Why has NASA delayed Artemis II Moon mission beyond March?

NASA is rolling away the Space Launch System (SLS) rocket off the launch pad since a March launch of the Artemis II mission is no longer plausible. The agency stated on Monday that the rocket's six-kilometre-long journey from the launch pad to the Vehicle Assembly Building (VAB) at the Kennedy Space Center, Florida, will begin on Tuesday.

"The quick work to begin preparations for rolling the rocket and spacecraft back to the VAB potentially preserves the April launch window, pending the outcome of data findings, repair efforts, and how the schedule comes to fruition in the coming days and weeks," NASA said in a statement.

The rollout was finalised after engineers were unable to troubleshoot a problem in the rocket's second stage following a successful completion of the second Wet Dress Rehearsal (WDR) of the rocket on Saturday. During the rehearsal, mission teams filled the launch vehicle with over 7,00,000 gallons of cryogenic propellant and simulated a full countdown similar to launch day to test the system readiness.

Why has NASA delayed Artemis II?

While the engineers fixed liquid hydrogen leaks during the WDRs, they were faced with a reduced helium flow into the Interim Cryogenic Propulsion Stage (ICPS) of the SLS rocket after the second rehearsal. The ICPS is the second stage which separates from the core stage in space and pushes the spacecraft attached to it further into deep space.

NASA uses helium bottles to purge the ICPS engines and pressurise the liquid oxygen and liquid hydrogen tanks. NASA administrator Jared Isaacman revealed on February 21 that the system worked correctly during the first and second WDR but engineers were unable to get helium flow through the vehicle later on.

According to Isaacman, this problem can only be solved after rolling back the rocket into the VAB. This, he said, 'will take the March launch window out of consideration.'

After the second WDR, NASA had confirmed that Artemis II will launch on March 6, but encountered the ICPS anomaly just hours later.

Artemis II will be the first crewed lunar mission since 1972.

NASA astronauts Reid Wiseman, Christina Koch, Victor Glover and Canadian Space Agency's Jeremy Hansen have been chosen for the mission that will last approximately 10 days. Artemis II is not a Moon landing mission as its primary objective is testing the Orion spacecraft and its life support systems with humans onboard.