Gateway or bust: NASA's plan for a 2024 lunar landing depends on a much-criticized orbital outpost

WHEN ASTRONAUTS FIRST landed on the moon a half century ago, they went there in a single shot: A Saturn V rocket launched the Apollo command and service module and the lunar lander, which entered into a low orbit around the moon. The lander then detached and descended to the surface. After 22 hours in the moondust, the Apollo 11 astronauts climbed into the lander's ascent stage and returned to the command module for the trip back to Earth. NASA's current plan for sending astronauts back to the moon, which may happen as soon as 2024, goes a little differently. A series of commercial rockets will first launch the components of a small space station, which will self-assemble in high lunar orbit. Then another rocket will send up an unoccupied lunar lander. Finally, a giant Space Launch System (SLS) rocket will launch an Orion spacecraft (which looks a lot like an Apollo command module), with astronauts inside. Orion will dock with the space station, and some of the astronauts will transfer to the waiting lander. Finally, the astronauts will descend to the lunar surface. After their sortie on the moon, they'll return to the orbital station, where the crew will board Orion for the trip home. That lunar orbital space station is envisioned as a collection of modules, including habitats, an air lock, and a power and propulsion unit. NASA calls it the Gateway.