NASA rules out March Artemis II launch after helium flow interruption, readies rollback

Engineers discovered an interruption in helium flow to the Space Launch System upper stage overnight between Feb. 20 and Feb. 21, prompting NASA to announce Feb. 21–22 that the agency will not meet an earlier early-March target for Artemis II and is preparing to roll the SLS rocket and Orion spacecraft back from Launch Complex 39B to the Vehicle Assembly Building at Kennedy Space Center for troubleshooting and repairs.

Helium on the vehicle maintains engine environmental conditions and pressurizes the liquid hydrogen and liquid oxygen propellant tanks on the stage, sometimes called the interim cryogenic propulsion stage. The problem was identified in post-test data after a second wet dress rehearsal; helium had functioned during the rehearsals but teams were "not able to properly flow helium during normal operations" afterward, NASA said.

The decision removes the five potential March launch opportunities NASA had been targeting - counted as March 6 through 9 and March 11 - and forces the program to pivot to a set of April windows that officials say they may still preserve if a rollback and repairs proceed quickly. The April opportunities cited by NASA planning teams include April 1, April 3 through 6 and April 30, a total of six possible days if schedule and data permit.

Agency officials emphasized safety and data-driven caution. John Honeycutt, chair of NASA's Artemis 2 mission management team, said in pre-existing remarks about vehicle readiness, "I've got a pretty high level of confidence in the configuration that we're in right now. It's out there at the pad. It's going to be there at the pad until we go fly." Joshua data review and engineering work will determine whether that confidence holds after rollback testing.

Jared Isaacman posted on X after the overnight data review that teams were troubleshooting and preparing for a likely rollback to the VAB. "This will almost assuredly impact the March launch window," he wrote, acknowledging the setback and the prospect of delay. NASA's blog stated in formal language that "A rollback would mean NASA will not launch Artemis II in the March launch window. However, the quick preparations enable NASA to potentially preserve the April launch window if a rollback is required, pending the outcome of data findings, repair efforts, and how the schedule comes to fruition in the coming days and weeks."

Operators are already maintaining the rocket in a safe state while they prepare for movement. "Operators are using a backup method to maintain the environmental conditions for the upper stage engines and the rocket, which remains in a safe configuration," agency officials said, underscoring that no active catastrophic failure was reported and that immediate crew safety concerns do not apply because the vehicle remains uncrewed on the pad.

Artemis II is slated to be the first crewed lunar flyby since Apollo 17, carrying three NASA astronauts and one Canadian on a roughly 10-day mission to loop around the Moon and return. The program has faced a string of prelaunch issues this year, including a January winter-storm disruption, an earlier liquid hydrogen leak during a simulated countdown, and extended closeout work after prior dress rehearsals.

If NASA proceeds with a rollback, technicians will rework the helium feed and related systems inside the VAB, compare telemetry with the uncrewed Artemis I upper-stage helium troubleshooting from 2022, and then set a revised launch date range. The agency has not announced a firm rollback timeline; teams said they will brief Congress and the public as findings and schedule updates become available.

Photographs of the rocket at LC-39B were taken by Gregg Newton/AFP via Getty Images.