Slowed by four main parachutes in predawn darkness, the SpaceX Dragon Endeavour spacecraft descended and splashed down in the Pacific Ocean on Thursday, Jan. 15, wrapping up NASA's first-ever astronaut medical evacuation from the International Space Station.

With Artemis II, SLS could become the most powerful rocket ever to launch humans. Its four main engines burn roughly 700,000 gallons of ultra-cold fuel, producing enough oomph to keep eight Boeing 747s aloft. Future versions of SLS, if they come to fruition, could deliver even greater power.