NASA scrubs Artemis SLS Moon rocket launch

Boffins wish this one engine would just chill out

NASA's Space Launch System remained rooted to the pad this morning at the Kennedy Space Center on the US East Coast after its launch was scrubbed by controllers.

The unmanned rocket was supposed to blast off around 0830 ET (1230 UTC). The flight would have been the first proper test of the multi-billion-dollar SLS – the US agency's two-stage super heavy-lifter rocket – which is designed to eventually take astronauts to the Moon by 2025 under the Artemis program.

Today's rocket, with an empty Orion crew capsule sitting atop the stack, was due to go fly around the Moon to evaluate its abilities and design ahead of any manned mission. However, that's been called off after one of the engines couldn't be set to the correct temperature.

Here's confirmation from NASA on the scrub:

It had already been somewhat of a fraught countdown as the loading of its cryogenic fuel was briefly postponed while managers eyed lightning storms lurking off the Florida coast.

After a delay of nearly an hour, fueling commenced and all initially seemed to go well. A chill-down of the main propulsion system and transfer lines went as expected. First, the liquid oxygen was transfered, and then the liquid hydrogen.

The sense of déjà vu was palpable as a hydrogen leak was detected; this also came up in earlier tests. A spike in the amount of hydrogen permitted to leak into a purge can was the issue.

Having taken engineering advice, managers pressed on. After a pause, the filling of the liquid hydrogen tank resumed first with a slow and then a fast fill. The concentration of leaking gas didn't increase outside of constraints, and yet another bullet appeared to have been dodged as the cryogenic tanks were filled and topped off.

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Even an apparent crack in an intertank flange – appearing as a line of frost – was explained by engineers as simply air being trapped and chilled in the flange's insulating foam, forming the ice that we could see. In other words, nothing to worry about.

However, it was one of the SLS's RS-25 engines that eventually halted NASA's first attempt to launch its Artemis Moon rocket. While three of the four engines were chilled correctly, by bleeding some of the cryogenic propellant to the engines, engine number three did not cooperate despite the best troubleshooting efforts of engineers, and could not get to the right temperature. Unfortunately, NASA had been unable to test this step during the previous wet dress rehearsal.

The countdown, which was already hanging by a thread, went into a hold at the T-40 minute mark before managers decided to throw in the towel and scrub this morning's launch.

NASA did not immediately confirm if the scrub would require a roll back to the Vehicle Assembly Building, or if the issue could be resolved at the pad. While the latter would keep the back-up launch dates of September 2 and 5 in play, a rollback would push back the launch date deeper into September or October.

The latest update from NASA reads:

The launch director halted today's Artemis I launch attempt at approximately 8:34 a.m. EDT. The Space Launch System rocket and Orion spacecraft remain in a safe and stable configuration. Launch controllers were continuing to evaluate why a bleed test to get the RS-25 engines on the bottom of the core stage to the proper temperature range for liftoff was not successful, and ran out of time in the two-hour launch window. Engineers are continuing to gather additional data.

Finally, we note that SpaceX was able to launch a Falcon 9 rocket on Saturday from Florida, carrying 54 Starlink broadband satellites to put into orbit. ®

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