"It's hit-to-kill technology," said Rick Lehner of the U.S. Missile Defense Agency. "What it does is, you're colliding the kill vehicle directly with the warhead, and just the sheer force of the collision happens very high in space."
Tests of the technology, however, have shown problems with the interceptors and their effectiveness in taking down another missile. While the Alaska interceptors have never been tested, the ones at Vandenberg have been tested with about a 50 percent success rate.
"We've had 15 tests, and eight have had successful intercepts. Seven did not, but of those seven only three were actual misses and the other four came from problems with quality control or software issues," Lehner said.
"Based upon what we learn from the failures, we've incorporated fixes into the silos in Alaska and California," he said. "We have very, very high confidence in their ability to perform."
Congress has also asked the Defense Department to look into placing a missile defense system on the East Coast, though Lehner insisted that the Alaska base would be able to protect the entire country from a missile attack.
As rhetoric from North Korea has grown more belligerent in recent weeks, missile defense systems around the world are prepared for any kind of launch, according to the Department of Defense. That includes defenses against short- and mid-range missiles aboard battle ships in the Pacific as well as radar and ground systems in Japan and Guam.
But the interceptors at Fort Greely are specifically designed for long range missiles, known as an Intercontinental Ballistic Missile or ICBM, currently in development in North Korea and Iran.
The Defense Department believes that North Korea was testing one such ICBM when it launched a rocket in December that North Korea press described as a space launch.
"We believe they're testing their ICBM," said Lt. Col. Cathy Wilkinson of the Secretary of Defense's office. "That's why the international community objected to the December launch."
If North Korea developed the ability to launch a nuclear warhead on an ICBM, the interceptors would need to be ready, the Defense Department said.
The time between a missile being launched to the interceptors needing to be fired would be "minutes," Scott said.
"We know that they have an ICBM program, and we know that they are pursuing a nuclear program," Wilkinson said.