HOUSTON, Nov. 16 -- Sailing off into the orbital sunset one last time, 61-year-old astronaut Story Musgrave blasts off on his sixth and final shuttle flight Tuesday, becoming the oldest human being to fly in space.

"I think I'm right at my best," Musgrave reflected in a recent interview. "It's unbelievable, but I know darn well for certain that I'm better in my sixties than in my forties or fifties. Every single day our performance is measured. It's such a complex business, and experience does count." By that standard, Musgrave, a bald, twice-divorced father of five in near perfect shape, could easily qualify for any number of shuttle missions.

He joined NASA in 1967 and waited 16 years for his first flight, blasting off on the shuttle Challenger's maiden voyage in 1983 and taking part in the shuttle program's first space-walk. Ten years later, during his fifth mission, he led the space-walking team that repaired the Hubble Space Telescope.

He served on satellite-launching missions, including a clandestine flight to deploy a classified spy satellite, and took part in a Spacelab research mission highlighted by a dramatic engine shutdown during the climb to space.

An accomplished pilot, Musgrave has more than 17,000 hours flying time in 160 different types of aircraft -- 7,500 hours piloting high-performance jets. As if that's not enough, he has more than 500 parachute jumps to his credit, including more than 100 experimental free falls to study human aerodynamics.

And along the way, he somehow found time to pick up undergraduate degrees in mathematics and chemistry, master's degrees in business administration, biophysics and literary criticism and a doctorate in medicine.

Musgrave expects to earn two more master's degrees next year, one in the psychology of creativity and another in history. "I go to schools at night the way other people might go to a movie," he said before his fourth shuttle mission.

A walking legend at the Johnson Space Center in Houston, Musgrave is a clear standout in a world of super-achievers. But there are younger astronauts waiting their turn, an international space station to build and only so many shuttle flights to go around. And so when Musgrave was selected to join the crew of the shuttle Columbia for a 16-day astronomy and technology development mission, he was politely told not to expect another flight assignment. "Someone had to make that decision;" he said. "I can't walk away from it".

Born in Boston on August 9, 1935, Musgrave joined the Marine Corps in 1953 and served as an aircraft crew chief during assignments in Korea, Japan, and Hawaii aboard the USS Wasp. He joined Eastman Kodak in 1958 as a mathematician and operations analyst and completed a surgical internship at the University of Kentucky Medical Center in 1965.

After being selected as an astronaut, Musgrave worked on the Skylab space station project and helped develop space-walk equipment and techniques for the shuttle program.

On Tuesday at 2:53 p.m., Musgrave and four crewmates are scheduled to take off on the 80th shuttle mission. Columbia's flight will mark the sixth time in 13 years that Musgrave has flown in space, tying a world record set in 1983 by astronaut John Young.

While he claims to be afraid of shuttle launches -- "it just frightens the heck out of me" -- Musgrave clearly relishes the experience of weightlessness.

As always, Musgrave says, he will close his eyes at the moment Columbia slips into orbit and imagine stepping off a cliff to fully experience the headlong rush of free fall. "There is nothing more delicious!" he exclaims.

As always, Musgrave will carry a thick set of index cards into orbit listing interesting, educational or amusing things to do in his spare time to more fully experience the space environment. Like going to the bathroom upside down or riding the shuttle's vacuum cleaner as if it were a witch's broom. "I don't know why it wouldn't fly," he mused. "If you sit on a vacuum cleaner, and it's blowing air out one end and it's sucking on the other, you ought to propel yourself."

And as always, Musgrave will mentally send out a greeting to any aliens in the area saying, "I would like to talk. Even more, I would like you to come get me."

As his final launch approached, Musgrave was overwhelmed by a flood of phone calls, e-mail and letters from senior citizens inspired by his ongoing adventure. "It gives people immense hope", he said. "I'm having a better time in my sixties than I ever had in my twenties, thirties, forties or fifties. I'm amazed myself that life begins in your sixties. It's hard to imagine, but it's a fact."