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The engineers knew. They'd already warned NASA and Utah's Morton Thiokol that the O-ring seals on the solid rocket boosters that hoisted space shuttles skyward could fail catastrophically with a terrible loss of life.

But late on the night before the Challenger launched on Jan. 28, 1986, the engineers were overruled. The next morning, it took about 73 seconds before everything they had predicted came to pass. O-rings failed, the shuttle's huge liquid fuel tank exploded, and five men and two women plummeted 60,000 feet to the Atlantic Ocean.

As everyone involved would learn, the matter was not just a technical problem. It was a failure of leaders and managers under immense pressure to launch on schedule. All that would lead to an epic demonstration of the power of blowing the whistle on the disaster that happened 25 years ago Friday.

Allan McDonald, director of Morton Thiokol's shuttle solid rocket booster (SRB) project near Brigham City, was at Kennedy Space Center for the launch. He and other engineers worried that cold weather would compromise the O-rings.

The summer before, he'd briefed NASA bigwigs that the O-rings were the biggest safety issue on the shuttles. He wanted a redesign — a proposal rejected for being too expensive.

That January, McDonald, Roger Boisjoly and other engineers argued that any launch at a temperature below 53 degrees would be dangerous. During the early morning hours of Jan. 28, ice coated parts of the launching pad.

So McDonald and other Morton Thiokol engineers and scientists met with NASA program directors late on Jan. 27. In the end, McDonald's boss recommended going ahead with the launch. NASA wanted the recommendation in writing.

"It was the smartest thing I ever did. I refused to sign it," McDonald said Tuesday. "I forced my boss to sign it."

The next morning, it was 38 degrees outside.

"We expected it to blow in the [launch] tower," he said. "It happened 73 seconds later."

As it turned out, McDonald would be joined by Richard Cook, a NASA lead resource analyst for the solid rocket booster program, in blowing the whistle.

Then-President Ronald Reagan convened the Rogers Commission to investigate. McDonald, convinced that senior NASA and Morton Thiokol managers were attempting a cover-up, was not invited to testify.

But sitting in the audience at a commission teleconference, he spoke out, telling commission Chairman William Rogers that he and the other engineers had advised against the launch. He would learn later that Jesse Moore, the NASA boss with final say on the launch, had never learned of their fears.

McDonald ended up testifying. To protect himself, he also made a point of writing down everything he'd heard, done, said and learned about the launch.

Meanwhile, Morton Thiokol demoted him, putting him in charge of scheduling.

"What the hell was I supposed to schedule?" he asked.

At the same time, Cook assembled NASA information on the boosters' design flaws. He said he went through several channels, "including Rogers and NASA management," but no one was interested.

So he went to The New York Times and spelled out everything he had. That led to the newspaper's so-called "O-ring Papers" report in early February of that year.

"The whole thing just suddenly exploded," Cook said Wednesday. "NASA continued to backpedal, but it was too late."

Cook believes that Reagan was involved, too. Because teacher Christa McAuliffe was aboard Challenger — and Reagan was to deliver his State of the Union address focusing on education — he needed the shuttle aloft.

McDonald disagrees.

"There's nothing to any of that," he said.

In the end, the Rogers Commission blamed the disaster on failures in communication and misleading information, as well as a conflict between engineers and managers and their judgments.

Cook went straight from NASA to the U.S. Treasury Department.

Under pressure from some members of Congress who threatened to strip Morton Thiokol of NASA contracts, McDonald was assigned to lead the redesign of the solid rocket boosters, which took nearly three years.

Both have written books: McDonald's Truth, Lies and O-Rings and Cook's Challenger Revealed.

They've also teamed up to teach management principals and ethics this week at California's Chapman University.

One key: "People need to stand up and give their professional opinion, even in a hostile environment," said McDonald, who lives in Salt Lake City. "Leaders need to create the same forum. ... We need to take fear out of the situation."

Cook added, "Exercising authority through power is the enemy of good management."

Both see parallels between the decision to launch Challenger and the management decisions that led to the Gulf of Mexico oil spill. An independent safety team on the deepwater well warned BP that the rig would blow.

But "BP was not paying attention to them," Cook said.

The safety team hired a helicopter to whisk them away before the blast killed 11 people and damaged the Gulf for what could be forever.

I've been managed, and I've been a manager. I know how hard it is to speak up when you think you're right and have the evidence to prove it. But maybe, just maybe, you'll be the one to avert the worst.

Peg McEntee is a newscolumnist. Reach her at The Challenger disaster online

• A NASA transcript details the final minutes captured by the Challenger's audiotape.

• President Reagan's Challenger disaster speech:

• Video of the Challenger explosion: