“Do we have concerns about morale?” he asked. “Yes, we always do. Do we have concerns about the welfare of our workers? Yes, we always do.”

But Mr. Bolden, a retired Marine Corps general, said his workers were excited not only about the Atlantis mission but also about a range of new endeavors at both the space agency and its commercial partners.

“We’re trying to help our people stay in the aerospace industry, if not in NASA,” he said while denying any paralyzing loss of talent. “We’re capturing the brainpower.”

And he flatly rejected the idea that the agency had lost its way.

“We’re not adrift,” he said. “And the vision is not gone. And we have a plan. We have a very sound plan.”

History has offered some bleak lessons, with tons of wreckage testifying to the danger. Experts say the Team B effect contributed to disasters in the mid-1980s and late 1990s that destroyed more than a dozen rockets, wiped out billions of dollars in satellites and threw the nation’s unpiloted space program into turmoil. The two catastrophes of the space shuttle program — in 1986 and 2003, which killed 14 astronauts — had more to do with design flaws and management failures than with depleted ranks of experts.

NASA officials say close examinations of failures and problematic retirements have made the agency smarter. “We went out and looked at who has done this well — and who has not,” said Bryan D. O’Connor, NASA’s chief of safety and mission assurance.