Hagel acknowledged a problem with the guidance system of missile interceptors and said further testing would occur this year.

CNN: U.S. to beef up missile defense against North Korea, Iran

He acknowledged a problem with the guidance system of missile interceptors and said further testing would occur this year.

CNN: U.S. to beef up missile defense against North Korea, Iran

Lockheed Martin received a contract in 2007 to extend the life of the missiles until at least 2040, with additional contracts doled out to upgrade the guidance system and refurbish the nuclear warheads the missile carries.

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Building that larger missile would require major advances in metallurgy, rocket engines, guidance and propulsion, and probably foreign assistance.

CNN: Commentary: North Korean launch not a cause for panic

The NRC guidance divides the lower 48 United States into three regions as to wind speed, missile size, depressurization, etc.

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