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.

(SpaceX via AP)CAPE CANAVERAL, Fla. Its back to the future as NASA astronauts launch again from the U.S. aboard a retro-style Right Stuff capsule. SpaceXs Dragon crew capsule outshines NASAs old Apollo spacecraft in virtually every way. This fresh take on a vintage look will be on full display Wednesday when SpaceX plans to launch NASA astronauts Doug Hurley and Bob Behnken to the International Space Station a first for a private company. Russias workhorse Soyuz capsules, still in use after a half-century plus, have kept NASA astronauts flying to the space station. A test dummy soloed on last years Dragon crew capsule debut.

(SpaceX via AP)CAPE CANAVERAL, Fla. The two astronauts who will test drive SpaceXs brand new rocketship are classmates and friends, veteran spacefliers married to veteran spacefliers, and fathers of young sons. Retired Marine Col. Doug Hurley will be in charge of launch and landing, a fitting assignment for the pilot of NASAs last space shuttle flight. Hurley, 53, and Behnken, 49, are NASAs first test pilot crew in decades. Crippen and the late John Young rode NASAs first space shuttle, Columbia, into orbit on April 12, 1981. Hurley and Behnken both two-time space shuttle fliers were among four astronauts chosen in 2015 for NASAs commercial crew program.

Elon Musk's SpaceX is the conductor and NASA the customer as businesses begin chauffeuring astronauts to the International Space Station. The drama unfolds from the exact spot where men flew to the moon and the last space shuttle soared from Kennedy Space Center. NASAs newest test pilots, Doug Hurley and Bob Behnken, are launching from home turf with SpaceX presiding over the countdown. Plagued with software problems, Boeings Starliner capsule is still a year from launching with Ferguson and two NASA astronauts. In terms of launch power, the relatively small Falcon 9 has far less than the space shuttle did, another layer of safety.