Ultimate umbrella

Star Wars: missile defense
Howzit work?
A tough task
When to hit that missile?


More than a blockbuster movie
Think George Lucas had a hard time coming up with a sequel -- er, prequel -- to moviedom's most lucrative series? Then think about trying to whack an inter-continental ballistic missile (ICBM) in mid-flight. The target is an object roughly a meter in diameter that's speeding through space at, say, 10,000 miles per hour -- more than 100 times freeway speed.

Your mission, should you choose to accept it, is to zap this thing with a kill vehicle -- essentially a bullet that will impact and release huge amounts of kinetic energy, deflecting or destroying the warhead outright.

The kill vehicle, which will not explode, is planned to be about 68 inches in diameter, and if you miss by a meter, you might as well miss by a mile. The warhead will continue on its merry way, with "Nuke New York" or "Obliterate Omaha" burned into its targeting mechanism.

Although an exploding defensive missile might not have to make a direct hit, the current "hit to kill" approach was chosen "it's the only way you can be absolutely sure you have destroyed the warhead and weapon," says Lt. Col. Rick Lehner of the Ballistic Missile Defense Organization. If the weapon exploded near the warhead, "you have lots of debris, and until it impacts, you aren't totally sure what's been destroyed."

Sticks and stones and atomic bombs
As you'll see from our highly non-classified sketch of the system, lots of things have to happen right for a missile defense to work.

  1. The satellite has to detect a launch -- a relatively easy task so long as enemies oblige by launching when a satellite is overhead.
  2. Getting the word back to headquarters should also be easy if electronic systems are not jammed or destroyed. But now things get a bit complicated. If the intercept is to occur over enemy territory, the commanders must order a launch almost instantaneously. That decision had best be correct, since raining missiles -- even anti-missile missiles -- on another country could cause embarrassment at best or provoke a war at worst. However, missiles emit a long plume of fire that makes a juicy target indeed.
  3. Now comes the real difficulty: launching the missiles to intercept and destroy the enemy missiles. Taking course data from satellites and radar based on Earth and ships, they must calculate the warhead's likely course before launch.
  4. Ideally, each defensive missile would target a different warhead and slam into it the first time around (with missile defense, there is no second chance). One message of the repeated test failures is that, "Just hitting anything is evidently a lot more difficult than people had hoped," says John Pike, a space analyst with the Federation of American Scientists. "It's harder than hitting a bullet with a bullet."
  5. The warheads that escape destruction continue toward their targets. Fragments of destroyed warheads and missiles would burn up in the atmosphere or hit Earth in random patterns.
How difficult is missile defense?

back more
The Why Files
There are 1 2 3 4 pages in this feature.
Bibliography | Credits | Feedback | Search

©1999, University of Wisconsin, Board of Regents.