The Artemis II stack was on Pad 39B following a complete up fueling exercise which had pumped 700,000 gallons of cryogenic propellants through the Space Launch System and then pumped them out again without incident. In hours, engineers discovered the next limiting factor: a continuous supply of helium to the interim cryogenic propulsion stage of the rocket.
Helium is not a source of thrust, but lack of it can bring down a lunar mission. Helium is used on the SLS upper stage to ensure that the correctly required conditions in the engine are maintained, as well as pressure the liquid oxygen and liquid hydrogen tanks. The system worked as anticipated in wet dress rehearsal operations, but was not capable of circulating helium properly in routine reconfigurations afterwards, a difference that indicates the interface between ground systems and flight hardware and not a one dramatic failure. NASA put the vehicle in a safe state and operators kept the conditions under a backup mechanism, and purchased time to conduct analysis without jeopardizing the stack on the pad.
Its practical implication is straightforward: schedule is driven by access. NASA started to prepare to roll the rocket and Orion spacecraft back to the Vehicle Assembly Building since the most accessible fix areas, ground-to-vehicle lines, a valve on the stage or instalment between ground and rocket, are not readily accessable at the pad. The rollback itself is a sluggish and methodical process: a day long relocation across approximately four miles that replaces the openness of Pad 39B with the regulated and multi-storied performer platforms within the VAB. The opportunity to launch in April will also be safeguarded by that decision since it will provide the opportunity to do hands-on troubleshooting faster once the stack is inside. “This will almost assuredly impact the March launch window,” NASA Administrator Jared Isaacman wrote.
The helium anomaly is also a reminder of an existing reality, which is that performance on the scripted test is not a guarantee of margin during the less-observable transitions that follow. NASA update reports that NASA engineers are considering a list of faults candidates, which include a valve in the upper stage and a filter between the ground and rocket, plus the ground/rocket interface where helium is directed. During Artemis I, teams also made comparisons of the signature to helium related troubleshooting as an engineering constraint and not footnote of flight history. This method, data review, targeted access, retest, is a manifestation of a program that is developed as a test campaign, with each closed-loop investigation making both the processes and the hardware more robust to the following crewed step.
Artemis II is the initial program crewed mission: a 10-day mission with NASA astronauts Reid Wiseman, Victor Glover, and Christina Koch aboard with Canadian astronaut Jeremy Hansen aboard, orbiting the moon without landing. Orion will launch humans at about 4,600 miles above the moon, with greater emphasis on life support, navigation, communications, and the integrated SLS-Orion stack in the deep space. Despite the successful validation of the uncrewed Artemis I, it is not until Artemis II that these systems are working as a single, human-rated chain-cryogenic loading, all the way up to spacecraft operations at significant distance.
The human element of the schedule adjusts as the helium issue is handled by ground teams. Artemis II crew went into quarantine again to fuel the test and out of quarantine when the launch target shifted away leaving them in a position that keeps them on their toes but does not subject them to spurious isolation. Simultaneously, engineering teams are working on the limited scope: fix reliable helium flowing using regular operations, verify the fix using the right ground tests, and maintain the next window without requesting the rocket to fly under less than verified performance conditions.
