The U.S. space agency is celebrating the 50th anniversary of the first time an American orbited the Earth.
John Glenn went around the planet three times in just under five hours on February 20, 1962, in a mission designed to see how man would react to the space environment.
The former astronaut and ex-U.S. senator took part in a forum Monday at Ohio State University to mark the anniversary and discuss NASA.
He was critical of the decision to end the U.S. shuttle program that carried astronauts to the International Space Station.
"NASA is in a difficult position today, quite frankly. It's sort of a hold-your-breath period for NASA as to what's going to happen, because the only way we go into space now, as it's already been mentioned here today, was to go over to Russia and we pay them. We buy seats for them to put our people into space on the Soyuz. And this comes at a real price because what we cannot do then is send our people up with all the equipment and everything they need to our own space station, which was developed just to do this kind of continuing research, the research in this new environment of space," he said.
American astronauts now rely on Russia to fly them into space while the United States helps fund the development of private sector spacecraft. President Barack Obama's proposed budget for next year would double the amount of money allocated to the development program to $830 million.
NASA administrator Charles Bolden was a speaker at the forum Monday. He and Glenn chatted via video link to three crew members of the International Space Station, with Glenn expressing amazement at how such a talk is now possible, considering how rapidly technology has advanced since the NASA program he was a part of decades ago.
Speaking at a NASA event last week, the 90-year-old Glenn said his experience on the historic 1962 flight is hard to describe.
"You know, the things that remain very, very personal that you can't really convey are the feelings of things and the actual feel of this and that and something and just the view [of the Earth] that was different from what people had ever been able to see before and things like that," he said.
But he was not the first person to orbit the planet. Nearly a year before Glenn's flight, Soviet Air Force pilot Yuri Gagarin made a single pass around Earth.
Glenn, who served four terms as a U.S. senator from Ohio, returned to orbit aboard a shuttle mission in 1998, becoming at age 77 the oldest person to fly in space.