Astronaut John Young, a NASA legend who went into space six times and was on the first Gemini mission, died at age 87 late Friday after a bout with pneumonia.

Young, who was one of only 12 men to walk on the moon, was the first to fly into space six times, and he also led the first shuttle flight. In a statement, NASA Administrator Robert Lightfoot declared that the U.S. had lost a true “pioneer” of space exploration.