Antonelli is the pilot of the space shuttle Discovery, which is set to launch Thursday night for a two-week mission to deliver equipment to the International Space Station.
Former teachers describe Antonelli, a member of the Class of 1985, as smart and quiet. He always wanted to be an astronaut, they said.
"That was a dream of his since he was in high school – actually, middle school," science teacher Robert Bass said.
"He was an outstanding student. He was very conscientious – just a quiet, strong student," retired English teacher Patty Driggers said.
Antonelli, who lives in Houston, studied aeronautics at the Massachusetts Institute of Technology. The Discovery mission will be his first trip into space.
"I have a lot of students who have gone on to amazing careers," Driggers said, "but there's something to being an astronaut."
Some current Douglas Byrd students said they hope one day to soar like Antonelli.
"Since I was a little kid, I've been wanting to fly. That's all I talked about," student Johnathan Gagne said. "For someone to actually follow their dreams and get it, that's big stuff."