Yet they and everyone else who has gone into space have shared both the knowledge of and anxiety over the risks involved -- including the fact that more than a few other missions nearly resulted in disasters.
Columbia's crew included commander Rick Husband, 45, of Amarillo, Texas; pilot William McCool, 41, of San Diego, Calif.; mission specialist Michael Anderson, 43, of Spokane, Wash.; mission specialist Kalpana Chawla, born in Karnal India, who earned her Ph.D. from the University of Colorado; mission specialist David Brown, 43, of Arlington, Va.; mission specialist Laurel Clark, 41, of Racine, Wis.; and payload specialist Ilan Ramon, 48, the first astronaut from Israel.
The seven were part of an elite field of only 370 individuals selected by the National Aeronautics and Space Administration in 18 groups over the years for its space programs. The process began on Oct. 7, 1958 with the pursuit of the original Mercury astronauts, who were expected to demonstrate America's superiority in space over the Soviet Union.
On Apr. 9, 1959, the Mercury group -- also seven -- made its public debut: Scott Carpenter, L. Gordon Cooper, Jr., John H. Glenn, Jr., Virgil I. "Gus" Grissom, Walter M. Schirra, Jr., Alan B. Shepard, Jr. and Donald K. "Deke" Slayton.
Shepard was the first American to be launched into space, making a brief sub-orbital flight on May 5, 1961. Grissom followed with a similar flight on July 21, although an accident at splashdown caused his Liberty Bell 7 capsule to be lost at sea and Grissom, whose spacesuit was weighted down with souvenirs he had smuggled aboard, nearly drowned.
John Glenn's Friendship 7 capsule was launched into a planned seven-orbit flight on Feb. 20, 1962, but an onboard sensor warned that the spacecraft's heat shield had come loose, so Glenn was ordered to land after only three orbits.
Scott Carpenter's Aurora 7 craft also orbited three times, but a navigational error caused NASA some anxious hours before the capsule was found. On national television, a tearful Walter Cronkite intoned, "We may have lost an astronaut."
Three years before he walked on the moon, Neil Armstrong, along with astronaut Dave Scott, nearly died when a malfunctioning thruster placed their Gemini 8 capsule in a wild spin. Only seconds before blacking out, Armstrong fired the capsule's main engine and halted the spin.
NASA's most famous near-miss came on Apr. 13, 1969, when an oxygen tank exploded onboard the Apollo 13 spacecraft, setting off a heroic effort by the three astronauts -- Jim Lovell, Jack Swigert and Fred Haise -- and NASA's ground controllers to devise ways of bringing the crippled craft home and keeping its three occupants alive.
Two years earlier, NASA had experienced its first fatal accident when the Apollo 1 space capsule caught fire during tests on its Kennedy Space Center launch pad on Jan. 27, 1967. Astronaut Grissom was killed, along with Edward White and Roger Chaffee.
The first moon landing, accomplished by Apollo 11 on July 20, 1969, came perilously close to disaster. The lunar excursion module, named "Eagle" by the crew, was within 10 seconds of running out of fuel and crashing into the moon's surface before Armstrong and fellow crew member Edwin "Buzz" Aldrin, Jr., managed to find a safe place to set the craft down, in an area called the Sea of Tranquility.
On Jan. 28, 1986, shuttle Challenger exploded 73 seconds after liftoff, killing its crew of seven: commander Francis Scobee, and crew members Michael Smith, Judith Resnick, Ronald McNair, Ellison S. Onizuka, Gregory Jarvis and Christa McAuliffe, a teacher chosen to be the first of her profession to go into space.
Although all of America's space disasters have received immediate and widespread publicity, many similar incidents in the former Soviet Union took place in secret. For example, in 1963, a Soviet rocket engine failed to fire. When technicians arrived at the launch pad to correct the problem, the engine suddenly fired, causing a massive explosion and killing as many as 200.
Perhaps the most succinct view of what must run through every astronaut's mind just before liftoff was delivered by Michael Collins, the third member of the Apollo 11 crew, who stayed in orbit aboard the "Columbia" command module during Armstrong and Aldrin's mission to the lunar surface.
Asked what he was thinking as he sat atop the giant Saturn 5 rocket, Collins replied: "Well, you think about the fact that you are at the top of 6 million parts, all made by the lowest bidder."
As to why, despite the fear and the risks, people continue to go into space -- and eagerly -- the reasons are perhaps best addressed by Onizuka, Hawaii's first astronaut and the first Asian American in space, who was lost aboard Challenger.
"Every generation has the obligation to free men's minds for a look at new worlds," he said, "to look out from a higher plateau than the last generation."
(Editors: UPI photos WAX2003020102, WAX2003020103, WAX2003020108, KSP2003011601 and KSP2003011602 available)
Notable deaths of 2014 [PHOTOS]