The last time the folks at NASA tested a crewed lunar lander in low-Earth orbit, here’s how they did it. First, a Saturn 5 rocket lifted off from the Kennedy Space Center (KSC) in Florida carrying three astronauts, an Apollo spacecraft, and a lunar module. Then they got to orbit and the astronauts flew both ships. Then they came home. That straightforward mission was accomplished 57 years ago, during the flight of Apollo 9.

The next time NASA attempts something of the kind—during the planned flight of Artemis III in the summer of 2027—things will be a lot more complicated. First an uncrewed Blue Origin New Glenn rocket will launch from KSC carrying the company’s Blue Moon lander into orbit. Then NASA will launch its prosaically named Space Launch System (SLS) moon rocket, carrying the four Artemis III astronauts aboard an Orion spacecraft. Then the crew will rendezvous with the Blue Moon, dock with it and enter it, checking out its systems before returning to the Orion.…