The engine used for today's firing was RS-25 development engine 0528, a ground test unit that had not seen action since the space shuttle program. Since January 2015, the Space Launch System program has completed eight hot-fire tests on Stennis' A-1 test stand. Today's partial test was the ninth.

The first seven tests were conducted with development engine 0525, and the series wrapped up in August 2015. The eighth test, which took place in March 2016, used engine number 2059, a veteran shuttle engine that is slated for use on the second flight of SLS between 2021 and 2023.

Today's hot-fire was the first of a five-test series with development engine 0528. A second firing is tentatively scheduled for August 16, though it remains unclear how today's glitch will affect long-term schedules. The last three tests will be conducted with the flight engine controller that will be used on the Space Launch System's maiden launch, Exploration Mission 1, in 2018. Those tests are expected in November through December.