ORLANDO, Fla. — A little more than a minute after launch and high above Kennedy Space Center, shuttle Challenger was ripped apart after failure of a rubber seal allowed a spurt of rocket flame to ignite the spacecraft’s giant fuel tank.

The roiling plume of Challenger’s disintegration would sear an image in the nation’s psyche that spoke of a particular sorrow; among seven astronauts killed 30 years ago Thursday was teacher Christa McAuliffe.

“We will never forget them,” said President Ronald Reagan in a broadcast hours later evoking triumph from tragedy. “The Challenger crew was pulling us into the future, and we’ll continue to follow them.”

But if Challenger’s meaning seemed clear then, today nearly half the nation is too young to remember the loss or hadn’t been born when it happened. Time has taken a toll on the emotional impetus from America’s first loss of astronauts in flight.

Challenger’s legacy also may have lost relevancy in a nation struggling now to figure out the future of human spaceflight.

Howard Lieb, a New York dentist who lives part time in The Villages in Central Florida, remembers Challenger’s fate vividly and, as a father, has not forgotten the faces of McAuliffe’s parents in news photos.

At the time of the disaster, he said, there was national will to try again and do better, to embrace Reagan’s inspiration that “nothing ends here; our hopes and our journeys continue.”

But the country changed as the shuttle program played out its 30 years, he said.

Today, “there is no redemption to the tragedy,” Lieb said. “We’ve begun to look at such risks as unacceptable.”

How Challenger lessons will serve the nation’s next era in space remains unclear. NASA has neither funding nor a spacecraft to deliver astronauts to Mars any time soon.

More immediately pressing for the nation’s space endeavors is the rise of the commercial rocket business. Cape Canaveral saw 17 rockets launched last year, marking a 12-year high. The launch count is expected increase this year.

Private, billionaire-led companies like Elon Musk’s SpaceX and Jeff Bezos’ Blue Origin have helped restore excitement around space exploration, which waned when the shuttle program ended in 2011.

But at the Challenger Center for Space Science Education, the tragedy is far from forgotten. The center, founded in 1986 by the families of the astronauts who died, has expanded to more than 40 schools, universities and museums.

“When you enter a Challenger Center all of them have pictures of the crew on the walls,” said Lance Bush, the nonprofit organization’s president. “When children come in to get their briefings, they are told about these heroic individuals.”

Families of the seven-member crew in the shuttle Columbia accident in 2003 have added their support to Challenger Center, which has had more than 4.4 million students.

“It’s important to have programs like this that inspire adventure and discovery,” said Laura Husband, 25, daughter of Rick Husband, commander during Columbia’s ill-fated flight.

Speaking to the lessons of Challenger, Roger Launius, associate director of the Smithsonian’s National Air and Space Museum in Washington, D.C., said NASA’s aura of invincibility collapsed with the disaster.

“Hubris is always a problem, and every Greek tragedy is built around that,” Launius said. “It was valid 2,000 years ago and it’s still valid today.”

After Challenger exploded, NASA pledged to redesign the shuttle’s flawed rockets and remake the agency’s approach to safety.

But after Columbia disintegrated during re-entry 17 years later, the investigator of that disaster said NASA’s safety discipline was “perfect” on paper only.

“When you bore down a little bit deeper, you don’t find any there, there,” retired Adm. Harold Gehman said then. “There’s no people, money, engineering, expertise, analysis.”

Bob Crippen, a Florida resident who was a pilot during the first shuttle flight in 1981 and flew three more times as commander, said important lessons of Challenger and Columbia remain valid today.

NASA struggled to communicate internally on critical concerns and did not respond adequately to information arising from damage to rocket parts during spaceflight, lapses that may be even harder to thwart with commercial launches, he said.

“NASA doesn’t have the same degree of control and isn’t able to observe contractors as closely as previously,” Crippen said.

Crippen noted that SpaceX and Orbital Science Corp. suffered disasters with unmanned rockets during the past two years, which should provide a valuable learning experience.

Alex Roland, professor emeritus of history at Duke University and former NASA historian, said NASA’s vulnerability at the time of the accidents was huge bureaucracy and intense political pressures, causing the agency’s guard to slip.

He said that leaner, private companies presumably would not be as vulnerable to the failures behind Challenger and Columbia.

“But I’m not so sure,” Roland said. “I think they experience a lot of the same pressures because they are trying to get renewals and increases in their NASA contracts.”