The Feb. 20, 1962 launch of the Mercury project space capsule Friendship 7. Its passenger, astronaut John Glenn, became the first American in orbit.
Splashdown of Gemini 10. The July 1966 mission carried astronauts John W. Young and Michael Collins, and lasted two days and 22 hours.
Astronaut Alan L. Bean, lunar module pilot for the Apollo 12 moon landing mission, holds a container filled with lunar soil. Astronaut Charles Conrad, who took the picture, is reflected in Bean's helmet visor.
The April 12, 1981 launch of the first space shuttle, Columbia. Twenty-two years later, Columbia broke apart during re-entry; all seven astronauts aboard died.
An independent investigation board is set to release this week its final report on what caused the Feb. 1, 2003 space shuttle Columbia disaster, which killed all seven crew members aboard. But whatever NASA decides to do with the panel's recommendations, a major problem still faces the agency: setting goals for the future of U.S. space exploration. Right now, all of NASA's eggs are in one basket: the International Space Station. As NPR's Joe Palca reports, many in government say the country needs bolder goals to justify the financial and human costs of exploring space.
America's frontier spirit was showing when President John F. Kennedy decided to send a man to the moon. But some critics now say the present human exploration program is an "embarrassment" that has failed to capture the human imagination.
"It's not really exploration, it's just going around and around," says Radford Byerly, former staff director of the House Science Committee on space. "It would be like Lewis and Clark going around and around Central Park in Manhattan. Once you've been around five or 100 times, there's not much exploration left to do on that route."
Others, such as U.S. Rep. Vernon Ehlers (R-MI), say that if the goal of NASA's space program is science, manned flight is not the answer.
"Just compare the cost for example of the Hubble telescope and the incredible scientific results we got from that to the space station, which costs considerably more and is likely to produce very minor scientific results," Ehlers says.
Ehlers says the United States must decide whether the space program should emphasize exploration, or science.
A short history of the U.S. human space flight program:
Mercury: The United States entered the human space race with Project Mercury. Alan Shepard, riding in a Mercury space capsule called Freedom 7, was the first American in suborbit. He reached an altitude of 116 miles. But three weeks earlier, Soviet cosmonaut Yuri Gagarin had already become the first human to reach orbit. A year later in 1962, John Glenn, riding in Friendship 7, became the first American to orbit the Earth. The Mercury program, with a total of six manned flights, ended with a 34-hour mission by L. Gordon Cooper in May 1963.
Gemini: The spacecraft in the U.S.'s second manned space program were built for two. In 1965, the eight-day Gemini 5 mission set a new record for the longest space flight. Gemini 12, the last mission in the series, made the first automatically controlled re-entry into the Earth's atmosphere. Overall, the program involved 10 manned flights with 20 astronauts.
Apollo: The U.S. project to land a human on the moon started with tragedy when a fire broke out in the Apollo 1 spacecraft, killing all three astronauts. Each successive mission tested a new aspect required for a successful moon landing. Finally, with Apollo 11 on July 20, 1969, astronaut Neil Armstrong became the first human to set foot on the Moon. By the end of the project, 12 Americans had walked on the Moon as part of six successful lunar landing missions.
Space Shuttle: Following Apollo, NASA's goal was to fly a reusable spacecraft. The first space shuttle, Columbia, lifted off on April 12, 1981. Between 1981 and 1985, a fleet of four orbiters — Columbia, Challenger, Discovery and Atlantis — was put into service. On Jan. 28, 1986, Challenger, carrying seven astronauts, exploded shortly after liftoff, killing all aboard. On Feb. 1, 2003, Columbia disintegrated during re-entry, killing its seven crew members.