Sen. Jake Garn (R-Utah) told the children yesterday about hydrogen igniters and about traveling through space at 17,500 miles per hour. He spoke of his own space shuttle reentry last spring over the Indian Ocean and of the importance of sending civilians into orbit.

But, when it came time for the 350 students at Fairfax County's Stenwood Elementary School to question the visiting politician-astronaut, they didn't ask about solid rocket boosters, or about why New Hampshire teacher Christa McAuliffe died.

They wanted to know:

*"How do you avoid satellites and other space junk?"

*"What happens if the lines break when the space walkers are out?"

*And -- the burning elementary school question of the day -- how do astronauts relieve themselves in outer space?

Said Garn, in the abbreviated comment of the morning: "Gravity is very helpful."

The school invited Garn to speak last October, as a way of increasing student interest in science and technology. Garn said he considered canceling, because of last Tuesday's Challenger disaster. In the end, he decided to come.

Garn, 53, who has seven children and three grandchildren, tried to tell his very young audience how important and serious this all is. "You are the future," he said. "People like me are middle-aged, bald-headed and over the hill. The future is with you."

He reiterated his views that the National Aeronautics and Space Administration should continue to send civilians into space and he spoke of the grand poetry of the Earth, as viewed from outer space. "So remarkably beautiful," he said. The magnificence -- it just couldn't be photographed or described.

The senator had lost friends when the shuttle exploded and he was prepared for the big questions. A school display case had photographs of the dead astronauts and an inflatable model of the space shuttle hung nearby. Sometimes the toughest questions come from children.

But, for the younger ones especially -- whispering and playing with each other's hair in the darkened cafeteria -- space had a Saturday morning cartoon quality.

Yes, they knew about McAuliffe and the explosion. That seemed a long time ago, though, and so distant.

Not like this man standing in front of them, showing a color movie of himself inside the shuttle, drifting weightless in his blue NASA uniform and doing a somersault.

"You just can't imagine how much fun it is to be able to fly like Superman," the senator said, adjusting his speech slightly, as several children stretched their arms out.

One older child asked about satellites and nuclear weapons. Another wanted to know what would happen if the shuttle broke in flight. But, for many, it was all funny and unconnected to the events of last week.

Imagine -- astronauts wearing bedroom slippers. Astronauts playing with magnetic marbles, or jiggling a Slinky toy. Astronauts zooming through space like human torpedos.

Nothing, however, produced more giggles than pictures of the senator in space, attaching electrodes to his scalp to record brain waves.

"A lot of people were pleased to find out I had any," responded Garn. "In fact, a lot of people in Utah think I've been weightless from the neck up for a long time."

These children didn't know about that. The comment brought a round of hoots from the parents and teachers in the audience, but orbited thousands of feet over the students' heads.

They just thought it was most amusing -- a grownup looking so serious, sticking white Band-Aids all over his head.