Tomahawk cruise missiles frequently appear in the news because they are the U.S. weapon of choice for a variety of quick-strike operations. In this issue of Stuff.dewsoftoverseas.com we will look at cruise missiles so that you can understand what they are and how they work. Then you can explore a wide variety of links for additional information!

The Basics
A cruise missile is basically a small, pilot-less airplane. Cruise missiles have an 8.5-foot (2.61 meter) wingspan, are powered by turbofan engines and can fly 500 to 1,000 miles depending on the configuration. A cruise missile's job in life is to deliver a 1,000 pound (450 kg) high-explosive bomb to a precise location - the target. The missile is destroyed when the bomb explodes. Since cruise missiles cost between $500,000 and $1,000,000 each, it's a fairly expensive way to deliver a 1,000 pound package!



Cruise missiles come in a number of variations (see the links section for details) and can be launched from subs, destroyers or aircraft. When you hear about hundreds of cruise missiles being fired at targets like Iraq, they are almost always Tomahawk cruise missiles launched from destroyers.



Dimensions
Cruise missiles are 20 feet (6.25 meters) long and 21 inches (0.52 meters) in diameter. At launch they include a 550 pound (250 kg)
solid rocket booster and weigh 3,200 pounds (1450 kg). The booster falls away once it has burned its fuel. The wings, tail fins and air inlet unfold, and the turbofan engine takes over. This engine weighs just 145 pounds (65 kg) and produces 600 pounds of thrust burning RJ4 fuel. The fuel load is 800 to 1,000 pounds (450 kg) of fuel at launch, or approximately 150 gallons (600 liters). A cruise missile has a cruising speed of 550 mph (880 km/h).

Guidance
The hallmark of a cruise missile is its incredible accuracy. A common analogy used when talking about cruise missiles is, "the missile can fly 1,000 miles and hit a target the size of a single-car garage!" Cruise missles are also very effective at evading detection by the enemy because they fly very low to the ground (out of the view of most radar systems). Four different systems help guide a cruise missile accurately to its target:

  • IGS - Inertial Guidance System
  • Tercom - TErrain COntour Matching
  • GPS - Global Positioning System
  • DSMAC - Digital Scene Matching Area Correlation
The IGS is a standard acceleration-based system that can roughly keep track of where the missile is based on the accelerations it detects in the missile's motion (Click here for a nice intro article). Tercom uses an on-board 3-D database of the terrain the missile will be flying over. The Tercom system "sees" the terrain it is flying over using its radar system and matches this to the 3-D map stored in memory. The Tercom system is responsible for a cruise missile's ability to "hug the ground" during flight. The GPS system uses the military's network of GPS satellites and an onboard GPS receiver to detect its position with very high accuracy.

Once it is close to the target, the missile switches to a "terminal guidance system" to choose the point of impact. The point of impact could be pre-programmed by the GPS or Tercom system. The DSMAC system uses a camera and an image correlator to find the target, and is especially useful if the target is moving. A cruise missile can also be equipped with thermal imaging or illumination sensors (as used in smart bombs).

Additional HSW articles
If you are a fan of Stuff.dewsoftoverseas.com you may have noticed that cruise missiles use a number of different technologies that are discussed in detail in other HSW articles. Here is a list of those articles:

Links
General

Launch systems Other