NASA Completes ‘Wet Dress Rehearsal’ of Its Most Powerful Rocket

NASA Completes ‘Wet Dress Rehearsal’ of Its Most Powerful Rocket
The core stage of NASA's Space Launch System (SLS) in the B-2 Test Stand at NASA's Stennis Space Centre near Bay St. Louis, Mississippi. (Image: NASA)
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Engineers from NASA and Boeing have added cryogenic propellants to the core stage of the Space Launch System (SLS), reaching a major milestone in the development of this advanced rocket.

That’s seven down, one to go.

NASA is in the midst of its SLS core stage Green Run testing, a series of tests to ready the rocket for a long-anticipated actual launch. The latest test, conducted on Sunday at NASA’s Stennis Space Centre in Mississippi, was dubbed the “wet dress rehearsal,” in which engineers loaded more than 2,649,787 l of cryogenic propellants into the rocket’s tanks. The propellant was then controlled and drained, “returning the stage to a safe condition,” according to a NASA statement.

NASA can now check the seventh item off this list.  (Graphic: NASA) NASA can now check the seventh item off this list. (Graphic: NASA)

With this seventh Green Run test complete, NASA can now look ahead to the eighth and final test, in which all four RS-25 engines will be fired for upwards of eight minutes. This test will set the stage for certification and the dawn of the Artemis era. NASA is hoping to launch SLS, sans crew, in November 2021.

The 64.62 m-tall SLS rocket, with its massive four-engine core stage, is an integral component of the Artemis program. The current plan to send astronauts to the lunar surface in 2024 could be disrupted if the SLS program fails to deliver on time.

Propellant for SLS consists of liquid hydrogen and liquid oxygen. Together, this propellant serves as fuel and as the oxidising agent needed to make the fuel burn. The chemicals are cooled to ultra-low temperatures to keep the propellant in a compact liquid form. Six barges delivered the required propellant for the test, a feat made possible thanks to a network of waterways in the region. The fuelling was done as the SLS core rocket section was steadied by the facility’s B-2 test stand.

NASA and Boeing engineers carefully monitored all core stage systems during the test. A preliminary look at the data suggests the “stage performed well during the propellant loading and replenish process,” according to NASA.

But the test wasn’t perfect. The plan was to simulate an actual countdown with propellant in the core, but the test abruptly ended when the clock reached T-33 seconds, for reasons that aren’t yet known. The “core stage and the B-2 test stand are in excellent condition, and it does not appear to be an issue with the hardware,” explained NASA, adding that the “team is evaluating data to pinpoint the exact cause of the early shutdown.”

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This apparent not-a-problem notwithstanding, NASA will now move ahead with the eighth Green Run test, which should be far more exciting than the loading of propellants. Indeed, we’re itching to see this monster get all fired up, even if it has to remain on the ground. At least for now.