| CAPE CANAVERAL, Florida
CAPE CANAVERAL, Florida NASA on Friday said "fear of failure" should not hold back its mission to test the boundaries of human space exploration, as the agency marked the 25th anniversary of the Challenger disaster.
Seven crew members died aboard Challenger on January 28, 1986, when a booster rocket failed 73 seconds after liftoff, triggering an explosion of the space shuttle's fuel tank.
"We who remain on the ground and asked them to fly failed them that day, as we would fail the crew of Columbia 17 years later and as we failed the crew of Apollo 1 19 years before," said Bill Gerstenmaier, who now oversees NASA's human space flight programs.
"We can't let the fear of failure stop us," he said. "The team has learned tremendous lessons from these events," Gerstenmaier told a crowd of about 250 gathered at Kennedy Space Center's Space Mirror Memorial.
"Their sacrifice was a stark, brutal reminder that our knowledge, our technology, our science and our dreams are often paid for in the dearest possible way," Gerstenmaier said.
"This has been the case throughout human history and will be the case as long as we are willing to push the boundaries of our capabilities toward destinations of which we can only dream," he said.
The U.S. space agency will be retiring its three remaining space shuttles within about six months primarily due to high operating costs and to free up funds to develop spaceships that can travel farther than the International Space Station, which orbits about 220 miles above Earth.
The Obama administration and Congress, however, have not yet finalized plans and allocated funding for follow-on work.
"GREAT THINGS SOMETIMES ... AT GREAT COST"
June Scobee Rodgers, whose husband, Francis "Dick" Scobee, was the Challenger crew commander, said that just as the accident was a transition in the shuttle program, the retirement of the fleet is not the end of human space flight, but the beginning of a new chapter.
"It's time for the next 25 years to unfold," said Rodgers, who spearheaded a drive to create a network of education centers as a living memorial to the Challenger crew, which included, for the first time, a school teacher, Christa McAuliffe.
"If we didn't somehow continue Challenger's mission then our loved ones would have died in vain," Rodgers said.
There are now 48 branches of the Challenger Center for Space Science Education in the United States, Canada, South Korea and the United Kingdom.
"Achieving great things sometimes comes at great cost," President Barack Obama said in a statement commemorating the Challenger, Columbia and Apollo 1 accidents.
"Despite the challenges before us today, let us commit ourselves and continue their valiant journey toward a more vibrant and secure future."
In addition to Scobee and McAuliffe, the Challenger crew included Michael Smith, Ronald McNair, Judith Resnik, Ellison Onizuka and Gregory "Bruce" Jarvis.
The Columbia crew -- commander Rick Husband, pilot William McCool and astronauts Kalpana Chawla, Laurel Clark, Michael Anderson, David Brown and Israel's Ilan Ramon -- died on February 1, 2003, when their ship's heat shield failed as they flew through the atmosphere for landing.
Apollo astronauts Virgil "Gus" Grissom, Roger Chaffee and Edward White died on January 27, 1967, when a fire broke out in their capsule during a prelaunch test.
(Editing by Tom Brown and Jerry Norton)