It had been conceived as a joyous occasion, a chance to let U.S. pride soar. The six surviving original Mercury astronauts would be reunited at a gala Los Angeles dinner, and workers at the Kennedy Space Center would gather for a ceremony. At both events, speakers would celebrate the 25th anniversary of American manned space flight and chronicle the quarter-century of achievements since Alan Shepard's historic suborbital flight on May 5, 1961. After Challenger's seven crew members perished on Jan. 28, plans for a more somber observance continued; a reminder of past successes might restore NASA's morale.
Then, on April 18,...