Missile Defense Test Hits Target, But Not Off the Hook Yet

June 25, 2014
Laura Grego
Senior Scientist

The Pentagon announced that the Ground Based Midcourse (GMD) test FTG-06b on Sunday was successful.

It is likely to take a few months to sort through all the data and to see in detail what went right and what went wrong.  However, at some point soon, the Obama administration will need to make some decisions about the GMD system, and one of them is what to do about the 14 new interceptors it has stated it plans to build. Raytheon is apparently standing at the ready to provide some more CE-II kill vehicles. According to a Reuters article, Wes Kremer, vice president of air and missile defense systems at Raytheon said, “There are no other hurdles that we’re aware of, so we expect that we will go into production shortly.”  Reuters also reports that the Defense Comptroller, the Pentagon’s top financial official, said that he “think[s] our plan now remains to buy the original 14 interceptors.”

However, when the Secretary of Defense Hagel announced the plan to buy 14 interceptors by 2017, he said this would be on the condition that the U.S. “fly before we buy,” requiring that “we have the complete confidence that we will need.” And Congress will have its say, as well.

This success doesn’t let the Missile Defense Agency off the hook—while Sunday’s success must have been a needed boost of confidence for the missile defense team, since they were able to identify and find a mitigation scheme for the inertial guidance system problem revealed in FTG-06a, it tells us very little about the reliability of the fleet of fielded interceptors or the CE-II kill vehicle. It certainly isn’t close to providing the “complete confidence” that Sec. Hagel called for. A 1 in 3 record might be acceptable for the developmental stage of a system, but it is not acceptable for a system on which one wants to depend.

Using multiple shots to improve confidence is only a good strategy if the effectiveness of each shot is uncorrelated. But if there is a problem common to all the kill vehicles—a “common-mode failure”—then if one fails due to that problem the others are likely to as well. In that case firing more interceptors doesn’t necessarily increase the kill probability. So far at least two of the failure modes of the interceptors have been common, such as the problem with the CE-IIs inertial guidance system in FTG-06 and the problems with the batteries uncovered in last summer’s FTG-07 CE-I test.