(Updates with reaction)
* Ride was astronaut aboard space shuttle Challenger in 1983
* She was also physicist and author of children's science books
* President Obama calls Ride "a powerful role model" (Updates with quotes from Ride's former husband)
By Irene Klotz
CAPE CANAVERAL, Fla., July 23 (Reuters) - Sally Ride, the first U.S. woman to travel into space and an advocate for science education, died on Monday after a 17-month battle with pancreatic cancer, according to her organization, Sally Ride Science. She was 61.
Ride broke new ground for American women in 1983 when at the age of 32 she and four male crewmates blasted off aboard space shuttle Challenger.
"The fact that I was going to be the first American woman to go into space carried huge expectations along with it," Ride recalled in a 2008 interview on the 25th anniversary of her flight.
"I didn't really think about it that much at the time -- but I came to appreciate what an honor it was to be selected," she said.
U.S. President Barack Obama called Ride "a national hero and a powerful role model." In a statement, he said Ride "inspired generations of young girls to reach for the stars."
Ride was not the first woman in space. That distinction fell to the Soviet Union's Valentina Tereshkova, who blasted off aboard a Vostok 6 rocket on June 16, 1963.
But over the years only two other Russian women followed Tereshkova into orbit.
By the time Ride returned for a second flight in 1984, not only had another female astronaut, Judith Resnik, flown on the shuttle, but Ride had a female crewmate, Kathryn Sullivan.
Since then, more than 45 women from the United States and other countries have flown in space, including two as shuttle commander.
"Sally Ride broke barriers with grace and professionalism - and literally changed the face of America's space program," NASA administrator Charles Bolden, a former astronaut, said in a statement.
Ride grew up in Los Angeles and attended Stanford University, where she earned bachelor's degrees in physics and English and master's and doctorate degrees in physics. She joined NASA's astronaut corps in 1978.
She was assigned to a third shuttle flight, but training for the mission was cut off after the fatal 1986 Challenger accident that claimed the lives of six colleagues and a schoolteacher.
Ride served as a member of the presidential commission that investigated the accident, and then assisted the agency's chief with long-range and strategic planning.
She left NASA in 1987 and joined a Stanford University security research institute. In 1989, she joined the physics department at the University of California-San Diego and directed the California Space Institute.
Ride's interest in education extended to younger students, whom she targeted with her science education startup Sally Ride Science in San Diego.
The company creates science programs and publications for elementary and middle school students and educators.
Ride also authored science books for children and served on dozens of NASA, space and technology advisory panels, including the board that investigated the second fatal space shuttle accident in 2003.
Her former husband, Steve Hawley, an astronaut who left NASA in 2008, said in a statement that Ride was a private person who never became fully comfortable with her celebrity status.
"Sally Ride, the astronaut and the person, allowed many young girls across the world to believe they could achieve anything if they studied and worked hard," said Hawley, who now teaches astronomy at the University of Kansas.
"I think she would be pleased with that legacy," he said.
Ride is survived by her mother; her partner, Tam O'Shaughnessy; a sister; a niece and a nephew. (Additional reporting by Dan Burns; Editing by Kevin Gray and Lisa Shumaker)