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NASA will attempt another 'hot fire' test of its SLS moon rocket today. Watch it live!

Update for 5:29 pm ET: NASA has successfully test fire the Space Launch System core booster for the Artemis 1 mission to the moon. You can see a replay above. The SLS megarocket's four main engines fired for just over 8 minutes. Our full wrap story will be posted shortly.

Preview story: 

NASA is ready to make another attempt to certify its moon megarocket for spaceflight.

The agency plans to do a test of its Space Launch System (SLS) rocket core stage at NASA's Stennis Space Center near Bay St. Louis, Mississippi, on Thursday (March 18), during a two-hour window that opens at 3 p.m. EDT (1900 GMT or 2 p.m. local time at Stennis).

Live coverage of the test should start on NASA Television roughly half an hour before the hot fire test, although the agency says it will "refine the timeline as it proceeds through operations." The latest timing information will be available on NASA's Twitter feed on test day. You can watch the webcast live in the window above, courtesy of NASA, or directly via NASA TV.

Video: How NASA's SLS megarocket engine test works

"Engineers will power up all the core stage systems, load more than 700,000 gallons of cryogenic — or supercold — propellant into the tanks, and fire the rocket's four RS-25 engines at the same time to simulate the stage's operation during launch, generating 1.6 million pounds of thrust," NASA said in a description of the testing procedure.

This is NASA's second attempt at doing a hot fire test of SLS, after the first test shut down unexpectedly early in January. The agency is close to getting this SLS rocket ready to fly the Artemis 1 round-the-moon uncrewed mission, but the "Green Run" series of tests have encountered several delays and technical problems in recent months.

The core stage for the SLS rocket is pictured on the B-2 Test Stand at NASA's Stennis Space Center near Bay St. Louis, Mississippi, during a hot fire test on Jan. 16, 2021.  (Image credit: NASA)

Artemis 1, so far, is supposed to fly to the moon at the end of 2021 to get the agency ready for crewed missions. But making the flight date will depend on SLS passing these tests and getting shipped to its launch site in Florida in time. The young Joe Biden administration hasn't committed to a timeline yet to put people on the moon, but previous to that, NASA was planning an Artemis 3 landing in 2024.

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Elizabeth Howell

Elizabeth Howell is a contributing writer for Space.com who is one of the few Canadian journalists to report regularly on space exploration. She is the author or co-author of several books on space exploration. Elizabeth holds a Ph.D. from the University of North Dakota in Space Studies, and an M.Sc. from the same department. She also holds a bachelor of journalism degree from Carleton University in Canada, where she began her space-writing career in 2004. Besides writing, Elizabeth teaches communications at the university and community college level, and for government training schools. To see her latest projects, follow Elizabeth on Twitter at @howellspace.