WASHINGTON — Tests of the space shuttle-derived RS-25 engine, an Aerojet Rocketdyne product being adapted for the main stage of NASA’s Space Launch System after powering 135 space shuttle flights, resumed at NASA’s Stennis Space Center in Mississippi May 28.

Like all RS-25 hot-fires, the latest took place on Stennis’ A-1 test stand, which was built to test the second stage of the Apollo program’s Saturn 5 moon rocket.

The May 28 hot-fire test lasted 450 seconds and marked the end of a four-month gap in the RS-25 testing program, which was halted after a Jan. 9 hot-fire. NASA, in its official post about the latest test, said the delay was to accommodate scheduled maintenance. The agency made no mention of defects in the A-1 stand’s new fuel lines, which the Government Accountability Office (on page 59 of this year’s annual report on big NASA projects) identified as a leading cause of the pause in the hot-fire program.

NASA’s video, above, of the May 28 test pairs nicely with its coverage of Jan. 9 hot-fire, if for no other reason than the winter test took place at night.

Have a look:

Last but not least, here’s a time-lapse video, courtesy of Aerojet Rocketdyne, of contractors at Stennis assembling an RS-25. The video crams about three months of work (completed in April) into two minutes, Aerojet Rocketdyne spokeswoman Mary Engola said.

The engine in the video (which never powered a shuttle mission) will power the second of two budgeted SLS flights, which is set to liftoff around 2021 and carry a pair of astronauts to a distant lunar retrograde orbit in what would be the first crewed mission to lunar space since Apollo 17 in 1972.

There’s some interesting stuff in the comments section for this video. Be sure to click through, after you watch.

Dan Leone is a SpaceNews staff writer, covering NASA, NOAA and a growing number of entrepreneurial space companies. He earned a bachelor’s degree in public communications from the American University in Washington.