Pentagon Shoots Down Mock Warhead Over Pacific in Defense Test |

The Pentagon says it has shot down a mock warhead over the Pacific in a success for America's missile defense program.

The test was the first of its kind in nearly three years. And it was the first test ever targeting an intercontinental-range missile like North Korea is developing.

The military says an interceptor rocket launched from Vandenberg Air Force Base in California slammed into the warhead as it traveled outside the Earth's atmosphere after being launched from a test range on a Pacific atoll.

The Pentagon is still incorporating engineering upgrades to a missile interceptor that has yet to be fully tested in realistic conditions.

North Korea says its nuclear and missile programs are a defense against perceived U.S. military threats. Its accelerating missile development has complicated Pentagon calculations, most recently by incorporating solid-fuel technology into its rockets. The step would mean even less launch warning time for the United States. Liquid fuel is less stable and rockets using it have to be fueled in the field, a process that takes longer and can be detected by satellites.

While Tuesday's test wasn't designed with the expectation of an imminent North Korean missile threat, the military will closely look for progress toward the stated goal of being able to reliably shoot down a small number of ICBMs targeting the United States. The Pentagon is thirsting for a success story amid growing fears about North Korea's escalating capability.

Laura Grego, senior scientist at the Union of Concerned Scientists, which has criticized the missile defense program, calls the interceptor an "advanced prototype," meaning it is not fully matured technologically even if it has been deployed and theoretically available for combat since 2004. A successful test Tuesday, she said, may demonstrate the Pentagon is on the right track with its latest technical fixes.

"Overall," she wrote in an analysis prior to the test, the military "is not even close to demonstrating that the system works in a real-world setting."

The interceptors are, in essence, the last line of U.S. defense against an attack by an intercontinental-range missile.

The Pentagon has other elements of missile defense that have shown to be more reliable, although they are designed to work against medium-range or shorter-range ballistic missiles. These include the Patriot missile, which numerous countries have purchased from the U.S., and the Terminal High-Altitude Area Defense, or THAAD, which the U.S. deployed this year to South Korea to defend against medium-range missiles from North Korea.