“I could go over to the Hill and put pressure on people above me and get something done,” Mr. Cantrell explained about his success in Washington. “With the Army, as long as the senator is not calling over and complaining, everything is O.K. And the senator will not call over and complain unless the contractor you’re working with does not get his money. So you just have to keep the players happy and it works.”

The national missile defense program has cost the United States more than $110 billion since President Ronald Reagan unveiled his Star Wars plan 25 years ago. Today, the missile defense effort is the Pentagon’s single biggest procurement program.

The Army declined to discuss the Cantrell case, other than to say it had taken steps to try to prevent similar crimes from happening again.

But some current and former Defense Department officials say the exploiting of the system that preceded Mr. Cantrell’s kickback scheme has had a damaging impact, slowing progress toward building a viable missile defense system by diverting money to unnecessary or wasteful endeavors. That pattern of larding up the defense budget with pet projects pushed by lawmakers and lobbyists is a familiar one.

“What they did may have been a scandal,” said Walter E. Braswell, Mr. Ennis’s lawyer, referring to the actions of his client and Mr. Cantrell. “But even more grotesque is the way defense procurement has disintegrated into an incestuous relationship between the military, politicians and contractors.”

Dr. J. Richard Fisher, one of Mr. Cantrell’s former bosses, said: “The system needs to change. But it is not likely to do that. There is just too much inertia  and too much self-interest.”

Getting Around the System

Towering over the highway near the entrance to Huntsville is a replica of the Saturn V rocket, the powerful missile that lifted the first man to the moon.