Ron Theis still remembers sitting in his boss's office explaining why he was leaving NASA after just two years: Excessive bureaucracy, low pay, and unmotivated co-workers were among his many frustrations.
His boss, well aware of NASA's need to recruit and keep young engineers, pleaded with the recent college grad to stay - even offering to help him find work anywhere in the space agency.
"There were some really interesting projects," Mr. Theis says. "I knew it would be fantastic [at first]. Then the same stuff would grind me back down again."
Theis is now a software engineer in the private sector, and his departure from NASA represents a looming crisis for the space agency. A General Accounting Office report last year found that NASA has three times as many engineers aged 60 and over as it has 30 and under - and a quarter of its nearly 19,000 employees will be eligible for retirement in five years.
Last month, the GAO again reported the agency is having difficulty hiring people with the science, engineering, and information-technology skills that are critical to its operations.
Experts warn that when retirees walk out the door, decades of knowledge and experience will walk out with them - slowing NASA's progress and raising additional safety concerns.
"It's one of the most serious problems at NASA right now," says Wei Shyy, chairman of the mechanical and aerospace engineering department at the University of Florida.
"They need to beef up their efforts to recruit young people and increase their pay. Then they need to find a way to retain the experience of those who are leaving," he says.
The reasons behind the graying of NASA engineers are many.
First, following a major hiring spree during the Apollo moon missions, new openings were severely limited by budget cuts during the late 1980s and early '90s. Add to that the dotcom boom, which pulled many young engineers away from space exploration and into the lucrative world of cyberspace.
In response, NASA officials say they are redoubling their efforts to get young people energized about space exploration.
In addition to coaxing astronauts to visit classrooms, the agency is funding elementary school science projects, sending student experiments into space, and creating more apprenticeships for talented high schooler and internships for college students.
"The educational mandate is an imperative," NASA administrator Sean O'Keefe testified before Congress last summer. "Our mission of understanding and protecting our home planet and exploring the universe and searching for life will not be carried out if we don't have the people to do it."
In classrooms at West Ashley High School in Charleston, S.C., the excitement of "The Right Stuff" years is being rekindled.
"When you do things like this Protein Crystallization Project, which was supposed to go up on the next shuttle, that's when you see the little fireworks going off in their heads," says science teacher Jeff Taylor, referring to a NASA-funded project that allows schoolchildren to send experiments into space.
"When they do something that goes up on a space shuttle, it makes them think, 'I'm a NASA scientist,' " he says.
His students are also involved in another NASA project, which allows kids to design, build, and race their own moonbuggies at the US Space & Rocket Center in Huntsville, Ala.
"I've seen incredible growth in kids wanting to go into the sciences after having experiences like this," Mr. Taylor says. "I think you are going to see a surge of engineers in the next 10 years."
And every one will be needed, experts say. The engineering shortage has been a long-term trend. In 2000, for instance, US colleges graduated about 63,000 engineers and brought in about 25,000 from overseas.
The number of aerospace engineering degrees awarded in the US fell 47 percent between 1991 and 2000, according to a report last year by the Commission on the Future of the United States Aerospace industry
Cutbacks in defense spending led to a loss of hundreds of thousands of aerospace jobs in the 1990s, the congressionally chartered commission reported. This means fewer people are in the pipeline now as jobs in the industry open up again.
Lack of funding is only part of the problem, says William Wulf, president of the National Academy of Engineering in Washington. "The stereotype of the engineer is not very attractive, what with the whole nerd concept. But what really bothers me is that it's such an incorrect image."
He points to the 10 greatest engineering achievements of the 20th century, including electrification, automobiles, airplanes, and clean water.
Another major stumbling block to engineering careers, he says, is the way the subject is taught at colleges - heavy on math and science during the first two years. Half the students drop out not because they can't cut it, but because they just don't know what engineering is like.
"Engineering programs aren't weeding out the [bad students], they're just making it unpleasant. Students think, 'Why am I working this hard to become a nerd?' " says Dr. Wulf, who discussed this very issue with the deans of major engineering programs last week.
But Dr. Shyy at the University of Florida says his students are still very attracted to the idea of working at NASA and are willing to put up with a lot of grief to make that dream come true.
Barbara Engelhardt, for instance, had an internship at NASA while in college and then got in full-time upon graduation. She remembers the isolation in terms of age and gender, the incredible amount of bureaucracy, and the low pay - but says it was all worth it to be a part of something so significant.
"It was really exciting to think that you worked on something that would fly in a spacecraft. I would recommend the experience to anyone."
Still, Ms. Engelhardt is no longer working at NASA. She's back in school for a PhD in computer science.
For his part, Theis says he finally had to let go of his dreams of becoming an astronaut. Maybe it was the fact that it took seven signatures and two months to get a $600 valve cleaned, or that when he arrived, he was told to scrounge around for an unused computer, or maybe it was the fact that he doubled his salary when he left NASA.
"There is some amazing research being done there. I mean, you would be sitting in presentations about the composition of Jupiter's rings," he says. "But in the end, that wasn't enough."
• Staff writer Mark Clayton contributed to this story from Boston.