This liquid fuel engine is a beast.

Flight controllers could be heard during the test referring to an “MCF” (a major component failure) apparently related to engine No. 4 on the SLS booster. John Honeycutt, NASA’s SLS program manager, added that at about the 60-second mark, cameras caught a flash in a protective thermal blanket on the engine, though its cause and significance remain to be determined.

Honeycutt said it’s too early to know if a second hot-fire test will be required at Stennis, or if it can be done later at NASA’s Kennedy Space Center in Florida, where the SLS is scheduled to launch the uncrewed Artemis 1 mission around the moon by the end of this year. Similarly, it’s too early to know if Artemis 1 will still be able to launch this year.

“I think it’s still too early to tell,” Bridenstine said of whether a 2021 launch for Artemis 1 is still in the cards. “As we figure out what went wrong, we’re going to know kind of what the future holds.”

During a press conference on Tuesday (Jan. 12), John Shannon vice president and program manager for SLS at Boeing, said that the engines needed to run for a certain amount of time to get the data they needed. “If we had an early shutdown, for whatever reason, we get all of the engineering data we need to have high confidence in the vehicle at about 250 seconds,” Shannon said.

Since the test was stopped short of 250 seconds, and before the teams were able to gimble (or move) the engines, exactly how much data and how confident the teams are in the vehicle is yet to be determined.

Saturday’s test was initially moved up an hour to 4 p.m. EST (1900 GMT) as test preparations were ahead of schedule. However, during the countdown, engineers put the count on hold to work through water deflection system checks and other tests on the engine test stand. The teams were able to work through the issues and resume the count in time to complete the test Saturday, despite the short run time.

The exercise, known as a hot-fire test, put the core Space Launch System booster components — the four RS-25 main engines, fuel tanks and the rockets computers and avionics — through their paces. The test simulated a launch while holding the rocket firmly in place, affixed to a test stand. (The same test stand was used to test out the engines on both NASA’s Saturn V rocket and space shuttle orbiters.)

“The SLS rocket is the most powerful rocket ever built in the history of humanity,” Bridenstine said on NASA TV shortly before the test. “This is the same rocket that, by the end of this year, will be launching an Orion crew capsule around the moon.”