The morning was so cold that icicles lined the railings and tower of launch pad 39-B, forming a freezing fringe of ice around the Kennedy Space Center. Slowly, the warmth of the morning sun melted the ice, sending the sound of dripping water across the launch complex. At 11:38 a.m., on January 28, 1986, the space shuttle Challenger left Earth with a thunderous boom, surrounded by pillars of billowing exhaust.

Then, 73 seconds after takeoff, the propellant tank ruptured, spilling hydrogen and sparking a massive fireball. Observers who had cheered in celebration moments before could only watch helplessly as the fiery burst sent tendrils of white smoke twisting across the Florida sky. The shuttle was constructed of more than 2 million parts, assembled and tested over a decade, but its downfall lay in the brittleness of a cold, rubber O-ring seal. Just the day before, some of the project’s engineers had recommended delaying the flight, concerned that the loops of rubber wouldn’t perform properly in the cold. But their warnings went unheeded, and when the O-rings failed, hot gases leaked through one of the motor joints, bringing down the entire ship.

The disaster took the lives of seven crew members: the astronauts Michael J. Smith, Francis R. (Dick) Scobee, Ronald E. McNair, Ellison S. Onizuka, Gregory Jarvis, Judith A. Resnick, and the teacher Sharon Christa McAuliffe, who was chosen from more than 11,000 applicants for President Ronald Reagan’s “Teacher in Space” program. And with them, the ultimate goal of the space-shuttle program died, too.

Around a decade and a half before the explosion, the year 1972 marked a beginning and an end for space travel: It was the birth of the American space shuttle, and it was the last year a human walked on the moon. That year, the last of the Apollo program, polling showed that only 40 percent of Americans believed the program had been worth its hefty price tag. The cost-effective space shuttle, on the other hand, was seen as a sound investment. When President Nixon announced the shuttle in January 1972, he declared that the program “will give us routine access to space.” Unlike moon missions, which were strictly the provenance of astronauts, the shuttle flights—which Nixon described as “commutes”—open up the heavens to regular people.

The Challenger made history twice in 1983: first with the astronaut Sally Ride, the first American woman in space, and later with the astronaut Guion Bluford, the first African American. Three years later, with McAuliffe on board, the shuttle was finally poised to deliver on its promise to carry civilians into space. “Teachers in Space” was the first of many similar programs NASA had planned: Tom Brokaw, Tom Wolfe, and even a 69-year-old Walter Cronkite were among the numerous applicants for “Journalist in Space,” and the agency was considering adding an “Artist in Space” program. The ultimate goal was to send two or three civilians each year—but when Challenger was torn apart, 30 years ago, the accident changed the face of spaceflight.

The disaster meant that NASA would no longer send regular people on the space shuttle. Civilian training at the Johnson Space Center came to a halt, and flights in the so-called “vomit comet,” an aircraft whose plummeting dips allow astronauts to experience weightlessness were canceled.

For many, however, the dream of everyday space travel lingered. In 2001, Dennis Tito paid a reported $20 million to become the first space tourist, entering Earth’s orbit in the company of Russian cosmonauts and spending eight days aboard the International Space Station. His groundbreaking flight made him the first in a string of space tourists, each paying between $20 million and $40 million and inadvertently helping to spark a new private space industry.

The burgeoning world of private spaceflight received a boost in 2011, when the U.S. retired its space-shuttle program. As a result, even a ride on Soyuz, the Russian Space Agency’s spacecraft, also went off the table, as any spare seats were needed to ferry American astronauts to the International Space Station. Private industry was no longer the best way for civilians to get into space; it was the only way.

And recently, non-governmental spaceflight has made dramatic strides. In November 2015, Blue Origin, founded by the Amazon CEO Jeff Bezos, became the first company to successfully launch a reusable rocket, a feat scientists have long dreamed of (by recycling its expensive structure, the soft landing of a reusable rocket has the potential to significantly lower the costs of space travel). On January 22, Blue Origin did it a second time: The company’s New Shepard Rocket reached 333,582 feet above Earth before reigniting its boosters, hovering briefly above the ground, and then gently touching down on the launch pad.  

And this past December, SpaceX, the company founded by the entrepreneur Elon Musk, had a stunning success when its reusable Falcon 9 rocket entered orbit and then returned back to Earth intact.  (But a month later, a Falcon 9 rocket toppled and then exploded onto its landing pad on a barge in the Pacific Ocean, a reminder that spaceflight is never routine.)

There are important distinctions between the two companies: SpaceX is poised to become NASA’s workhorse, already delivering food and supplies to the International Space Station. Blue Origin, on the other hand, seems likely to join companies like Virgin Galactic and Space Adventures in their goal of sending travelers on suborbital trips.

For several of these upstart rocket companies, the ultimate goal is Mars, but they can also offer a powerful experience closer to home. Many astronauts have reported that seeing Earth from space sparks a sense of euphoric awe, known as the “overview effect,” that can be transformational. To date, only a tiny fraction of humanity has experienced this overwhelming sensation: In the 55 years that humans have been able to leave Earth, roughly 500 people have peered upon our planet from afar, taking in the glow of the planet’s atmosphere against the stark black of space.

Challenger was our first attempt to level the playing field, to give anyone that overwhelming experience. On the 30th anniversary of the tragedy, many can still remember where they were when Challenger fell, and the devastation over the lost astronauts. More difficult to contemplate is a world where Challenger had succeeded, one in which an ordinary person could don a space suit and head into the great beyond.