By Marshall Brain
A cruise missile is basically a small airplane with no pilot. Cruise missiles have a wingspan of 8.5 feet, use turbofan engines, and can 500 to 1,000 miles, depending on the configuration.
A cruise missile's purpose is to deliver a 1,000-pound high-explosive bomb to a very precise target location. The missile itself is destroyed when the bomb explodes. Most of the cruise missiles we hear about in the news are Tomahawk cruise missiles that launched from destroyers.
Cruise missiles are 20 feet long and 21 inches (0.52 meters) in diameter. When launched, they include a 550-pound solid rocket booster, and weigh about 1.5 tons. The booster falls away once its fuel is burned up. At that point, the wings, tail fins and air inlet unfold, and the turbofan engine takes over. The turbofan engine produces about 600 pounds of thrust by burning approximately 150 gallons of RJ4 fuel from the time of launch. These missiles reach a cruising speed of nearly 550 mph.
The value of cruise missiles is their incredible accuracy. It's commonly stated that they "can fly 1,000 miles and hit a target the size of a single-car garage." Cruise missiles are also fly very low to the ground , keeping them out of range of most radar detection systems.
There are four systems that guide a cruise missile to its target: the Inertial Guidance System (IGS); Terrain Contour Matching (Tercom); a Global Positioning System (GPS), and Digital Scene Matching Area Correlation (DSMAC). The IGS roughly keeps track of where the missile is located based on detected acceleration. Tercom employs an on-board 3-D terrain database, which "sees" the terrain it is flying over using radar and matches this to the 3-D map stored in memory. Tercom is responsible for a cruise missile's ability to "hug the ground" during flight. GPS uses the military's network of satellites, and an onboard GPS receiver, to detect its position very accurately. Once a missile is near its target, it switches to a "terminal guidance system" to choose the point of impact, which may be pre-programmed by the GPS or Tercom system. The DSMAC system employs a camera along with an image correlator to locate a target, and can be especially useful if a target is moving. A cruise missile may also carry thermal imaging or illumination sensors similar to those used in smart bombs.
