As a member of the panel appointed by President Ronald Reagan to investigate the accident, Ms. Ride gained a reputation for asking tough questions. The panel learned from testimony and other evidence that there had been signs of trouble on earlier Challenger flights, but that they had been dismissed as not critical. Dr. Ride told a colleague it was difficult not to be angered by the findings.

One witness was Roger Boisjoly, an engineer who had worked for the company that made the shuttle’s rocket boosters and who had been shunned by colleagues for revealing that he had warned his bosses and NASA that the boosters’ seals, called O-rings, could fail in cold weather. The Challenger had taken off on a cold morning.

After his testimony, Dr. Ride, who was known to be reserved and reticent, publicly hugged him. She was the only panelist to offer him support. Mr. Boisjoly, who died in January, said her gesture had helped sustain him during a troubled time.

In 2003, after sitting on a shuttle-disaster panel for the second time, Dr. Ride said in an interview with The Times that part of the problem at NASA was that people had forgotten some of the lessons learned from the Challenger accident. The panel had months earlier expressed its conviction that the disintegration of the shuttle Columbia over Texas was triggered when a chunk of foam insulation fell off the external fuel tank and gashed the leading edge of the wing.

But she also said: “I flew the shuttle twice. It got me home twice. I like the shuttle.”

In 1987, Dr. Ride led a study team that wrote a report advising NASA on the future direction of the space program. The team recommended an outpost on the Moon, though not a “race to Mars.” But Mars should still be the “ultimate objective,” the group said. In the report, Dr. Ride wrote that a lunar outpost would combine “adventure, science, technology and perhaps the seeds of enterprise.” She also noted darkly that the United States had “lost leadership” to the Soviet Union in a number of aspects of space exploration.

The same year, Dr. Ride retired from NASA and became a science fellow at the Center for International Security and Arms Control at Stanford. In 1989, she became a professor of physics and director of the California Space Institute at the University of California, San Diego.

She also developed a passion for trying to interest young people, especially girls, in science, math and technology. She wrote six science books for children, including one that explained how to make a sandwich in space. (She advised eating it fast, before it floated away.)