WASHINGTON — The U.S. Defense Department continues to experience delays and failures with components aboard its space and missile defense systems due to a shortage of qualified technical personnel and a general inattention to detail, two top Pentagon officials said.

The problems run across the enterprise, from the government work force, to the prime contractors, to the subsystem parts suppliers, these officials said.

In satellites and launch vehicles, the U.S. Air Force continues to uncover hardware and software issues, often during the final phase of integration and testing, said Gary Payton, deputy undersecretary of the Air Force for space programs. The work force in recent years has also been prone to testing errors that have added to the long delays many military space systems have experienced.

“We have been finding during assembly, integration and test problems on satellites and on launch vehicles,” Payton said during a Feb. 4 media event here sponsored by the Space Foundation. “Valves on launch vehicles, gyroscopes and reaction wheels on satellites, [these are where] we’ve been finding problems. Also we’ve been finding test execution problems in the clean room.”

The problems stem from a young and inexperienced work force that is replacing experienced engineers and scientists from the baby-boom generation, Payton said. But it is also related to the methods by which the government builds and tests its systems, which during the 1990s and early 2000s strayed from the fundamentals that were a staple of previous decades, he said.

“We have reinstated very, very rigorous prelaunch test regimens that we did in the ’70s and ’80s that we kind of forgot to do in the ’90s,” Payton said. “We’re discovering the problems before launch, but that makes our assembly, integration and test period longer than it should be. It’s not as bad as it was four, five or six years ago, but it’s still worrisome. Every single program was running across piece-part problems, and we don’t have that breadth of problems anymore.”

Payton said it is not that the current space work force is less talented than the prior generation, but that there are fewer people coming into the field. The Air Force’s primary space hardware shop, the Space and Missile Systems Center, lost more than a third of its work force during the late 1990s and early 2000s, and the service is now trying to rebuild that work force. It will add about 900 civilian and military contracting and engineering personnel over the next few years, he said.

Meanwhile, quality control problems on ballistic missile defense systems are rampant and have resulted in delays in fielding the capabilities for warfighters, according to David Altwegg, executive director of the U.S. Missile Defense Agency (MDA). He placed the blame on MDA contractors across the board, saying the root cause is a “lack of attention to detail. Missilery is all about detail.”

“I am excusing no one from this conversation,” Altwegg said during a Feb. 1 media briefing here. “I’m not going to name names today, but I’m going to tell you we continue to be disappointed in the quality that we are receiving from our prime contractors and their subs — very, very disappointed.”

Altwegg described a December intercept test of the Terminal High Altitude Area Defense System in which a target missile was deployed from a cargo plane. The target dropped through the sky and its booster was supposed to ignite at an altitude of about 6,000 meters, but instead he watched it fail to ignite and drop into the Pacific Ocean.

“Subsequent analysis [by the] Failure Review Board disclosed a big-time quality problem,” he said. “That’s the most recent example.”

Altwegg would not rule out quality issues as a culprit in the failed test Jan. 31 of the Ground-based Midcourse Defense system. Though an initial MDA statement placed the blame on the Sea-Based X-band radar, which was being used for the first time as the primary cuing tool for the interceptor, Altwegg said it was premature to finger any particular part of the system. Another Failure Review Board has been convened, and it will probably be months before an exact cause of the failure is determined, he said.

The MDA in recent years has created a quality control organization that now has about 130 employees embedded at many of its contractors’ facilities.

“We are working this problem assiduously,” Altwegg said. “We conduct two-week, in-plant reviews of those contractors that we feel are having difficulty. … We are interested in helping them get well, but we continue to have quality problems.”