NASA SLS Rocket Test Canceled At The Last Minute Over Safety Risk

NASA was scheduled to conduct a key test of its Space Launch System rocket and spacecraft today but had to scrub the event part way through due to an issue with its mobile launcher platform. The agency announced the last-minute change of plans on Twitter, explaining that it will proceed with the test in the future — possibly as early as Monday, April 4, though that's yet to be seen.

The day started with test authorization from the agency's launch director, NASA said in a blog post. Initial steps were taken to prepare for the test, including the final actions required to connect the mobile launcher with the SLS rocket and its Orion companion. Though the weather remained favorable, NASA said in a subsequent update on its Artemis website that it had to cancel this particular test due to problems with pressurizing the mobile launcher. Put simply, an issue arose that made it too risky for the team to load the rocket with propellants, something that'll hopefully be fixed in the near future.

This key rocket test is called the Artemis I Wet Dress Rehearsal by NASA, which said this particular event is intended for its team to rehearse the inevitable future countdown milestones that'll take place when the first actual launch happens. As such, the rocket's engines weren't set to be lit, but various processes were initiated, including everything from closing the system's umbilicals to moving the flame deflectors and — the part that ultimately caused the stumble — loading liquid hydrogen and oxygen into the rocket's cryogenic propulsion stage tanks and the core stage.

In its most recent update on the matter, NASA said its technicians weren't able to properly pressurize the mobile launcher destined for connection with the SLS. This was a problem because positive pressure is used, in part, to keep the dangerous propellant gases from building up within the mobile launcher's sealed spaces.

The lack of proper pressurization meant the technicians couldn't complete the part of the rehearsal that involved loading the propellants — at least not without putting themselves at risk of harm, which is why the process was stopped. Rather than proceed today, NASA says its experts will figure out how to proceed with the wet dress rehearsal in the near future, something, the space agency notes, may happen as soon as tomorrow. The next wet dress rehearsal will depend partly on when the fuel is available again.