To oldly go

Yes, he was the first US space hero, he's a senator and it's great publicity, but there are very good reasons for sending 77-year-old John Glenn into orbit next week. Honestly

Next Thursday, when the shuttle Discovery blasts off from Cape Canaveral in Florida, it will be embarking on a mission unlike all the others. There will, for instance, be no space-walk for the crew of seven astronauts. The reason is simple: Nasa is afraid someone might get a tad absent-minded and wander off.

Just joking. It's true that the crew will remain confined to their quarters for all the nine days they stay aloft, but that has nothing - repeat, nothing - to do with the advanced years of one of their number. I speak, of course, of John Glenn, the first American to orbit the Earth all those years ago in 1962, and who is now destined to become the oldest person to venture into space. Glenn, in case you didn't know, is 77 years old.

There is no disrespect meant to Glenn, soon to retire as a US Senator after 24 years, that this and other unkind jibes about him have been circulating for months. What he is doing is magnificent and an inspiration to all septuagenarians who would probably even think twice before riding the big-dipper at a village funfair. But it is legitimate to wonder: is this an outing of real scientific value, an opportunity to study the ageing process in space as Nasa insists, or a publicity stunt for an agency that needs to recapture the nation's imagination?

Certainly, it gives America the chance to indulge its sentimental side. The White House announced this week that Bill Clinton will travel to the Cape to become the first President to witness a shuttle launch. And why not? It will be an occasion to uncork all the nostalgia of that February day in 1962 when Glenn triumphantly splashed down in the Atlantic after girdling the earth five times. Rewarded with ticker tape parades in an age when ticker tape still existed, Glenn joined the pantheon of real American heroes. Americans like happy endings, too. Glenn had been desperate to return to the stars but was never given the chance. Nasa wouldn't let him and eventually he left the agency, disillusioned and plunged into the much muckier universe of politics. He only discovered later that it was his old friend, John F Kennedy, who had stymied his hopes. Kennedy, apparently, considered Glenn an icon too precious to put at risk again.

The importance to America of the first Glenn mission was beyond debate. Almost a year before, in April 1961, Russia had stunned the world by achieving the first orbital flight with the cosmonaut, Yuri Gagarin. Against the background of Cold War rivalry, it was a moment of humiliation for the United States. It had to catch up and Glenn was the man who did it. National pride was regained. The achievement was immortalised in 1979 in Tom Wolfe's book, The Right Stuff, later made into a film, depicting Glenn and his astronaut colleagues on the Mercury programme that preceded the Apollo and Shuttle programmes.

Today, things are different. Russia is a partner now with America in space and, unarguably, the junior one. And the whole psychology of the space missions has changed. When Glenn first went up, the goal was straightforward: to prove that manned spaceflight was doable and, indeed, survivable. All sorts of questions attended those first voyages. Would an astronaut's eyes change shape in zero-gravity, rendering him blind? Might he gag on his own saliva? And were the heat-shields going to be enough to protect the capsule from incineration during re-entry into the Earth's atmosphere? Glenn was asking himself that even as his capsule, Friendship 7, swivelled to begin its re-entry trajectory. So were his wife and children.

There have been some equipment changes, too. In 1962, Glenn was a "Spam in the Can" astronaut, strapped tightly into his seat in a tiny vehicle with just one window and, incredibly now, not a single computer. Mission control at the Johnson Space Center outside Houston was only able to track Glenn on his orbits through teletype print-outs around the globe. Flying Discovery will be a bit different. With two million components, 950 different switches and 230 miles of wiring, it is the most sophisticated machine ever built. Also, Glenn will be able to float. He will watch the passing stars through 10 different windows and he will land, at the mission's end, on dry land.

The only time Glenn complained of feeling queasy during the Friendship mission was after splashdown when the bobbing of the capsule on the ocean made him seasick.

Glenn, who has happily noted that Discovery even has a "candy drawer" full of chocolate bars, has been in training for this mission for months. Some of it has been vigorous. He has done emergency escape drills from Houston's mock-up shuttle, dangling from ropes down its side, and allowed himself to be hoisted in a crane and dropped from high into a pool. Most of the preparation, however, has been for the scientific work. Among his duties will be collecting regular urine samples from his other crew members.

Ten experiments are set for Glenn himself, all meant to study the effects of minimal-gravity on an old person.

It was Glenn who first suggested to Nasa, three years ago, that there may be value in sending a doddering old man, or at least, a fit, doddering old man, into space. Nasa scientists long ago noted that many of the adverse effects of long periods of weightlessness mirror the changes experienced by normal people as they age. Astronauts suffer wasting of both bone and muscle tissues. Because of their disrupted circadian rhythms, they also have trouble sleeping. Anyone's grandparents will tell you about that.

"The idea is," Glenn noted recently, "will I be immune to things that happen to younger folks up there since I've already gone through the ageing process back here?" If the answer is "yes", who knows how many more 77- year-olds Nasa might be recruiting?

Nasa will go to elaborate lengths to monitor the Senator's body during the mission. He and another, younger, crew member will sleep in harnesses with a web of electrodes on their bodies to detect sleeping rhythms.

One, placed immediately beneath Glenn's nose, will record his breathing. He is even meant to swallow a gigantic pill each day, with a thermometer inside and a minuscule transmitter which will send readings to Houston. Another monitor will catch any unusual irregularities in his heartbeat.

Nobody at Nasa claims that the experiments will yield ground-breaking revelations for humanity. Glenn is not about to show us a cure for ageing. But the data, they insist, will push open the door onto a new avenue of discovery. "It's a starting point," commented Charles Layne of the University of Houston, and a former Nasa researcher. "Space flight is something, by its very nature, where data is collected very slowly."

This does not quell the criticism, however, some of it from within the astronaut community itself, that all this science is nothing more than a fig leaf so that the Senator can go on an extravagant jaunt.

A jaunt aimed at boosting public interest in Nasa and the space programme and to secure future funding for it from Washington. And a jaunt meant as a thank-you to the politician who has worked the hardest to protect that funding in the past.

Whether he is a pioneer for geriatric research or a galactic hitch-hiker taking the most expensive free-ride in history, Glenn will once more have all the eyes of America upon him next Thursday.

Listen out for these words from Mission Control at the moment of blast- off - the same words that sent him aloft in 1962: "Godspeed, John Glenn." And watch the tears of a nation well up.