Before there is any date to Artemis II to which any seriousness can be attached, over 700,000 gallons of cryogenic propellants will have flowed through Space Launch System ground hardware.
The Launch Pad 39B at the Kennedy Space Center is where NASA is conducting the Artemis II wet dress rehearsal to ensure the entire sequence of operations that transforms a stacked SLS and Orion into a launch-ready vessel: tanking, countdown operations and safe detanking. The test aims to simulate the conditions during the launch day without astronauts on board, which focuses on the interfaces between the rocket, the ground systems, and the people operating them.
The wet dress rehearsal begins with a procedural task that is difficult to carry out but easy to summarize: loading liquid hydrogen and liquid oxygen into SLS at controlled temperatures, pressures, and maintaining healthy conditions inside the vehicle. Even just that operation puts pressure on several systems simultaneously: commodity lines, sensors, software to run paths, pad support equipment, and controllers are monitoring off-nominal conditions that may impel holds or scrub-like test points. When the vehicle is completely filled, the exercise changes to a simulated countdown which deliberately incorporates scheduled pauses, the teams can be trained to stop and restart the sequence when time constraints are in effect. This is where the role of choreography comes in: it is not merely a clock, but a set of checks and transfers, which should be functioning in the same manner each and every time. In the case of Artemis II, managers too desire to be sure that problems observed throughout the 2022 campaign are not lying in ambush to recur when the vehicle is fully loaded and cold. The outcome is a rehearsal that considers the ground system flight hardware in its own right.
In contrast to a crewed countdown, it does not have the most visible members of the mission. Astronaut Reid Wiseman, Victor Glover, Christina Koch, and the Canadian Space Agency astronaut Jeremy Hansen went into the standard health stabilization program, a period of about 14 days of quarantine that is meant to minimize the chance of an illness revising the image of the launch towards its end.
To the general population, the story of the quarantine is like a footnote. Another dependency, operationally, is that it guards the mission schedule, but can be put on hold and reinstated at any time to keep the flexibility maintained as pad testing is performed.
The newest pad work has involved maintenance of the solid rocket boosters, where hydrazine is filled into the booster aft skirts, and closeouts were still being performed on the inside of Orion. Smaller-but-revealing readiness items have also been monitored by ground teams. Pad emergency escape inspection revealed that the slide-wire baskets of transporting occupants off the mobile launcher were not as far traveling than anticipated; changes in brakes were implemented so that the system will reach its full descent. Individually, technicians anticipated further sampling of Orion potable water following initial findings of larger total organic carbon than anticipated, a case of how information about crews flight details is not limited to propulsion and structures.
The Florida weather is not left out of the engineering narrative since a fully stacked car is parked on the pad. At the reduced-than-normal temperatures, which will be experienced during the flow, teams have been developing environmental control mechanisms, which maintain Orion and parts of SLS that are not covered by the cover to be within acceptable limits.
Wet dress rehearsal results provided to mission managers act as a gateway that determines whether the vehicle will be allowed to proceed to a launch attempt or it will go back to the Vehicle Assembly Building to undergo more work. In the case of Artemis II, that ruling also bridges the gap to a mission that is not a landing, but a full-up crewed test of SLS, Orion and the sort of operational discipline one needs in order to go on a lunar flyby that lasts some 10 days.