The last time John Glenn flew in space, he was 40 years old. His Mercury space capsule had 56 toggle switches, 143 cockpit displays and no on-board computers.

When the shuttle Discovery leaps off the launch pad this week, with a 77-year-old Glenn strapped in below decks, pilot Steven W. Lindsey will command five computers, and a dashboard crammed with 856 toggles and 2,312 displays.

This is not your grandfather's spaceship. And fortunately for all on board, the World War II fighter pilot -- born six years before Charles Lindbergh made the first solo flight across the Atlantic -- will not be flying it.

Nor will he deploy the Spartan solar observatory, test equipment to be used in the next servicing mission to the Hubble Space Telescope, or help with observations of Jupiter by the International Extreme Ultraviolet Hitchhiker.

But NASA officials insist that the four-term Ohio senator and space hero is not just along for the ride, or even for the avalanche of nostalgic publicity his nine-day swan song will surely generate.

Glenn, they say, is riding the rocket to provide valuable new data on the troublesome biomedical effects of prolonged spaceflight. Astronauts lose muscle and bone mass in space. Their sleep is fractured, their hearts shrink, their immune systems weaken, and they wobble and faint when they try to stand up after landing.

0 It's called "space adaptation syndrome," and

it has been a focus of study for years. Countermeasures must be found before humans can fly safely to Mars, or live for months or years on space stations.

Always alert for terrestrial applications that might help justify their work, space scientists are also intrigued by parallel declines they see among the elderly.

"It's thought that by understanding what's going on in astronauts' bodies, and how it reverses itself [after landing], that this information can be applied back on Earth in understanding the changes in bodies as they age," said neuroscientist David Liskowsky, the Discovery mission's life sciences program scientist.

Orbiting septuagenarian

Enter John Glenn. Until he asked to fly, all NASA's test subjects have been astronauts ages 30 to 55. After three years of his nagging, the National Institute on Aging and other NASA consultants finally agreed that an orbiting septuagenarian could introduce new variables to help sort out the effects of weightlessness and aging.

"Doing research is like doing a jigsaw puzzle," Liskowsky said. "You need all the pieces to complete the puzzle. And this is one of the pieces, certainly."

Glenn is a sample of just one weightless senior citizen, with limited statistical value. But David Williams, director of space and life sciences at the Johnson Space Center, said his responses may provide new insights, new questions, and perhaps more geriatric astronauts.

He may be unique, said NASA spokeswoman Eileen Hawley, but Glenn had all the required training, and "is being treated the same as any other payload specialist."

After blastoff, set for 2 p.m. Thursday, Glenn will take his turns preparing meals and cleaning up the shuttle cabin. He'll shoot video of the Earth and on-board activities. And, he will help start, monitor and stop 15 of the mission's 83 experiments.

"We're using him as an extra pair of hands," said mission flight director Phil Engelauf.

But the senator will be the flight's top guinea pig. The mission's life-sciences Web page features his picture alongside those of the experimental toad fish and cucumbers flying with him.

Glenn doesn't mind. If it leads to better health care, he told a recent news conference, "I look at being a guinea pig as being a compliment."

He'll swallow a "body core" thermometer, and don a suit of sensors during four nights' sleep. They'll transmit 21 data streams, on brain wave activity, heart function, breathing, blood oxygen, muscle activity and more.

His sleep patterns will be studied closely and compared with those of younger astronauts and the earthbound elderly. In orbit, astronauts' internal "body clocks" are often scrambled by a new sunrise every 90 minutes. Similar sleep disturbances often come with aging, leading to waking often and early and leaving us less attentive and more nap-prone during the day.

Glenn was to have taken doses of the brain hormone melatonin, to see if it worked as a sleep aid for astronauts. But NASA dropped him from that study for undisclosed medical reasons.

John Glenn's veins will be tapped so often that he refers to Scott Parazynski, the physician/astronaut who'll wield the needle, as "Igor."

His blood and urine will be analyzed for stress-related hormonal changes and protein losses that may cause muscle breakdown. Mineral imbalances may signal bone loss triggered by weightlessness. Similar losses are seen among the sedentary elderly, or anyone immobilized by illness or injury.

Glenn's blood may also reveal a weakening in his immune system, a temporary problem noted by prior astronauts. Doctors are interested in parallel symptoms among the elderly.

Returning astronauts often get dizzy and wobbly when they return to Earth's gravity, problems caused by temporary changes in the inner-ear and in blood pressure regulation. Similar changes among the elderly -- often permanent -- are responsible for many falls. Glenn will undergo two weeks of tests after landing to record how well his balance and blood pressure return to normal.

Baltimore study

Glenn will be compared with 280 people in Baltimore, who will undergo the same battery of tests beginning in January. It's a part of the National Institute on Aging's continuing Baltimore Longitudinal Study of Aging. The 30-year-old project follows subjects throughout their lives, gathering valuable data on the aging process.

But if there is scientific value in putting aging astronauts in space, why has NASA said yes to Glenn, while disqualifying such veterans as Story Musgrave, who was cashiered from the flight list two years ago, at 61?

