Having "The Right Stuff" used to include being young. Astronauts were strapping test pilots, or eager young Ph.D.s, their heads crammed with astrophysics and acronyms. The old guys took desk jobs. Or so it seemed until Dr. Story Musgrave hit his 60s.

Dr. Musgrave and six other men and women are preparing for a 16-day scientific mission aboard the shuttle Columbia in November. And when they reach orbit, Dr. Musgrave, at 61, will become the oldest human to fly in space. An astronaut since 1967, when most of his Columbia crewmates were in grade school, he explains his longevity simply: "I love space."

Story Musgrave (his first name is an old family surname) is a Massachusetts dairy farmer's son. He recalls lying in the pastures, wondering at a starry universe that man had not yet touched. On the night before a launch, he lies in the Florida surf, watching satellites pass over and marveling at flying among them. He writes poems and fills journals about space.

Now, NASA has told him his record sixth shuttle flight this fall will be his last. The space agency won't say why, citing privacy rules. NASA spokesman Steve Nesbitt said accumulated exposure to radiation in space and bone loss due to weightlessness can factor into such decisions. But he said, "There is no age limit." Dr. Musgrave says he's "comfortable" with the decision. "Space flight is an incredible privilege and needs to be spread around among as many humans as you can," he said. Still, "I could go on and do a bunch more."

He maintains a remarkable pace and a formidable appetite for work, life and learning. Dr. Musgrave fills out his busy days with night school -- 200 credit hours in the past 10 years. Although he already holds two bachelor's degrees, three master's degrees and a medical degree, he studies philosophy, history, literature and the arts at the University of Houston. He earned a master's in literature there in 1987. The humanities offer "an incredibly rich context to look at space," he said.

He is fit enough to shrug off NASA's astronaut physicals. At 5 feet 10 and 165 pounds, he'd like to lose 10 pounds. But he runs regularly and works out 3 to 4 times a week. "I do what feels good," he said. Recently, that included 30 minutes each on a stair-step machine, a rowing machine and weight machines, plus 40 chin-ups and a brisk half-hour walk on a steeply inclined treadmill. In 29 years with NASA, he has missed two days of work.

An active pilot, he has logged 17,700 hours -- the equivalent of two years -- at the controls of 160 different aircraft. He has more hours (7,100) than anybody in a T-38 jet trainer. He holds instructor's ratings for instrument flight, gliders and airliners. He has made 500 parachute jumps -- including 100 experimental free-falls to study human aerodynamics.

He reads "piles" of books. A recent choice: "Dream of Earth," the Rev. Thomas Berry's "Eco-theology" book decrying exploitation of the planet. He also reads three news magazines a week, making notes in the margins and filing the best articles. His TV diet is lean and planned; he does not "channel surf".

While not yet a grandfather, he is the twice-divorced father of six, ages 9 to 35. He travels "all over the world" with his youngest son. Dr. Musgrave admits he tires more now. "Physically, I cannot do what I used to do. If I take some kind of hit, I'm gonna break, not bend." But "I am very blessed," he said. "I can still work around the clock without even thinking about it."

His secret? "It gets down to your philosophy of aging," he said. "My theory is if you have huge demands on you, that you live up to the demands. If you have a reason to live, you will live. If you have a reason to be mentally sharp, you will be". He has no qualms about being 60 in a game played by people in their 30s and 40s. "I'm incredibly proud of it", he said. "I'm glad to be still diving into everything I can get my hands on". Actually, he said, "I'm much better now. I know how to do the details, how to envision ahead of time what's going to be required. I am better than in my 50s."

NASA's expert on space-walks, Dr. Musgrave helped design the needed tools and equipment. He has choreographed the smallest details and contingencies for the exacting, high-risk work, and talked younger astronauts through it from Mission Control. And, he has been there himself. Dr. Musgrave's shaved head became familiar during the 1993 space-walks to repair the Hubble Space Telescope. Outside the shuttle or inside, his high, calm voice, humor and focus made the job seem routine. Baltimore-born astronaut Tom Jones, 41, who holds a doctorate in planetary science, will take his first space-walk aboard Columbia in November. "With him looking over my shoulder, we're not going to have any problems," Dr. Jones said. "My confidence has really soared. He has not throttled back in any way," the younger astronaut said. "He is not complacent. He asks very probing questions and is skeptical about many things. That makes him very valuable."

Story Musgrave joined the U.S. Marines in 1953, serving as a crew chief on an aircraft carrier. In 1958 he earned a bachelor's degree in math and statistics at Syracuse University and went to work for Kodak. A master's in business administration followed at UCLA. His interest in computers led to curiosity about the human brain and a yen for medical school. En route, he picked up a bachelor's degree in chemistry at Marietta College. His medical degree came from Columbia University in 1964, followed in 1966 by a master's in biophysics from the University of Kentucky.

When NASA opened the astronaut program to scientists in 1967, he pounced on the opportunity. "I was going to Mars," he said. "Don't laugh. Seriously, I was going to Mars." The U.S. space program was moving so fast toward the moon in 1967 that a landing on Mars within the career of a 31-year-old astronaut seemed possible, even likely. And he had to be part of it.

Space, he said, "is a physical, emotional, intellectual frontier, a way to participate fully in the universe. You could do it purely intellectually as a space physiologist or astronomer. But I wanted to put my body in it."

For 16 years, however, he remained on the ground. He helped design the Skyab space station, and devised systems and procedures for space-walks. In 1974, he began design work for the shuttle, including the space suits, air lock, and launch escape systems. Dr. Musgrave said he never lost hope of flying in space. "I was a long-term investor. I knew that would come." He finally flew in 1983, on the maiden flight of the shuttle Challenger. At 47, he had already been an astronaut six years longer than average.

More missions followed in 1985, 1989 and 1991. Then, for the Hubble mission in 1993, he was 58 and became the oldest person to walk in space. Only Vance Brand held an "older" record. At 59 in 1990, Mr. Brand became the oldest person to command a space flight. He has since retired.

At no time, Dr. Musgrave said, has NASA suggested a desk job or retirement. There have been offers from private industry. But "this [being an astronaut] is what I do. This is who I am. I'm loyal to space," he said. "I like being on the playing field, too, and people know that."

His involvement is total. Even while space-walking 368 miles above Earth, replacing parts of the bus-sized Hubble telescope, he was absorbing everything. "I have these little interrupts," he said, "and they go off all the time. I'm doing a space-walk and the interrupts say 'Look at the Earth, the sky, or inward. What are you feeling right now? Listen to your body.' It's an attempt to be a total participant, and at the same time getting the job done."

He remembers being stunned by the immense scale of the scene beyond the telescope -- the entire continent of Australia in one vast eyeful -- and by a thousand-mile auroral curtain shimmering over the night-darkened planet. "That's not something you see," he said. "It's something you feel in your stomach."

All these thoughts and far more go into his voluminous handwritten journals. At night school, for example, he keeps three parallel notebooks. "One of them is to learn that course -- "What is the philosopher saying?' The second level down is, 'What is this saying to Story Musgrave?' The third notebook down is, 'What this means to space-flight?"

Dr. Musgrave said he has not looked much beyond November's final mission. But his future is likely to include teaching or explaining space to the public. He has already helped produce several TV specials and an interactive CD-ROM computer program on geography as seen from space. "Anything would be fair game," he said. "Retirement has never been part of my thinking."