For more than 30 years, Bob Ebeling carried the guilt of the Challenger explosion. He was an engineer and he knew the shuttle couldn’t sustain the freezing temperatures. He warned his supervisors. He told his wife it was going to blow up.

The next morning it did, just as he said it would, and seven astronauts died.

Since that tragic day, Ebeling has blamed himself. He always wondered whether he could have done more. His daughter, Kathy Ebeling, said he had even entertained bringing his hunting rifle to work  Jan. 28, 1986 to threaten NASA not to launch — that’s how certain he was that the shuttle was going to explode.

30 years ago, the Shuttle Challenger exploded during launch while CNN broadcasted on live television. All seven crew members were killed. (Jenny Starrs/The Washington Post)

That day changed him, Kathy Ebeling, who was 35 then, said in an interview. He became despondent and withdrawn. He quit his job not long after, unable to face it — the  MURDERER in graffiti on the overpass on his ride to work, the constant reminder of how NASA failed. He spent the rest of his working life on a bird refuge because there it was about “helping people and not destroying people,” she said.

He’s 89 and is dying now. He has bladder and prostate cancer; the family has brought in hospice. But thanks to hundreds of public radio listeners, he finally has some peace.

Bob Ebeling (Courtesy: Kathy Ebeling) Bob Ebeling (Courtesy: Kathy Ebeling)

Ebeling spoke to NPR for the 30th anniversary of the Challenger explosion last month. Remarkably, he had spoken anonymously to the same reporter three weeks after the explosion, but now he was ready to speak publicly. He sadly recalled the day and described his three decades of guilt.

“I think that was one of the mistakes that God made,” Ebeling told NPR. “He shouldn’t have picked me for the job. But next time I talk to him, I’m gonna ask him, ‘Why me? You picked a loser.’ ”

But listeners didn’t hear a loser. And they sent hundreds of e-mails and letters to NPR and directly to Ebeling telling him so, NPR first reported Thursday.

His daughter, reached at their Utah home, said she’s been reading him the letters. Engineering teachers said they use him as an example of good ethical practice. Professionals wrote that because of his example they are more vigilant in their jobs.

But there was one person that made him finally start to believe he wasn’t to blame.

Allan McDonald, who was Ebeling’s boss, reached out after the NPR interview aired to tell him that he had done everything he could have done to warn them, including calling Kennedy Space Center to try and stop the launch.

And a spokeswoman for NASA Administrator Charlie Bolden sent a statement commending courageous people like Ebeling who “speak up so that our astronauts can safely carry out their missions.”

“It’s wonderful, it’s like a miracle,” Kathy Ebeling said. “It’s starting to change his mind that he doesn’t feel so guilty, so that’s a miracle. Thirty years of guilt is long enough.”

He told NPR that his “burden,” while not totally gone, was “certainly reduced.”

Howard Berkes, the NPR reporter who has known him for three decades, wrote that “Ebeling is now more buoyant than at any time I’ve seen or talked to him in the past 30 years.”

“Dad, have these letters helped you in finding your peace?” Kathy Ebeling said she’s asked him. He told her, “yes.”

“He doesn’t have to die with this nagging guilt,” she said. “He can die free.”