STENNIS SPACE CENTER, Miss. - NASA conducted its fourth RS-25 single-engine hot fire of the year May 20, a continuation of its seven-part test series to support development and production of engines for the agency’s Space Launch System (SLS) rocket on future missions to the Moon. The engine was fired for more than 8 minutes on the A-1 Test Stand, the same amount of time RS-25 engines need to fire for launch of the SLS rocket. The test series is designed to provide data to Aerojet Rocketdyne, prime contractor for the SLS engines, as it begins production of new engines for use after the first four SLS flights. (Source: NASA/SSC, 05/20/21)