Just before noon on January 28, 1986, people watched with excitement as the space shuttle Challenger lifted off from its Florida launch pad -- but that excitement and hope soon turned into horror.
Just seventy-three seconds after liftoff, Challenger exploded, killing all seven astronauts on board.
One of its crew members was Christa McAuliffe, a school teacher from New Hampshire who had won a national competition to become the first teacher in space.
The goal was to boost interest in space exploration among American school children, many of whom were watching the Challenger's launch live on television or in person.
"We were all outside and the kids were all standing around and all of sudden we saw the smoke break into the Y shape," said Kari Anna Roy, who was in fourth grade at an elementary school in Lutz, Fla. "The teachers immediately knew something was wrong and rushed us back inside."
Roy said it took a while for her and her fellow classmates to grasp what happened.
"There was a teacher on board and we had been very excited about it and talking about it in school for a long time," she said. "It was a pretty devastating kind of thing especially for a school and we had all directly seen it happen right there."
Kevin Baron, now a reporter for Stars and Stripes, said that his Orlando elementary school watched every shuttle launch.
"We were in the lunchroom when the principal came in to tell us to turn on all the TVs," Baron said. "We walked outside into the field and the smoke trail was still coming down. We spent the rest of the day in school watching TV."
Jen Vargas also watched the launch from her Orlando elementary school.
"It was right before lunch, we were standing out there watching the shuttle go up. Usually it just goes straight up and it kind of veered off to the right. A lot of kids were confused, I was confused," she said. "We were crying and upset because we knew we had just seen the astronauts walk out and wave into the crowd and everything, and then we see them go up and the explosion happened.
The horrifying image of that massive fireball in the sky was replayed endlessly on television and burned into Americans' memories.
President Ronald Reagan was scheduled to deliver his State of the Union Address that night, but the White House postponed the speech and instead the president tried to comfort a grieving nation.
"We will never forget them, nor the last time we saw them, this morning, as they prepared for their journey and waved goodbye and ``slipped the surly bonds of earth'' to ``touch the face of God," Reagan said in what was perhaps the most memorable speech of his presidency.
Reagan also spoke directly to the nation's school children.
"I know it is hard to understand, but sometimes painful things like this happen. It's all part of the process of exploration and discovery. It's all part of taking a chance and expanding man's horizons," he said. "The future doesn't belong to the fainthearted; it belongs to the brave. The Challenger crew was pulling us into the future, and we'll continue to follow them."
The Challenger explosion not only dealt a major blow to the nation's psyche, but also to NASA. The shuttle program was grounded for nearly three years in the wake of the disaster as NASA investigated its cause. Ultimately, the investigation proved that the disaster could have been prevented.
John Pike, a national security analyst and space specialist, said NASA still has not recovered from the Challenger disaster.
"I think it's clear that NASA today is a consequence of the Challenger accident, because prior to the accident NASA had a confidence about where it was going and its ability to get there that it simply doesn't have today.
"NASA has no idea where it's going and is tremendously confused about how to get there."
In 2004, after America lost a second shuttle, Columbia, President George W. Bush announced the retirement of the aging shuttle fleet by the end of the decade -- after nearly 30 years and more than 100 missions -- and the development of a new, more modern space exploration vehicle.
"Our current programs and vehicles for exploring space have brought us far, and they have served us well," Bush said. "It has been used to conduct important research and to increase the sum of human knowledge."
Last year, President Obama announced a new direction for the nation's space program, scrapping plans to send another astronaut back to the moon and instead focusing efforts on reaching Mars.
Obama came under considerable fire in recent weeks for his decision to cancel the Bush administration's plan to send an American manned mission to the moon for a seventh time.
Obama insisted he was 100 percent committed to NASA's mission and future.
"For me, the space program has always captured an essential part of what it means to be an American -- reaching for new heights, stretching beyond what previously did not seem possible," Obama said last April to an audience of several hundred astronauts, engineers and members of the NASA community at the Kennedy Space Center near Cape Canaveral, Fla. "And so, as president, I believe that space exploration is not a luxury, it's not an afterthought in America's quest for a brighter future -- it is an essential part of that quest."
Just two or three more space shuttle launches remain -- Discovery, which is scheduled to launch on Feb 24; and Endeavour, which is scheduled for April 19. A launch of Atlantis is timelined for June but is not yet funded.
Astronaut Mark Kelly, the husband of Rep. Gabrielle Giffords, is scheduled to command the Endeavour mission.
Just as President Reagan promised in the hours after the tragedy, Americans still remember the Challenger and its crew. This week, the seven astronauts were honored at memorial services at Johnson Space Center in Houston and at Arlington National Cemetery in Virginia.
Today, there are nearly 50 Challenger Learning Centers worldwide, where hundreds of thousands of school children are encouraged to reach for the stars.