NASA would not say why Musgrave was grounded. But while age alone does not bar astronauts from space, officials said, such things as accumulated exposure to radiation and weightlessness might. Musgrave flew a record six shuttle missions.

Now retired from NASA, Musgrave has said Glenn's flight makes history and good public relations sense for the space agency.

"But we need to be honest about it," he said. John Glenn is not a scientist or a career astronaut. "We are flying a legislative passenger, as we have in the past. It's John Glenn. Marvelous. But it is a legislative passenger."

Eileen Hawley, the NASA spokeswoman, said Glenn is more than a passenger. He's a fully trained payload specialist. "They are typically not career astronauts," she said. They are more likely to be astronomers, or doctors, or engineers.

"They fly for specific tasks, and that's the case for John Glenn. But he's got previous experience that most don't have. He's got experience working as a member of a team. He has military and NASA experience. He understands the chain of command and has insights into how space flight works."

From marines to space

Glenn had most of that before his crew mates were born.

He joined the Marine Corps in 1941, right after the bombing of Pearl Harbor. He was 20, a small-town kid from New Concord, Ohio who went to war instead of medical school.

A Marine aviator, he flew 59 combat missions in the Pacific during World War II. Years later in Korea, he flew 63 more missions, downing three MIGs in the final nine days of the conflict.

After Korea, Glenn attended the Test Pilot School at the Patuxent Naval Air Station in Maryland. Chosen in 1959 as one of the nation's first seven astronauts, Glenn was the third to fly, but the first to orbit the Earth.

On Feb. 20, 1962, his cramped Mercury capsule circled the planet three times in 4 hours and 55 minutes. After splashing down in the Atlantic, the capsule went to the Smithsonian Institution, and Glenn emerged to media stardom and ticker-tape parades.

But President John F. Kennedy feared that NASA might lose its wholesome, handsome hero, and Glenn was blocked from further space flights.

In 1964 he quit the agency. He spent nine years in private industry before winning one of Ohio's U.S. Senate seats. (He is stepping down this year. His successor will be elected Nov. 3. Glenn, who will likely be in orbit, voted by absentee ballot.)

Glenn never stopped hoping to return to space, even after twice becoming a grandfather. He pushed his scientific case for flying and let NASA figure out what his stature and celebrity could do for the space program.

NASA has flown politicians before. Republican Sen. Jake Garn of Utah flew in 1985, and Rep. Bill Nelson, a Florida Democrat, went up in 1986. The practice stopped after the Challenger accident, but Glenn persisted.

Staying fit

He kept himself fit. He shuttled between Washington and Ohio every week, flying his own twin-engine plane, and even set a speed record in 1996. He lifted weights and took brisk two-mile walks every day near his Maryland home.

Asked recently if he could keep up with the grueling pace of life on the shuttle, he said flatly, "Yes."

Besides, space flight isn't as grueling as it used to be.

Take legroom, for example. Glenn's Mercury capsule was no bigger than a Volkswagen Beetle. He was stuffed into a helmeted space suit and strapped down in just 36 cubic feet of habitable space. If shuttle crew members each got as little, Discovery could fly 64 people into orbit. Instead, seven shirt-sleeved astronauts will have 2,325 cubic feet to float in.

Riding his Atlas rocket in 1962, Glenn was crushed into his seat by nearly 8 "Gs" -- acceleration forces nearly eight times that of gravity. Discovery will glide him to orbit with a relatively gentle 3 Gs, and land like an airliner.

Space travelers are a more diverse lot than the military test pilots of Glenn's era. Only three of Discovery's crew (including Glenn) have been test pilots. Two are physicians, and two hold Ph.Ds. Four are engineers, two are foreigners and one is a woman. All but one are space veterans.

Of the veterans, Glenn has logged the least time in space. Commander Curtis L. Brown, who was 5 during Glenn's historic flight, has logged 997 hours on four prior shuttle missions.

The next oldest crew member is Chiaki Mukai, 46, a Japanese physician with a Ph.D. in cardiovascular surgery. The youngest, Pedro Duque, 35, will become Spain's John Glenn -- the first from his nation to orbit the Earth. An aeronautical engineer, he had not been born when Glenn flew in 1962.

"Slight risk"

NASA officials said Mukai and Scott Parazynski, 37, a physician who specialized in emergency medicine, are not on board because of fears Glenn might be stricken in orbit.

"There is a slight increased risk" in sending a 77-year-old into space, NASA's Engelauf said. The agency reviewed all its procedures and practices to see what needed to be changed for Glenn, but "we haven't come up with anything."

The risk, he said, is balanced by the knowledge to be gained.

Just the same, mission controllers will make sure the crew gets its sleep and a half-day off. And Discovery will carry all the customary emergency and life-support gear, including a cardiac defibrillator. But then, all this fretting over the risks to Glenn misses the point of space exploration, said Scott Carpenter, 73, also one of NASA's original Mercury astronauts.

"Those of us who ride these machines, John Glenn included, are expendable, and for good cause," said Carpenter, still clearly possessed of "The Right Stuff."

L Told of the remark, Glenn said, "I've got to talk to Scott."

Pub Date: 10/25/98