WASHINGTON — Citing persistent problems in test flights, the Pentagon’s top weapons tester has recommended that the U.S. Missile Defense Agency consider redesigning the kill vehicle that sits atop the interceptors deployed to protect the United States against ballistic missile attacks.

The Raytheon-built Exo-atmospheric Kill Vehicle (EKV), designed to separate from its booster rocket and destroy incoming missile warheads by force of impact, is the business end of the Ground-based Midcourse Defense system, which serves as the primary U.S territorial shield. 

In his 2013 annual report, which was released to Congress Jan. 27, Michael Gilmore, the Defense Department’s director of operational test and evaluation, called into question the design of the EKV. “The flight test failures that have occurred during the past three years raise questions regarding the robustness of the EKV’s design,” he wrote.

The most recent intercept test of the territorial defense system occurred July 5 and ended in failure. In testimony before Congress later in July, Navy Vice Adm. James Syring, the Missile Defense Agency’s director, said initial indications were that the EKV, an older version dubbed Capability Enhancement 1, failed to separate from its booster.

The failure came after a two-year testing hiatus that was prompted by back-to-back intercept failures in 2010. The second of those failures was attributed to the EKV, which in that case was a newer variant dubbed Capability Enhancement 2. In his report, Gilmore recommended redoing the July 2013 flight test with the Capability Enhancement 1 EKV, but also suggested the MDA “consider whether to re-design the EKV using a rigorous systems engineering process to assure its design is robust against failure.”

Though already deployed and considered operational, the Boeing-built Ground-based Midcourse Defense system has a spotty record in testing, recording just eight intercepts in 16 attempts since 1999. Some of those failures have been attributed to the EKV, a complex device equipped with sensors and a multidirectional propulsion system that enable it to home in on its target.

In September, the U.S. Defense Department’s inspector general began a separate investigation into EKV quality issues.

Gilmore’s report also questioned the reliability of another MDA program, the Theater High Altitude Area Defense (THAAD) system. The interceptor system, designed primarily for overseas deployment to protect against regional threats, is capable of engaging missile threats both inside and outside the atmosphere.

“THAAD reliability and maintainability measures are still fluctuating greatly between test events, indicating system immaturity with respect to consistent reliability and maintainability growth,” the report read.

Gilmore recommended that THAAD program officials “reassess their reliability and maintainability growth planning curve.” 

Lockheed Martin is the program’s prime contractor and is under contract for five THAAD batteries with the U.S. Army. 

Mike Gruss is a senior staff writer for SpaceNews. He joined the publication in January 2013 to cover military space. Previously, he worked as a reporter and columnist for The Virginian-Pilot in Norfolk, Va. and The Journal Gazette in Fort Wayne, Ind. He...