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  At 4:27pm central time, the SLS rocket core stage ignited its four RS-25 engines at NASA’s Stennis Space Center. The test was to last up to eight minutes. [credit:
  Trevor Mahlmann for Ars ]

STENNIS SPACE CENTER, Miss.—For a few moments, it seemed like the Space Launch System saga might have a happy ending. Beneath brilliant blue skies late on Saturday afternoon, NASA’s huge rocket roared to life for the very first time. As its four engines lit, and thrummed, thunder rumbled across these Mississippi lowlands. A giant, beautiful plume of white exhaust billowed away from the test stand.

It was all pretty damn glorious until it stopped suddenly.

About 50 seconds into what was supposed to be an 8-minute test firing, the flight control center called out, “We did get an MCF on Engine 4.” This means there was a “major component failure” with the fourth engine on the vehicle. After a total of about 67 seconds, the hot fire test ended.