The so-called "gateway spacecraft" would hover in orbit on the far side of the moon, support a small astronaut crew and function as a staging area for future missions to the moon and Mars.
At 277,000 miles from Earth, the outpost would be far more remote than the current space station, which orbits a little more than 200 miles above Earth. The distance raises complex questions of how to protect astronauts from the radiation of deep space — and rescue them if something goes wrong.
NASA Chief Charlie Bolden briefed the White House earlier this month on details of the proposal, but it's unclear whether it has the administration's support. Of critical importance is the price tag, which would certainly run into the billions of dollars."