Young, AE 52, had six space flights — seven counting a liftoff from the moon — and was commander of the first shuttle mission that began the modern era of space travel.

Young, 74, said he intends to remain actively involved in the space program as a consultant and he plans to continue attending astronaut staff meetings. He is eager for space exploration to develop a base of operations on the moon and later Mars.

Development of a moon settlement — a base for exploration and mining the moon's resources — could be of great benefit to Earth, he said. Because of available sunshine, it would be possible to pipe reliable, uninterrupted electrical power back to Earth.

"We ought to be looking at alternative energy sources," Young said.

Young joined the National Aeronautics and Space Administration in September 1962 as a member of the second astronaut class.

Young's career as an astronaut has been dazzling. He's been to the moon twice and is one of only a dozen astronauts to have walked on the lunar surface. He flew in the Gemini, Apollo and space shuttle programs and is the only astronaut to pilot four different spacecraft.