Twelve astronauts have since walked on the moon. Robot space probes have visited every planet from Mercury to Neptune, and another is on its way to Pluto. And there has been at least one American living in space at any given time for the past dozen years; six men -- two Americans, three Russians and a Dutchman -- are today orbiting on the International Space Station.
But the United States, having retired its aging fleet of space shuttles last year, has no way at the moment to launch its own astronauts. NASA has plans for a new Space Launch System (SLS for short), and hopes private industry will take on the job of ferrying astronauts to the space station. But, for now, when the United States needs to launch an astronaut, it rents a seat on a Russian Soyuz spacecraft.
"It's unseemly to me that here we are, supposedly the world's greatest space-faring nation, and we don't even have a way to get back and forth to our own International Space Station," Glenn said during the celebrations marking the anniversary of Friendship 7.
The world was a very different place when Glenn made his five-hour flight. The Cold War was at its most chilling. The United States had been embarrassed by the first Soviet satellite and the first Soviet cosmonaut. President John F. Kennedy asked his aides if there was something -- anything -- America could do to beat the Russians in space. NASA tried, but the Atlantic floor off Cape Canaveral was littered with the wreckage of failed rockets.
America did not just need better boosters, it needed bigger heroes. It found seven: the original Mercury astronauts. And the one with whom it most fell in love was John Herschel Glenn Jr.
Fifty years ago, on Feb. 20, 1962, Glenn squeezed into his Friendship 7 capsule, circled the earth three times in five hours and became a national hero.
"Zero-G and I feel fine," he said from his spacecraft. "Man, that view is tremendous."
Historians' descriptions of the time seem almost quaint now: a nation of people fearful of Soviet attack (the Cuban missile crisis would happen eight months later), glued to their black-and-white TV sets, watching a man in a silver spacesuit climb into a tiny capsule and disappear into the sky.
It was likened to single combat. The Soviets were Goliath. Glenn was David.
"We hadn't really thought that any nation could even touch us technically," Glenn said in a 1998 interview with ABC News. "And all at once, here was this bunch of Soviets over there, for heaven's sake, outdoing the United States of America in technical and scientific things."
After the flight of the Soviet cosmonaut Yuri Gagarin in May 1961, Kennedy had committed the United States to landing a man on the moon by the end of the decade. Glenn later said he wondered at the time how NASA would pull it off.
The Atlas rocket that would launch his Mercury capsule was famously unreliable; it had blown up on several test flights.
Glenn named his spacecraft Friendship 7, honoring his fellow astronauts. He would make three orbits of the earth. His launch was scheduled and scrubbed no fewer than 10 times in four months.
Glenn did not hear him; Carpenter was not on his radio link. Instead, he felt a jolt as the rocket left the launch pad.
"Roger, liftoff, and the clock is running. We're under way."
The Atlas did not fail. Five minutes later, he was in orbit.
The nation hung on every moment of his flight -- one man, alone in the void, in a capsule so small (6 feet in diameter at the base) that he could not stretch out his arms. He reported that weightlessness was pleasant. He marveled at the "fireflies" -- later determined to be flecks of frost -- that drifted away from Friendship 7 when he rapped on the hull of the spacecraft.
Glenn was having a wonderful time. But then, trouble. As he began his second orbit, Mission Control received a signal suggesting that the heat shield, designed to prevent the capsule from burning up during reentry, had come loose. Worried controllers feared they might lose Glenn. They ordered him not to jettison the capsule's retro rockets, strapped on over the heat shield, after he fired them to descend from orbit.
The outside of the capsule heated to 3,000 degrees as the atmosphere slowed it. Glenn watched as chunks of debris flew past the window and wondered whether it was the retro pack breaking up, or the heat shield.
It held. He splashed down safely in the Atlantic Ocean. America had probably seen nothing so daring since the transatlantic flight of Charles Lindbergh.
Crowds mobbed him at a ticker-tape parade in New York. Kennedy, who saw Glenn's star power, welcomed him at the White House. Glenn returned to work at NASA and waited dutifully for another flight assignment, but the Kennedy administration had quietly let his bosses know he was too much of a national icon to risk in space again.
The Americans would gradually overtake the Soviets in space. Neil Armstrong walked on the moon in 1969. But we no longer live in the space age. And Glenn's mantle as hero has only taken him so far; a run for president in 1984 left him in debt for years.
John Glenn is 90 now, dividing his time between Washington and Ohio after a long career in the U.S. Senate. He and his wife Annie have been married for 69 years, slowed only by the inevitable maladies of age.
He did, after years of lobbying, get to fly on a space shuttle mission in 1998. He was 77 by then, arguing that some effects of weightlessness -- bone and muscle loss -- are similar to the effects of aging. While he was in orbit he said he was having such a good time that he might like another flight after that, but Annie, visibly angry, put a quick stop to that.
Glenn and Scott Carpenter, the two surviving members of the original Mercury 7 group, have been celebrated this weekend at events near Cape Canaveral, in Washington, and in Glenn's native Ohio. They have repeatedly said they hope the nation's space effort is only in a lull.
"John, thank you for your heroic effort," said Carpenter in Florida. "But we stand here waiting to be outdone."