Some students at Hutchison Elementary School obviously had prepared for their first face-to-face meeting with an astronaut.

Michael Clifford, age 10, who described himself as "very intrigued by model rocketry," phrased his one question carefully: "In the event of an RTLS abort, what happens to the SRBs?"

Kathryn Thornton took a deep breath and explained in perfect astronaut lingo that after the shuttle is launched, a malfunction may cause controllers to order a "return to launch site" (RTLS) abort. When this occurs, she said, the solid rocket boosters (SRBs) initially propelling the shuttle will burn until they fall off, then the shuttle makes a computer-guided U-turn and glides to a safe landing at the launch site.

As she initiated the "Young Astronauts" program in the Herndon school last week, Thornton explained the mechanics of the space shuttle slowly and answered dozens of children's questions patiently. Her visit was part of the nationwide school program that provides a special space curriculum and field trips to encourage students to explore science careers.

One of the first inquiries, "Why did you want to be an astronaut?" was easy to answer. "It sounded like a lot of fun," Thornton said, adding that she was "surprised" when she was chosen from among 5,000 applicants. "It just seemed like it would be a great challenge. And I was right."

Thornton completed a year of astronaut training in June and expects to make her first space shuttle trip within 18 months. She is the 13th woman trained in the program and works in Houston alongside Sally Ride, who made news as the first American woman in space.

"What was the best thing" about Thornton's training? The astronaut said she especially liked her brief taste of weightlessness when, in zero gravity, "it feels like swimming but you don't change directions until you bounce off something."

Discussion of the airtight space suit and helmet was fascinating to the pupils, who wanted to know how a person eats, sneezes or scratches while confined. Those making the moon missions had special hoses built in for drinking water or nibbling on a fruit bar, Thornton said, but they were generally "out of luck" on sneezing and scratching.

Space shuttle astronauts, however, fly in the comfort of shorts, T-shirts and socks, she said, because they do not leave the spacecraft.

"What if the steering wheel breaks?" was answered with a description of the "fail op, fail safe" system, which provides a backup for virtually every spaceship mechanism, then gets the shuttle home safely if all reserves fail.

The food samples Thornton showed -- compact see-through pouches containing freeze-dried lemonade, "Italian vegetables" and cookies -- looked foreign to the youngsters, who responded with a chorus of "yuck" and "eeuw."

What is the astronaut most afraid of? Not Martians or meteors or aborted missions, she said, but "press conferences."

Thornton, 33, has a 3-year-old daughter and another child due in a month. She said she planned her pregnancy carefully to avoid conflict with her career and that she continues to participate in all training exercises except flying T38 jets.

The native of Montgomery, Ala., stopped by the school on a trip to her home in Charlottesville. Thornton received a master's and PhD in physics from the University of Virginia.