What's known about missile shield in Hawaii

A missile defense system yet to be tested in battle could be thrust to the forefront to protect US soil amid concerns that North Korea may be preparing a missile strike that could hit Hawaii.

An unconfirmed Japanese media report said recently that Pyongyang was considering a test-fire of its Taepodong-2 ballistic missile in early July that could be within range of the Hawaiian islands. Defense Secretary Robert Gates says the Pentagon is watching the situation "very closely" and is confident of being able to shoot down anything lobbed toward the US.

As a precaution, Mr. Gates has ordered a portable missile defense system called the Terminal High Altitude Area Defense System, or THAAD, to be redeployed on Hawaii. A sea-based sensor system known as SBX, which is designed to alert defense systems to an airstrike within seconds, is also part of the deployment.

The THAAD system is now positioned at what's called the Pacific Missile Range on Kauai, say military officials with US Pacific Command, which is headquartered in Hawaii.

"[W]ithout telegraphing what we will do, I would just say ... we are in a good position should it become necessary to protect American territory," Gates said Thursday.

The THAAD antimissile system has evolved in fits and starts over the years but it is probably up to the task, says John Pike, an expert on missile defense and director of Globalsecurity.org, a policy organization based in Washington.

"It seems to work," he says. "[I]f it were called on to intercept a North Korean warhead, it would successfully do so."

The system has been in various stages of development for about two decades. In its current configuration, THAAD travels on the back of large trucks that elevate the interceptors upward like an inverted garbage truck. The system is typically comprised of a series of such units parked at a launching area. The system has been tested five times successfully but never in combat.

The system, using a "hit to kill" capability, is designed to take out an opposing missile at the end point of its trip, within 100 miles of the THAAD launch point, Mr. Pike says. It is supposed to be able to shoot down a ballistic missile both inside and just outside the earth's atmosphere, according to the US Missile Defense Agency, which says it is "highly effective" against asymmetric ballistic missile threats and "mitigates effects of enemy weapons of mass destruction before they reach the ground."

If North Korea were to launch a missile, it would probably be from one of two launch pads about 4,900 miles away from Hawaii. The North might use the Taepodong-2, a missile that has had its fair share of problems over the years. But Mr. Pike says if the Taepodong-2 launch worked, it could certainly reach Hawaii.

But the North may only be trying to escalate tensions to obtain financial or political concessions from the international community. It has a limited number of options short of starting an all-out war with the US – something it probably wants to avoid.

"I think the North Koreans are trying to put more rungs in the escalation ladder," Pike says.