NASA prepares for likely rollback of SLS, delaying Artemis II to April

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NASA is gearing up for a likely rollback of the Space Launch System (SLS) rocket and Orion spacecraft to the Vehicle Assembly Building (VAB) at Kennedy Space Center in Florida.

The decision follows an unexpected interruption in helium flow within the rocket’s interim cryogenic propulsion stage (ICPS), observed overnight on Saturday, February 21, 2026.

This issue with the ICPS has prompted teams to review data and prepare contingency measures, effectively ruling out the targeted March launch window and pushing the mission toward a possible April liftoff if the rollback is confirmed.

Pre-rollback work is already underway, including the removal of pad access platforms installed yesterday. These platforms are subject to wind constraints and cannot be removed during high winds, which are forecasted for tomorrow.

Following a successful second Wet Dress Rehearsal (WDR), NASA took the unusual step of announcing a target launch date of March 6 for Artemis II—despite traditionally waiting until the completion of the Flight Readiness Review (FRR) to set firm dates.

Less than 24 hours later, that date became non-viable after an overnight helium flow anomaly was noted.

NASA Administrator Jared Isaacman addressed the development in a statement, emphasizing the troubleshooting efforts underway.

“After overnight data showed an interruption in helium flow in the SLS interim cryogenic propulsion stage, teams are troubleshooting and preparing for a likely rollback of Artemis II to the VAB,” Isaacman said. “This will almost assuredly impact the March launch window.”

Notably, NSF was hearing rumors of a potential vehicle issue that could result in a rollback on Saturday morning. Less than an hour later, NASA and Isaacman published a statement online—an impressive sign of the Administrator’s commitment to increasing transparency at the agency.

The ICPS, or Interim Cryogenic Propulsion Stage, is effectively the SLS rocket’s upper stage.

Derived from the Delta IV rocket’s second stage and adapted for Artemis missions, it uses liquid hydrogen (LH2) and liquid oxygen (LOX) as propellants to provide the necessary thrust after core stage burnout, enabling the Orion spacecraft to reach lunar orbit insertion trajectories.
Helium plays a vital role in this system. Stored in onboard bottles, it purges the engines of residual gases and pressurizes the LH2 and LOX tanks during ascent.

According to Isaacman, the ICPS helium system performed flawlessly during the first two Wet Dress Rehearsals (WDRs), which are full-scale fueling simulations conducted at Launch Pad 39B. The second WDR, in particular, proceeded according to plan with no indications of helium issues.

“The ICPS helium bottles are used to purge the engines, as well as for LH2 and LOX tank pressurization. The systems did work correctly during WDR1 and WDR2,” he noted.

The problem emerged during a routine repressurization operation last evening, catching teams off guard.

“This was an unexpected development during routine helium flow operations last evening. The teams were up all night assessing the situation,” Isaacman added.

Engineers are investigating potential causes, drawing parallels to a similar failure signature encountered during the Artemis I uncrewed mission in 2022.

Possible faults include a final filter on the umbilical connection between ground systems and the vehicle, a failed quick-disconnect (QD) umbilical interface—where issues have been noted before—or a malfunctioning check valve onboard the rocket.

Corrective measures were implemented post-Artemis I to reduce such risks for Artemis II, but the recurrence underscores the challenges of cryogenic systems in extreme environments.

Isaacman also explained why a rollback is likely: remediation for any of these issues requires access only available in the VAB, which features numerous platform levels that rotate into place around the stack.
“Regardless of the potential fault, accessing and remediating any of these issues can only be performed in the VAB,” he confirmed.

The vehicle remains in a safe configuration, relying on ground-based environmental control systems (ECS) for engine purging instead of the onboard helium supply.

This potential rollback echoes delays in previous Artemis preparations, where weather, technical glitches, and supply chain issues have repeatedly extended timelines. The March window, already tight, now appears off the table, with April emerging as the next viable opportunity—assuming swift resolution.

“A rollback would mean NASA will not launch Artemis II in the March launch window,” NASA noted. “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.”

NASA is set to provide another update during the coming week, which will also address requirements for a rollback, including resolution and return to the pad.

The latter may require at least a tanking test or mini-WDR to confirm that the trip up and down the crawlerway did not affect systems such as the LH2 tail service mast umbilical (TSMU), which necessitated WDR2.

Lead photo: Tyler Gray for NSF.

The post NASA prepares for likely rollback of SLS, delaying Artemis II to April appeared first on NASASpaceFlight.com.



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