Zero G and I feel fine ... again.

John Glenn's return to orbit adds a new chapter to the exploration of space.

For years he was part of space history. Identified with the cold war space race, clad in a silver suit in a tiny capsule he was a hero from the dawn of space flight.

When he went into space in his Mercury capsule in 1962 he uttered the famous words "Zero G and I feel fine."

This time he said he knew it was trite when he said the same thing again.

At every opportunity, before and during the flight, Glenn has said that his mission was for science.

He added that there are many similarities between the ageing process and space flight and his experiments in space may help better understand the process that all of us will go through.

Safely back on the ground

Some of Glenn's experiments into changes in his blood chemistry in orbit and into his changing sleep patterns may provide useful information, especially if his reaction to space flight differs from those of his younger companions.

But it is just as possible that the results of his experiments may be trivial.

If they are scientifically interesting they will only truly make sense if Glenn's results are compared to other astronauts of a similar age.

If Glenn is the sole data point for elderly astronauts then it will be of limited value.

On scientific grounds Glenn's flight only makes sense if other elderly astronauts follow him into space.

There are many former astronauts who would like to go into space again.

In 1972 Gene Cernan was the last man to walk upon the Moon. Having seen Glenn return to orbit he said; "I want to go. I want to get in line."

But to justify Glenn's historic shuttle flight solely in terms of science is to completely miss the point. What science there may be is a spin-off, a bonus.

Glenn's mission was overwhelmingly about space travel, about doing remarkable and dangerous things and telling us about them.

It was about one man realising a dream. It was about the dreams of all those who watched him and who dreamt that they too could one day follow him.

When was the last time so much attention was paid to a shuttle flight?

This mission was about more than science. It captured, for the first time in many years, something of the sharing of space flight, something of its heroism.

It has changed the way we all look at the final frontier. It will never be the same again.