NASA is gearing up for the final crucial test of its Space Launch System (SLS) rocket, the giant booster designed to return humans to the moon by 2024 and expected to fly its first mission, dubbed Artemis 1, in late 2021.
Artemis 1 will be an uncrewed mission to launch the Orion spacecraft atop an SLS rocket to the moon to prove that the system is capable of flying humans in the near future. The SLS rocket has approximately the same diameter (30 feet) as SpaceX’s deep space booster, Starship, but is about 40 percent shorter. (SLS is 212 feet tall. The latest Starship prototype is 400 feet tall.)
NASA has been testing various technologies related to the Artemis program in a test series called Green Run since the project’s inception in 2017. The space agency is expected to complete the eighth, and final, part of the test series, a hot fire test of the SLS booster, as soon as January 17 at its Stennis Space Center near Bay St. Louis, Mississippi.
NASA conducted the seventh part of the Green Run test series last month at the Mississippi site. It was a wet dress rehearsal where the SLS booster’s two giant fuel tanks were loaded with (and later drained of) 733,000 gallons of cryogenic propellant (liquid hydrogen and liquid oxygen) for the first time. The delivery alone took 114 fully loaded tanker trucks.
The only hiccup during the wet dress rehearsal is that the test was automatically cut off a few minutes early due to a timing error on a valve closure. Subsequent analysis revealed that the valve’s predicted closure was off by a fraction of a second. The SLS team later corrected the issue, and the rocket is now ready for the final hot fire test.
“During our wet dress rehearsal Green Run test, the core stage, the stage controller, and the Green Run software all performed flawlessly, and there were no leaks when the tanks were fully loaded and replenished for approximately two hours,” Julie Bassler, SLS Stages manager at NASA’s Marshall Space Flight Center in Huntsville, Alabama, said in a statement this week. “Data from all the tests to date has given us the confidence to proceed with the hot fire.”
The upcoming hot fire test will fire all four of SLS’ RS-25 engines simultaneously for up to eight minutes to simulate the core stage’s performance during launch.
Last September, a shorter hot fire test was performed at a Northrop Grumman facility in the Utah desert. A full-size SLS booster fired up for two minutes while laid horizontally at the test site. The exhaust generated by the engine was so hot that it instantly turned the sand nearby into glass.
NASA has a packed schedule in 2021. On December 31, the agency published a short video (embedded below) hyping its plans for the new year, highlighting the Artemis program as the central theme of the preview.