An Aerojet Rocketdyne RS-25 rocket engine was tested on the A-1 Test Stand at the John C. Stennis Space Center in Mississippi, on 28 January 2021, at 22:53 UTC (16:53 CDT, 17:53 EDT). The test was conducted using the RS-25 developmental engine No. 0528 and had a duration of 500 seconds (full-duration test). This RS-25 hot-fire test is part of the Retrofit-2 test series, aiming to evaluate new engine components and reduce risk in engine operation. NASA’s Space Launch System (SLS) will be powered by four RS-2