When Sally Ride flew aboard the shuttle Challenger on June 18, 1983, she won a place in American history as the first American woman in space, a role she accepted with mixed feelings.

"It's too bad this is such a big deal," she said at one preflight NASA news conference. "It's too bad our society isn't further along."

Dr. Ride, who died of pancreatic cancer on Monday at her home in San Diego at the age of 61, returned to space in October 1984 on an eight-day mission that included a second female astronaut, Kathryn Sullivan, who became the first woman to perform a spacewalk.

Dr. Ride, a physicist, was also, at 32, the youngest American in space at the time of her first mission. Dr. Ride became the only person to sit on both panels investigating the catastrophic shuttle accidents that killed all astronauts on board — the Challenger explosion in 1986 and the Columbia crash in 2003.

Dr. Ride was finishing studies at Stanford — degrees in physics and astrophysics (and also English) — and looking for a job when she saw a newspaper advertisement that said NASA was accepting astronaut applications. She looked at the qualifications and said, "I'm one of those people," she told The New York Times in 1982. "The women's movement had already paved the way, I think, for my coming," she said.

But there were still rough spots. Before the first shuttle flight, Dr. Ride — chosen in part because she was known for keeping her cool under stress — politely endured reporters' asking whether spaceflight would affect her reproductive organs, whether she planned to have children, whether she would wear a bra or makeup in space, whether she cried on the job, how she would handle menstruation in space. On "The Tonight Show," Johnny Carson joked that the shuttle flight would be delayed because Ride had to find a purse to match her shoes.

The Soviets had already sent two women into space. One was welcomed aboard a space station by a male cosmonaut who told her the kitchen and an apron were ready for her.

Dr. Ride switched from physics to engineering and helped develop a robotic arm for the space shuttle. The Challenger commander, Robert Crippen, chose her for the 1983 mission in part because of her expertise with the device. At Cape Canaveral, many in the crowd of 250,000 that watched the launch wore T-shirts that said, "Ride, Sally Ride."

The next day, Gloria Steinem, then editor of the magazine Ms., said, "Millions of little girls are going to sit by their television sets and see they can be astronauts, heroes, explorers and scientists."

When the shuttle landed, Dr. Ride told reporters, "I'm sure it was the most fun that I'll ever have in my life."

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. Dr. Ride wrote that a lunar outpost would combine "adventure, science, technology and perhaps the seeds of enterprise." She also noted darkly that the U.S. 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 University. 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.)

In 2001 she started a company, Sally Ride Science, to "make science and engineering cool again," as she put it, by providing science-oriented school programs, materials and teacher training.

Dr. Ride was known for guarding her privacy. She rejected most offers for product endorsements, memoirs and movies, and her reticence lasted to the end. At her request, NASA kept her illness secret.

Dr. Ride was born in Encino, Calif., to a father who taught political science at Santa Monica College, and a mother who worked as a volunteer counselor at a women's correctional facility.From an early age, she gravitated toward math and science, and also competed in tennis while at Westlake High School, a girls' prep school in Beverly Hills, where she found a mentor and friend in Elizabeth Mommaerts, a science teacher whom she described as "logic personified."

Dr. Ride attended Swarthmore College in Pennsylvania but quit after three semesters to go to Stanford, where she played tennis and was nationally ranked. She received bachelor's degrees in physics and English in 1973 (her specialty was Shakespeare), a master's degree in physics in 1975 and a doctorate in astrophysics in 1978, all from Stanford. Her graduate work involved X-ray astronomy and free-electron lasers.

Dr. Ride married a fellow astronaut, Steven Hawley, in 1982, and was divorced in 1987. Dr. Ride is survived by her partner of 27 years, Tam O'Shaughnessy; her mother, Joyce; and her sister, Scott, who is known as Bear.

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