowStuffWorks,
you will have a chance to learn about the Stinger missile.
What sorts of aircraft can it hit? Why is it so effective? You
will also learn about the role of the Stinger missile in
The Stinger missile, officially
known as the FIM-92A, is designed to give ground troops
a way to deal with low-flying airplanes
From the perspective of soldiers on the ground, low-flying
enemy aircraft are normally a problem because they are either
bombing or strafing, doing surveillance work or inserting,
extracting and resupplying enemy troops. Shooting down these
aircraft is the easiest way to eliminate the threat.
Photo courtesy U.S. Department of
Marines launch a
Stinger anti-aircraft missile at a target aircraft
during a live fire
There are four things that make the Stinger such an
effective weapon for ground troops to use:
seeker is able to lock on to the heat that the aircraft's
engine is producing. It is called a "passive" seeker because,
unlike a radar-guided
missile, it does not emit radio waves
in order to "see" its target.
- It is a lightweight, portable weapon. The missile and
its launcher weigh about 35 pounds (15 kg). The launcher is
reusable. Each missile is a sealed unit that weighs only 22
pounds (10 kg).
- It is a shoulder-launched weapon, and one person can
launch a Stinger missile (although you normally see a
two-man team operating the missile).
- It uses a passive infrared seeker.
- It is a fire-and-forget weapon.
Launching the Missile
Here are the basic
parts of a Stinger missile:
And here are the basic parts of the launching system:
To fire the weapon, the soldier aims the missile at the
target. When the seeker locks on, it makes a
distinctive noise. The soldier pulls the trigger, and
two things happen:
The missile then flies to the target
automatically and explodes.
- A small launch rocket shoots the missile out of
the launch tube and well clear of the soldier who is firing
- The launch engine falls away and the main
solid rocket engine lights. This rocket
propels the Stinger to approximately 1,500 mph (2,400 kph,
The Stinger missile can hit targets flying as high as
11,500 feet (3,500 m), and has a range of about 5 miles (8
km). This means, in a general way, that if an airplane is less
than 2 miles high and it is visible as a shape (rather than a
dot), then it is likely that the Stinger can hit it. Stinger
missiles are extremely accurate.
Stinger missiles (as well as Sidewinder
missiles) use passive infrared seekers. In other
words, the missiles look for the infrared
light produced by the hot engine components on the
airplane and track the airplane by following that light.
If you have read about motion
detectors, you know that motion-sensing lights also use
passive infrared sensors. The sensors in a motion-sensing
light are tuned to the temperature of a human being. They look
out at the world, and when they see a sudden change in the
amount of infrared light they are sensing, they assume it's
because a person walked into the area, and they turn on the
A motion-sensing light needs only one sensor. A Stinger
missile needs a whole array of them, because its job is to
track the target while it is flying. The nose of a Stinger
missile has, essentially, an infrared digital
camera in it. This camera might have an array of anything
from 2x2 (in older designs) to 128x128 (in the newest Sidewinder
design) infrared sensors that receive an infrared image of
the scene. When the soldier gets ready to launch the missile,
the missile must have the target visible in roughly the center
of this sensor.
While the missile is flying, the image of the airplane that
it is trying to hit may become off-center on the image sensor.
When it does, that tells the missile that it is off-course,
and the guidance system in the missile has to decide how to
get back on course. This is where proportional
navigation comes in. The missile looks at the angle of
off-centeredness and changes its angle of flight
proportionally. In other words, it uses a multiplier. If the
multiplier is 2, then if the guidance system thinks it is 10
degrees off course, it will change its flight direction by 20
degrees. Then, a tenth of a second later it will look at the
angle again, and change again. By over-correcting this way, it
lets the missile anticipate the path of the moving plane in
the same way that you anticipate the path of a moving object.
If you are a quarterback trying to throw a ball to a receiver
running across the field, you would not throw the ball toward
where the receiver is -- you would throw it toward where he
will be when the ball arrives.
Obviously, the guidance system is more involved than this.
The image sensor is riding on a rotating, gyrating missile at
Mach 2, and it is trying to hit a small target that may be
flying at Mach 1. It is not a simple problem. But this is the
The reason for using an infrared sensor rather than a
normal visual sensor like you have in a video
camera is because it simplifies the image processing task.
In general, there will only be one hot object in the missile's
field of view, so with its infrared sensor it can see that hot
object very easily -- it stands out like a sore thumb. With a
visual image, the image recognition problem is much harder to
Here are the stats on the Stinger
- Length - 5 feet (1.5 meters)
- Diameter - 2.75 inches (7 cm)
- Weight - 22 pounds (10 kg)
- Weight with launcher - 34.5 pounds (15.2 kg)
- Explosives - 2.2 pounds, impact fuze (explodes on
contact with target)
- Speed - 1,500 mph (2,400 kph, Mach 2)
- Altitude Range - Approximately 11,000 feet (3 km)
- Distance Range - Approximately 5 miles (8 km)
The Afghanistan Connection
In 1986, when
Afghan rebels were fighting the Soviet Union for control of
Afghanistan, the United States gave the rebels approximately
900 Stinger missiles to use in the war. The Afghans were able
to shoot down hundreds of Soviet helicopters using the Stinger
missiles they received.
The rebels are thought to still have in their possession a
number of the missiles. When you hear news reports that
indicate that American bombers are flying at high altitudes
over Afghanistan, fear of these left-over Stinger missiles is
one reason why. It is also thought that Iran, Iraq, and
Palestinian groups have Stinger missiles obtained through
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