After years of nagging, the 77-year-old senator has persuaded NASA to allow him back into space. On Thursday, he will blast off on Discovery, becoming the oldest person ever to go into orbit. In space, no one can hear you wheeze.

And as just as surely as he floats into zero gravity, so he will step firmly into controversy.

By putting Glenn into the vanguard of the Viagra generation, NASA has left itself wide open to the accusation of gimmickry.

Superficially, the goals of Glenn's mission are laudable. Bodily changes caused by space flight -- wobbliness, falling over, and loss of bone marrow and motor co-ordination -- mirror those of ageing, and led NASA and the US National Institute on Ageing to set up a joint study in 1989. Glenn's flight is theculmination of that collaboration.

But few observers are convinced. They say his 140-plus orbits on Discovery will merely be victory laps, a sentimental nod to the past that points out just how boring the space programme has become since the Apollo moon landings. ``In the late twentieth century, the only thing that will get public interest in the space programme is the sort of celebrity politics that Hollywood plays and everybody plays,'' says Duke University's Alex Roland, a former NASA historian. ``That trivialises whatever the hell it is that is going on on shuttle flights.''

It is a point backed by retired NASA engineer Homer Hickam Jr. ``It is a telling comment that all we can do for John Glenn is carry him back into low-Earth orbit as we did in 1962. That's still all we can do.'' Part of the problem stems from the fact that the full results of Glenn's geriatric research may never be made public. NASA usually conceals the identity of astronauts when medical data is published. But in the case of Glennthere is only one elderly test subject, and he has so far refused to sign a waiver to release of medical data that would be linked with him. ``NASA keeps the physical data private and I favour that,'' he said.

But if Glenn's results are not made public it will only fuel criticism that his mission is no more than a public relations gimmick, says Rick Tumlinson, president of the Space Frontier Foundation. And he has a point. When Glenn made his flight on the Mercury Freedom 7 capsule 36 years ago, his medical read-outs were public knowledge. His heartbeat and blood pressure charts from that flight, which can be seen on the Internet, show that in 1962 the astronaut's heart rate peaked during his three orbits of Earth at 114 beats per minute. In 1998, it is likely to remain confidential.

-- The Observer News Service