How a cruise missile works
By Marshall Brain
http://www.JewishWorldReview.com | (MCT) We hear about cruise missiles on the news all the time. At the beginning of a war, the United States has been known to launch a hundred or more Tomahawk cruise missiles. Cruise missiles can also be used one or two at a time. There is often speculation about the possibility of using a cruise missile to hit specific targets in enemy countries.
Which leads to the obvious question: what is a cruise missile? And why are they so popular?
If you want to put it as succinctly as possible, a cruise missile is a small, robotic jet airplane that can automatically deliver a bomb to its target. No human intervention is involved, even though the missile may fly more than 1,000 miles to the target. The Tomahawk cruise missile makes a great example, so let's look at the details of this flying robot.
A Tomahawk is basically a tube that is 20 feet long and 21 inches in diameter. It weighs 3,200 pounds at launch. For comparison, a 2006 Honda Civic is 14 feet long and weighs about 2,700 pounds. Unlike a Honda Civic, a Cruise Missile has two little wings that pop out once it launches, and it flies as fast as a jet airplane.
The launch is pretty spectacular. A cruise missile can launch from an airplane, the deck of a ship or the back of a truck. But the missile needs a big kick to get it moving. A 550-pound solid rocket engine gives it that kick. Once the rocket burns out, it falls away, the wings pop out and a little turbo fan engine in the back of the missile provides the power for flight.
Turbo fan engines are common - whenever you get on a commercial jet, it is a turbo fan engine that moves you through the sky. The thing that is unique about the turbo fan on a cruise missile is its size. It only weighs 145 pounds, but it can keep the missile flying at 550 mph.
There is a big fuel tank inside the cruise missile to hold the jet fuel for this engine. The tank can hold about 150 gallons. That gives the missile a range of more than 1,000 miles.
At the front of the missile is its robot brain. The brain can do four different things. First it has the ability to track its position using GPS signals, just like a car with a navigation system. Second, it has something called an IGS, or inertial guidance system. An IGS uses accelerometers and can track where the missile is whenever it accelerates or turns. Next is Tercom, or Terrain Contour Matching. This is a very detailed map of the hills and valleys along the missile's route. Tercom lets the missile hug the ground and stay below the radar. And finally there is DSMAC, a computerized eye. The missile can actually look for its target and match it with a picture in memory. DSMAC makes it easy for the missile to hit moving targets.
The other thing inside the cruise missile tube, of course, is the bomb. It weighs 500 to 600 pounds.
In other words, a cruise missile is a flying robot that can deliver a 600-pound bomb with pinpoint accuracy. Imagine launching one of these missiles from Washington, D.C., and having it hit a specific garage in Miami two hours later without any human help. That is the power of cruise missile technology.
The fascinating thing is that many other countries are now beginning to deploy their own cruise missiles. Russia, for example, is thought to have something called a Moskit missile. It flies at two times the speed of sound, skimming at an altitude of just a few meters above the surface of the ocean, and it carries a 750-pound bomb. If a U.S. aircraft carrier were to get hit by one of those, we might start looking at cruise missile technology in a whole new light.
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© 2007, How Stuff Works Inc. Distributed by McClatchy-Tribune Information Services.