In the early morning hours of April 12, 1981, NASA launched its first Space Transportation System, or space shuttle, mission, carrying astronauts John Young and Robert Crippen into orbit.

Fifty years after his Apollo 16 mission to the moon, retired NASA astronaut Charlie Duke says he’s ready for the U.S. to get back to lunar exploration.

Charlie Duke is part of a tiny fraternity that’s getting even smaller: People who walked on the moon.

The Apollo 16 spacecraft is dusty and home to a few cobwebs decades after it carried three astronauts to the moon.

The three Americans and one Japanese should reach the International Space Station late Monday for a five- to six-month stay, following Sunday's liftoff from NASA's Kennedy Space Center. A brief look at each:—Crew commander Mike Hopkins, 51, is an Air Force colonel and former space station resident who grew up on a hog and cattle farm in Missouri. He played football for the University of Illinois and, before becoming an astronaut in 2009, worked at the Pentagon. —Shannon Walker, 55, a Houston-born-and-raised physicist, also has lived before on the space station. She worked as a flight controller at NASA’s Johnson Space Center and then behind the scenes in the space station program, before becoming an astronaut in 2004.