NASA has a problem. It has a big rocket under development. It has a shiny new spacecraft to fly into deep space. And it has a cadre of brilliant astronauts waiting in a long line to fly beyond low-Earth orbit. But the SLS rocket, Orion spacecraft and crew members have nowhere to go—there is no Moon lander, and asteroids and Mars are too far away for now.
NASA plans to address its problem by parking a “deep space” habitat in a location near the Moon, which astronauts could visit and use to become acclimated to life beyond low-Earth orbit. President Obama mentioned deep space habitats earlier this month, when he reiterated his call for NASA to send humans to Mars. “I'm excited to announce that we are working with our commercial partners to build new habitats that can sustain and transport astronauts on long-duration missions in deep space,” Obama said.
from Six contractors have begun work on NASA’s gateway to deep space