First Engine Installed on SLS as NASA Orders More Rockets, Conducts Pathfinder Ops in Florida

Engineers at NASA’s Michoud Assembly Facility in New Orleans have structurally mated the first of four RS-25 engines to the core stage for NASA’s Space Launch System (SLS) rocket that will help power the first Artemis mission to the Moon. Photo Credit: NASA/Jude Guidry

NASA is full steam ahead with the Space Launch System, as years of development and manufacturing continue transitioning into flight hardware final assembly and integration for the upcoming Artemis moon missions after the turn of the decade.

The agency just ordered a third rocket core and is finalizing details with Boeing for a contract of up to 10, while workers at the launch site in Florida practice processing ops with a recently arrived pathfinder, and technicians at Michoud Assembly Facility in New Orleans install the four flight engines on the bottom of the enormous 212-foot tall core stage for the first SLS flight – Artemis 1.

RS-25 Engine Hot Fire Test on the A-1 test stand at Stennis. Photo: Aerojet Rocketdyne

Known as the Ferrari of rocket engines, the Aerojet Rocketdyne RS-25s which once helped power the space shuttles off world have been modified to produce more power, each featuring a new controller, or ‘brain’, to help control engine operation and facilitate communication between the engines and rocket. Guzzling 733,000 gallons of liquid oxygen and liquid hydrogen, the four engines will produce more than 2 million pounds of thrust on launch.

Over the last 4 years, all 16 of the engines have been modified from their reusable shuttle-era configurations, tested, and cleared for flight on the first four SLS Artemis missions.

Image via NASA

NASA and Boeing finished assembling and joining the main structural components of the first core stage last month, and with the first engine now mated to the rocket technicians will now integrate the propulsion and electrical systems, then repeat for each of the other three engines and completing final assembly of the Artemis I core stage in December.

At the same time, technicians will also be building, outfitting and assembling the core stage for Artemis II, the first mission that will send astronauts to orbit the Moon.

NASA finished assembling the main structural components for the first SLS rocket core stage on Sept. 19, 2019 at Michoud Assembly Facility in New Orleans. Photo: NASA

The rocket will then go on Pegasus to Stennis Space Center next year for a series of tests that will build like a crescendo over several months and climax with a full-duration test fire known as a ‘Green Test Run’, where the integrated rocket and engines will operate together for the first time, just as during an actual launch.

The test series will validate the vehicle as ready for flight, demonstrating that the engines, tanks, fuel lines, valves, pressurization system, and software all perform together as planned on launch day. Pathfinder practice ops were conducted on the test stand this past August to ensure workers are ready when the actual flight hardware arrives.

A SLS core stage pathfinder is positioned in the B-2 Test Stand at NASA’s Stennis Space Center to train and practice handling and lifting techniques needed for the core stage flight hardware when it arrives at Stennis for testing in 2020. Photo: NASA

Meanwhile, technicians at the SLS Artemis launch site at Kennedy Space Center have been practicing various launch processing operations with the SLS pathfinder over the last month. Arriving on the refurbished Pegasus barge, workers have been practicing offloading, moving and stacking maneuvers with the full-scale 228,000 pound mock-up in KSC’s iconic Vehicle Assembly Building (VAB), using important ground support equipment to train crews and certify all the equipment works properly.

“Experience is the best teacher,” said Jim Bolton, EGS core stage operations manager. “Pathfinders allow crews to practice lifting, accessing and transporting techniques that we prefer not to do for the first time with the flight hardware. Practicing with a pathfinder reduces risk and builds confidence.”

Technicians inside NASA’s Vehicle Assembly Building at Kennedy Space Center practice lifting a SLS pathfinder, a full-scale 228,000 pound mockup of the actual rocket, to gain experience before the actual flight hardware arrives for launch. Photo Credit: Jeff Seibert /

Another water deluge sound suppression system test was conducted at Artemis launch pad 39B recently too. During the 30-second test, about 450,000 gallons of water poured onto the Pad B flame deflector, the mobile launcher flame hole and onto the launcher’s blast deck. The system reached a peak flow rate of more than 1 million gallons per minute. 

The test was the first time the ground launch sequencer software that will be used on launch day was used to command launch support systems at Pad B from the Launch Control Center. The tests also included a nominal launch countdown flow and a single valve failure test flow to better characterize off-nominal system performance. Post-test analysis are currently underway in preparation for a final water flow test in the coming weeks, involving the hydrogen burn-off igniters.


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