For many, no single word evokes as much pain.
The accident 25 years ago -- on Jan. 28, 1986 -- a scant 73 seconds into flight, nine miles above the Atlantic for all to see -- remains the National Aeronautics and Space Administration's most visible failure.
It was the world's first high-tech catastrophe to unfold on live TV. Adding to the anguish was the young audience: Schoolchildren everywhere tuned in that morning to watch the launch of Christa McAuliffe, the first teacher and ordinary citizen bound for space.
She never made it.
McAuliffe and six others perished as the cameras rolled, victims of stiff O-ring seals and feeble bureaucratic decisions.
The Day of Remembrance -- always the last Thursday of January -- has special meaning this year, and NASA paused Thursday to remember all 17 astronauts lost in the line of duty over the years.
NASA hopes to get problem-plagued Discovery flying by the end of next month. Endeavour -- Challenger's replacement -- will follow in April. It will fly with or without commander Mark Kelly, who's tending to his wounded wife, Rep. Gabrielle Giffords of Arizona, who was shot Jan. 8 in Tucson. Atlantis will close out the 30-year shuttle program with a summertime flight, No. 135.
Steven J. McAuliffe, a federal judge in Concord, N.H., and the widower of Christa McAuliffe, said in a statement Thursday that remembrances by people across the country are "both comforting and inspirational to our family."