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Missile upgrades fly despite flaws

Published Feb. 26, 2017

WASHINGTON — The Pentagon is pushing ahead with an expansion of the nation's homeland missile defense system despite a newly recognized deficiency that affects nearly all the system's rocket interceptors, a Los Angeles Times investigation has found.

The problem threatens the performance of small thrusters attached to the interceptors. In the event of a nuclear attack, the thrusters would be relied on to steer interceptors into the paths of enemy warheads, destroying them.

If a thruster malfunctioned, an interceptor could fly off course and miss its target, with potentially disastrous consequences. The interceptors are the spine of the Ground-based Midcourse Defense system, or GMD, the nation's primary protection against a missile strike by North Korea or Iran.

The problem affecting the thrusters came to light as a result of the system's most recent flight test, on Jan. 28, 2016.

It did not go as planned. One of the interceptor's four thrusters shut down during the test, causing the interceptor to veer far from its intended course.

The U.S. Missile Defense Agency and its lead GMD contractors nevertheless touted the exercise as a success, making no mention of the malfunction.

A review board formed by the missile agency linked the failure to a circuit board that powers the thrusters. The "most likely" explanation, the panel said, was that a "foreign object" in the interceptor's internal guidance module came loose, fell onto the board and caused a short circuit.

Of the GMD system's 37 operational interceptors, 34 are equipped with older circuit boards vulnerable to the same kind of incident, according to missile defense specialists, including former and current government officials.

In flight tests, which are scripted to maximize the chances for success, GMD interceptors have failed to destroy their targets about half the time. The thrusters have been at the center of several of those failures.