Waiting out this frustrating postponement at the cape, Ed Corrigan, Christa's father, said wryly, "I would have gotten the hacksaw sooner." Commented his wife Grace: "I would have gotten my nail file." One veteran consultant to NASA was less charitable, asking, "Can you imagine a pad leader permitting an s.o.b. to show up for work with a drill with a dead battery?"

That night, temperatures fell to an unseasonable 27 degrees , but the wind dwindled to 9 m.p.h. On Tuesday, Jan. 28, the clear morning sky formed what glider pilots fondly call "a blue bowl." Even before Challenger's crew, wearing gloves against the chill, crossed the access arm to take their assigned places, NASA's "ice team" had inspected the shuttle and its towering gantry. They decided that there was no danger of any icicles breaking away on lift-off and harming the heat-shield tiles. Just 20 minutes before the scheduled lift-off, they made another check. A Rockwell engineer in California, watching by closed-circuit TV, telephoned the cape to urge a delay because of the ice. But Kennedy Space Center Director Richard Smith, having been advised that there was little risk, permitted the countdown to continue.

"We're at nine minutes and counting," intoned NASA Commentator Hugh Harris over the cape's public address system. His words were also broadcast widely by radio.

Shivering reporters, photographers, schoolchildren and other spectators cheered. The countdown was past the point where it had stopped the day before. The mission designed to show that space belonged to everyone finally seemed ready to launch both its schoolteacher and the dreams of the children participating vicariously from their schools. On Challenger's flight deck, roughly the size of a Boeing 747's, Scobee and Smith continued to run through their elaborate checklists. The orbiter's main computer, supported by four backups, continuously scanned all the data from some 2,000 sensors and data points. They would shut down the entire system in milliseconds if anything was wrong. Nothing was.

"T minus eight minutes and counting."

Thousands of motorists in the cape area, listening to their radios, pulled off highways and faced the ocean. On Challenger's middeck, Onizuka, Jarvis and McAuliffe had nothing to do except wait. At dozens of points around the globe, radar tracking stations had now synchronized their antenna systems with the countdown sequence in Florida.

"T minus seven minutes, 30 seconds and counting."

The walkway was pulled away from Challenger. It could be repositioned within 15 seconds, but in an emergency that could be a fatal interval. The seven occupants were now wedded to their three combustible companions. One was the rust-colored external tank, 154 ft. high, which carried 143,351 gal. of liquid oxygen and 385,265 gal. of liquid hydrogen. Two lines connected the fuels to the orbiter, where they would be mixed at controlled levels to power the spacecraft's engines. The other two companions were the gleaming white boosters, each 149 ft. tall and packed with more than 1.1 million lbs. of solid fuel. Once ignited at lift-off, they would burn uncontrollably until their fuel was spent.

"T minus six minutes and counting."

Pilot Smith was given the order to prestart the auxiliary power units that would operate Challenger's control surfaces and swivel its engine nozzles. The last pints of oxygen were pumped into the external tank.

"T minus four minutes and counting." Mission Control reminded the flight crew to close the airtight visors on their helmets.

"T minus three minutes and 30 seconds." Now the shuttle was operating totally on its own internal electrical power system.

"T minus two minutes and 20 seconds," Harris announced. "No unexpected errors reported."

The Harris announcements were coming more frequently. Everything looked good.

"Ninety seconds and counting. The 51-L mission ready to go." The best news yet: the many delays for Challenger's crew seemed at an end.

"T minus 45 seconds and counting."

The launch platform was about to be flooded by powerful streams of water gushing from six pipes fully 7 ft. in diameter. The purpose: to damp the lift- off sound levels from Challenger's three engines. Otherwise, the acoustic energy alone could damage the craft's underside. The main-engine firing sequence was turned over to computers.

"T minus ten ... nine ... eight ... seven ... six ... We have main- engine start."

Even then the onboard computer, sensing the slightest glitch, could still abort a launch. As it happened, Resnik had been aboard the shuttle Discovery in June 1984 when, four seconds before the spacecraft's three main engines were to ignite for lift-off, the computer noted that the thrust from one of them was not at the proper level. The fuse was immediately pinched.

"Four ... three ... two ... one ... And lift-off. Lift-off of the 25th space shuttle mission. And it has cleared the tower." Like runners passing a baton, Harris handed off the public narration to Steve Nesbitt, the communicator at the Johnson Space Center in Houston. At the cape, his voice was lost amid the cheers of some 1,000 spectators watching on bleachers some four miles from Pad 39-B. Even at that distance, they could feel the power of the blast-off, which elicits an almost instinctive elation. A graceful sculpture arising from an awesome explosion: it was just as it was supposed to look. Among the relieved viewers were relatives of most of Challenger's crew, including Christa's parents and her husband Steven. At Concord High School, students who had repeatedly gathered in the auditorium finally had a chance to blow their party horns and cheer their teacher's loftiest achievement.