Jack King, 81, of Cocoa Beach, Fla., was NASA's chief of media services, and had to keep reporters from around the world in line during a long string of delays leading up to Glenn's historic Friendship 7 flight on Feb. 20, 1962.
"It was a madhouse," King said Saturday.
Glenn's Friendship 7 mission and Carpenter's Aurora 7 flight three months later put the U.S. on equal footing with the former Soviet Union in a Cold War "Space Race" to the moon.
"You are the people that made it happen. And I'm so glad to see that so many of you are still around," Glenn said in a private reception with the Project Mercury veterans.
"We've sure got a lot of gray and balding heads in here," he added.
Fifty years ago, the Soviet Union was crushing the U.S. in a battle for technological and ideological supremacy.
The Soviet Union in 1957 shocked the world with the surprise launch of Sputnik, the world's first man-made satellite. Then in April 1961, Russian Air Force pilot Yuri Gagarin became the first astronaut to orbit Earth.
The U.S. countered with the launches in May and July 1961 of American astronauts Alan Shepard and Virgil "Gus" Grissom. But Shepard and Grissom only flew 15-minute suborbital jaunts into space, and the U.S. was generally regarded globally as a second-place nation.
To make matters worse, Russian cosmonaut Gherman Titov lapped the Earth 17 times during a spaceflight in August 1961.
But the orbital flights of Glenn and Carpenter followed by Mercury missions by Wally Schirra and Gordon Cooper gave the nation a sense that it could catch up with the Soviet Union and overtake them in the race to the moon.
"You know, the Mercury program changed America's image of itself," NASA astronaut Stephen Robinson told the crowd gathered in the Rocket Garden at the KSC Visitor Center on Saturday evening.
After that, people in America said, well, if we can fly into space, then we can do anything.
"So the American psyche became stronger and different because of the success of the Mercury program and the people who were in it," Robinson said.
Robinson flew with Glenn, now 90, when he returned to space in 1998 at age 77, becoming the oldest human to fly in orbit during a scientific research mission aboard shuttle Discovery.
"It's not true that NASA wouldn't let me go out on a spacewalk at my age because they were afraid I would wander off or something," Glenn said on a clear, cool, star-studded night.
In what amounted to a Space Coast version of a Hollywood premiere, Glenn and Carpenter arrived in a parade of Corvette convertibles. Photographers from around the country and Japan snapped photos of the astronauts as they walked to an outdoor stage. The only thing missing was a red carpet.
U.S. Sen. Bill Nelson, D-Fla., was there along with U.S. Rep Bill Posey, R-Fla., and space center Director Robert Cabana, who flew on four shuttle missions, including the first International Space Station assembly flight.
Cabana, a veteran shuttle mission commander and pilot, says the U.S. is getting ready to once again do great things in space exploration.
"As great as our last 50 years have been, I think our next 50 years are going to be even better," Cabana said.
Said Carpenter, now 86: "We ain't seen nothing yet."