The combat system has been outfitted on 84 U.S. Navy ships and 16 vessels used by the naval forces of Japan, Norway, Spain, and the Republic of South Korea. Australia is building the ships.
Though the Aegis technology is constantly tested by the Navy and is poised for deployment - should Iran fire a missile into Israel, or if North Korea launches an air attack against Japan - it has not yet been needed to intercept a hostile ballistic missile. Here is how the system works:
Aegis ship radar continuously searches 360 degrees for in-bound missiles, from the horizon into the atmosphere, said Jim Sheridan, Lockheed Martin's director of Navy Aegis programs in Moorestown.
When a missile is detected, the system computes the best trajectory and intercept point, what type of missile to send from the ship to counter the threat, and when to fire it.
"Not only do you have to hit the missile, you want to hit the payload - the front end of the missile where the bad stuff is, be it chemical, biological, or a nuclear weapon," Sheridan said.
"The system calculates the appropriate time to launch the outbound missile, so these two bullets can hit each other. The system figures out how fast the other guy is going, what direction it is going, how high it is."
Depending on distance to the target, the flight time for an Aegis missile could be three or four minutes, or up to 10 minutes.
"Maybe you let the target get a little closer before you fire," Sheridan said.
Twenty-six of the Navy's 84 Aegis ships have ballistic missile defense capability. The others perform more typical Navy missions at sea: anti-submarine warfare, targeting cruise missiles and airplanes, bombardment of land targets, Sheridan said.
"Without getting classified, the Navy is pretty smart about knowing where these threats are potentially coming from and positioning the ships in locations such that they could deal with a rogue nation threat," Sheridan said.
In February 2008, the Aegis-equipped cruiser USS Lake Erie shot down a faulty 5,000-pound defense-intelligence satellite over the Pacific Ocean west of Hawaii.
The satellite, about the size of a school bus, would have fallen on its own in early March 2008. It had malfunctioned immediately after it was launched in December 2006, and had a full tank of frozen, toxic hydrazine, similar to chlorine or ammonia.
The Navy said the fuel tank would have dispersed harmful, even potentially deadly, fumes had it fallen on land. The satellite was struck just before it reentered the earth's atmosphere.
On Friday, U.S. Rep. Mike McCaul (R., Texas), chairman of the House Homeland Security Committee, said North Korea's latest belligerence illustrated why the United States needed to expand its missile defense capabilities.
"We must remain vigilant against this escalating enemy by expanding our missile defense systems and by using sanctions to discourage these open displays of aggression," he said.
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