It was late on the night of January 27, 1986, when Roger Boisjoly realized that something terrible was about to happen. A 47-year-old senior scientist at Morton Thiokol’s Wasatch Division, a NASA contractor based in northern Utah, Boisjoly had spent months battling his superiors, trying—with increasing desperation—to draw attention to what he had come to believe was a potentially catastrophic fault with the Challenger Space Shuttle. In the middle of a last-minute teleconference in which he had recommended that the upcoming launch, the shuttle’s 25th mission, be stopped on account of low temperatures on the pad, Boisjoly feared the worst. His managers had listened to his argument and considered his data but seemed poised to ignore him yet again.

Almost exactly a year before, during one of his regular post-flight inspections at Cape Canaveral, Boisjoly had discovered unusual charring in one of the synthetic-rubber O-rings, which sealed the joints of the massive booster rockets that helped propel the shuttle into orbit. Hot gas burning at more than 5,000 degrees Fahrenheit had apparently escaped from inside the rocket in the milliseconds after it ignited, blowing right past the seal and leaving a trail of coal-black soot in its path.

When he first glimpsed the evidence of the leak—a mixture of burned rubber insulation and traces of volatile propellant from inside the combustion chamber—Boisjoly felt his heart hammer in his chest. He was astonished that the rocket had not exploded on the launchpad, obliterating the shuttle and killing the crew. He suspected that the record low temperatures that had swept across the cape in the days before launch had stiffened and shrunk the O-rings, making them too inflexible to perform their task when the boosters lit.

Roger Boisjoly was astonished that the rocket had not exploded on the launchpad, obliterating the shuttle and killing the crew.

Gathering his samples, Boisjoly flew directly to Huntsville, Alabama, to present his findings to his bosses at the Marshall Space Flight Center, NASA’s temple of rocketry and propulsion. The meeting room was packed as he began to describe the new and alarming phenomenon he had discovered. But he hesitated to share his suspicions about what caused the leaks. He knew that if he was correct, the information would jeopardize the agency’s planned shuttle flights and, perhaps, the future of the shuttle program itself. He took a deep breath. “Guys,” he said, “you probably don’t want to hear this, but I’m going to tell you anyway. It is my technical opinion that the precipitating cause of this event was temperature.”

For a few moments, no one said a word. Then, a single voice broke the silence. “You’re right, Rog,” an unseen engineer said. “We don’t want to hear that.”

When I set out to write a narrative history of the Challenger disaster—a story that has never been told in full—I wanted to tell some of it from the perspective of the rocket engineers at Morton Thiokol who had fought to stop the launch. Central to that struggle was Boisjoly, a big, quiet man who had a reputation as a superb troubleshooter and someone who understood the engineering of the joints in the solid-rocket boosters better than anyone else.

Emotional and sometimes impulsive, Boisjoly was a newcomer at a remote plant staffed by 20-year veterans. He was principled, occasionally outspoken, and would eventually be publicly lionized for his role as a whistleblower in the investigation that followed the accident. But he succumbed to cancer in January 2012, and his memories had died with him—or so I thought.

“You’re right, Rog. We don’t want to hear that.”

I was in the third year of writing the book when, following its long pandemic closure, I finally gained access to the archives of the National Air and Space Museum in Chantilly, Virginia. There, while searching through the three file boxes of the Joseph and Susan Trento NASA Safety Investigation Collection for transcripts of interviews the veteran reporter and his wife had conducted and collated in the 1980s, I came across an unlabeled compact disc in a small, padded envelope, accompanied by a brief typed note from Boisjoly written in 1999.

The disc, more than 20 years old, seemed unlikely to be readable, let alone contain any useful information. I asked a museum archivist to take a look at it nonetheless. While I went off for a sandwich in the cafeteria, she passed the disc to the I.T. staff to see what they could find. When I returned half an hour later, she directed me to a computer at the end of the room. Open on the screen, I found a 600-page Word document: a memoir drafted by Boisjoly more than 10 years before his death but never published.

Along with the other materials Boisjoly had left behind—daily logs of his work in the structures-and-mechanics department at Thiokol, copies of internal memos and test reports—the complete memoir made it possible to follow his journey from his years as an itinerant engineer in the California aerospace industry to the months of mounting frustration and fear he felt in his office at the Utah plant as he struggled to alert his superiors to the perils of the Space Shuttle solid rockets.

Boisjoly’s alarm approached a crescendo on the morning of January 27, 1986, when he heard that temperatures in Florida were forecast to plunge to new, record lows, just hours before the scheduled launch of Challenger the next morning. He and his colleagues worked feverishly through the day to gather the data necessary to persuade NASA to stop the launch, before presenting it to them in a three-way telephone conference the night before blastoff.

At first, he thought they succeeded. But he felt his stomach churn as he listened to the managers in Alabama angrily rebut his arguments one by one. By midnight, Boisjoly’s boss had dismissed his launch recommendation. He returned home to tell his wife that his managers had made a decision that would kill seven astronauts.

In the years that followed, Boisjoly, was tormented by his failure to stop the launch. He lost his job, was diagnosed with PTSD, and was cast out from the aerospace industry. The story of how one rocket engineer became another victim of the Challenger catastrophe would have been impossible to tell without the chance discovery of an unmarked CD and the patience of the archivists in Chantilly.

Adam Higginbotham is the former U.S. correspondent for The Sunday Telegraph Magazine and former editor of The Face