Annis and the other two members of the crew, Billy Cairns and Chad Garrett, were sent to the mobile launch platform at the base of SLS to tighten down "packing nuts," hardware that helps form a tight seal on the replenishment valves through which liquid hydrogen was pumped into the Artemis 1 moon rocket's core stage after the main tanking procedure. Because hydrogen is such a small molecule, it manages to find its way out of even the tightest seals, meaning NASA has to keep replenishing the hydrogen fuel tanks throughout the launch countdown even after main fueling procedures have...