How Stinger missiles work
By Marshall Brain
http://www.JewishWorldReview.com | (MCT) Last month police recovered what is reported to be a missile launcher from the front yard of a New Jersey home. Even more troubling is the fact that the home stands in the flight path for the Newark airport. If the device actually is a shoulder-launched anti-aircraft weapon, then chances are that it will be very much like the U.S. Stinger missile. By understanding how a Stinger missile works, you can see why people are so nervous about these weapons being in the hands of terrorists.
The Stinger missile is designed to give ground troops a way to deal with low-flying airplanes and helicopters. On the battlefield, a Stinger missile is a very handy tool for eliminating enemy aircraft that may be bombing, strafing or watching soldiers on the ground. From a soldier's standpoint there are many advantages to the Stinger. First, it is a lightweight, portable weapon. The missile and its launcher weigh about 35 pounds and 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. The Stinger is also a fire-and-forget weapon. Once launched, the Stinger missile finds its target without the soldier needing to watch or guide it.
A Stinger missile is essentially a little 20 pound flying robot. It has a small microcomputer brain and a simple eye that is sensitive to the bright infrared light given off by a hot engine. The missiles also identify the UV "shadow" of the target and use that identification to distinguish the target from other heat-producing objects.
The nose of a Stinger missile has, essentially, an infrared digital camera in it that receives 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.
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. First, a small launch rocket shoots the missile out of the launch tube and well clear of the soldier who is firing it. Then the launch engine falls away and the main solid rocket engine lights. This rocket propels the Stinger to approximately 1,500 mph (Mach 2). The missile flies to the target automatically and explodes.
While the missile is flying, the image of the airplane that it is trying to hit may become off-center on the infrared 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. The missile looks at the angle of off-centeredness and changes its angle of flight proportionally. By doing this dozens of times per second, the missile stays right on target.
A Stinger missile has a range of about five miles, and it can hit an airplane that is two miles up. The missile's bomb weighs about six pounds, and it explodes on contact with the airplane. The range of the Stinger and the size of the bomb makes a jumbo jet cruising along at take-off or landing speeds a sitting duck.
Several other countries make shoulder-launched missiles like the Stinger, so these devices are not exactly rare. Therefore, you might be wondering if there is any way to protect planes from this type of weapon. One standard technique used to confuse heat-seeking missiles is for a plane to drop flares. With luck the missile locks onto the heat from the flares rather than the engines and completely misses the plane. The president's 747 (Air Force One), along with many military aircraft, have these flares. They also have radio equipment to confuse other types of missiles as well. The problem is that these systems are expensive, and there are about 7,000 or so commercial airliners flying in the United States. It would cost billions of dollars to equip the whole fleet, so it may be years before we see any of these systems installed.
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© 2007, How Stuff Works Inc. Distributed by McClatchy-Tribune Information Services.