NASA's first Space Launch System megarocket core powers up for 'green run' test

sls rocket core stage
The core stage of the first SLS rocket on the test stand at NASA's Stennis Space Center in Mississippi. (Image credit: NASA)

The coronavirus pandemic has slowed testing of NASA's next megarocket, but the monthslong process is resuming and has checked off a key milestone: powering up the core stage.

The Space Launch System, or SLS, will be the most powerful rocket to date when it first launches, and its debut flight is currently scheduled for next year. Boeing, the company NASA contracted to lead the rocket's construction, is now testing the core stage of the first SLS at the agency's Stennis Space Center in Mississippi. The qualification procedure is an eight-stage process dubbed the "green run" test and began in January.

"It's very rewarding," Mark Nappi, Boeing's green-run director, told "It's the first time that this test has been run; this is a first-of-its-kind type of rocket, the world's largest, most powerful rocket ever built."

Related: Watch NASA crush a SLS megarocket tank until it explodes (video)

The green-run tests will culminate with a hot-fire test, during which the rocket will be tied down but will otherwise endure each step as if a launch were taking place. Currently, the Boeing crew expects the hot-fire test to happen in October, Nappi said.

The process has been slowed considerably by the coronavirus pandemic that has swept the country this year. The team completed just one test before the pandemic struck the region in earnest in March and agency leadership halted on-site work at Stennis.

The center began reopening slowly in mid-May, and the green run team completed their second test on the core stage in late June. That test powered up the core stage to ensure that the software and other electrical interfaces involved in the rocket and the testing stand work properly.

Next, the testing personnel will verify that they can stay in control of the rocket during later tests even if critical communications systems were to fail — a procedure currently scheduled to take place on Monday (July 6), Nappi said. "It's an important precursor to going into the hot fire, knowing that we have redundant paths to being able to turn the vehicle off," John Cipoletti, Nappi's deputy on green-run testing, told

The next two tests will check the core stage's valves, hydraulics and the like to ensure the vehicle is ready for more active tests. Then the green-run team will take a step back from the rocket and instead run a drill on themselves, going through the motions of the final tests.

Those last two tests are a "wet dress rehearsal" that sees the rocket stage loaded with fuel and the full hot-fire test to ensure the vehicle is truly ready for launch. Successful wet-dress and hot-fire tests are crucial for engineers to feel confident the vehicle is safe.

It's an intense procedure but not one that all future SLS core stages will need to endure. The equipment enduring the tests will be inspected after a successful hot fire, refurbished as needed, and then shipped to NASA's Kennedy Space Center in Florida, where still more tests await the core stage. But eventually, if all goes well, the SLS core will take flight next year and visit the moon, in the first uncrewed mission of NASA's Artemis program that is designed to land humans on the moon in 2024.

"It is truly a huge, a huge rocket and very impressive in its capability and its size," Cipoletti said. "To be a part of setting something up that's in the future going to get people to Mars is just a wonderful experience."

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Meghan Bartels
Senior Writer

Meghan is a senior writer at and has more than five years' experience as a science journalist based in New York City. She joined in July 2018, with previous writing published in outlets including Newsweek and Audubon. Meghan earned an MA in science journalism from New York University and a BA in classics from Georgetown University, and in her free time she enjoys reading and visiting museums. Follow her on Twitter at @meghanbartels.