"Sally lived her life to the fullest, with boundless energy, curiosity, intelligence, passion, commitment and love. Her integrity was absolute; her spirit was immeasurable; her approach to life was fearless," read a statement on the website of Sally Ride Science, a company she started to help teach students -- particularly young women and girls -- about science, math and technology.

Ride flew into orbit aboard the Space Shuttle Challenger in 1983 to become America's first woman in space. She took a second trip aboard the same shuttle one year later.

The first woman in space was Soviet cosmonaut Valentina Tereshkova, who orbited the Earth 48 times in 1963.

"As the first American woman to travel into space, Sally was a national hero and a powerful role model," President Barack Obama said soon after news of her death broke. "She inspired generations of young girls to reach for the stars and later fought tirelessly to help them get there by advocating for a greater focus on science and math in our schools. Sally's life showed us that there are no limits to what we can achieve, and I have no doubt that her legacy will endure for years to come."