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SLS Core Stage Green Run Testing Overview

NASA’s SLS Green Run Tests Core Stage for Artemis I

Core Stage for NASA Moon Rocket Ready for SLS Green Run Testing
The massive core stage for NASA’s Space Launch System (SLS) rocket is in the B-2 Test Stand at NASA’s Stennis Space Center near Bay St. Louis, Mississippi, for the core stage Green Run test series. NASA and Boeing, the core stage lead contractor, installed the stage into the test stand in January 2020. The core stage Green Run test series is an important step toward safely launching SLS and NASA’s Orion spacecraft beyond Earth’s orbit forward to the Moon for the agency’s Artemis program. The 212-foot-tall rocket stage — the largest stage the agency has ever produced — contains the cryogenic liquid hydrogen and liquid oxygen tanks that will feed four RS-25 rocket engines, along with the vehicle’s avionics and flight computers. The comprehensive test campaign will validate the core stage design and ensure it’s ready for the first and future Artemis missions to the Moon. Credits: NASA

NASA is in the final phase of a series of tests to bring the Space Launch System (SLS) rocket core stage to life for the first time, allowing engineers to evaluate the new complex stage that will launch the Artemis I lunar mission.

This testing will reduce risks for, not only the first flight, but also for the Artemis mission that will land astronauts on the Moon in 2024.

Testing started in this January and will wind up this fall.  A series of tests conducted over the last year have successfully checked out the stage’s systems and operations. These tests and checks collectively called Green Run will culminate this fall in a test fire  that will last up to 8 minutes replicating the stage’s first launch.

The Green Run test series, conducted in the historic B-2 Test Stand at NASA’s Stennis Space Center near Bay St. Louis, Mississippi, is a collaborative effort between the SLS program, the Stennis test team, core stage manufacturer Boeing and engine manufacturer Aerojet Rocketdyne. Green Run testing was briefly suspended in March when Stennis Space Center went to Stage 4 on the Agency Response Framework in response to a rise in COVID-19 cases in the area near Stennis.

Using the appropriate safety measures, NASA resumed testing operations in May.

With more than half the tests complete, the core stage is nearing its eighth and final Green Run test: a complete activation of all the core stages systems that will result in a hot fire of all four RS-25 engines to generate 1.6 million pounds of thrust.

Made specifically for Green Run, engineers at Marshall designed software based on the Artemis I SLS flight. A special stage controller will be used to simulate the Launch Control Center operations that will control the actual launch at Kennedy Space Center in Florida.

Green Run tests minimize risk to the core stage and ensure the stage satisfies design objectives and validates design models:

  • Test 1- Modal Test: The first test in the Green Run series, a modal test was conducted in January. This test used shakers to impart dynamic forces on the suspended stage to identify primary bending modes of the stage. Information from the modal test will help engineers verify vehicle models needed for the operation of the rocket’s guidance, navigation and control systems.  
  • Test 2- Avionics: The rocket’s avionics, which are distributed throughout the stage, where activated and checked out. This includes not only flight computers and electronics that control the rocket but also those that collect flight data and monitor the overall health of the core stage.
  • Test 3- Fail-Safes: Engineers inspected all the safety systems that shut down operations during testing. During this test, they simulated potential issues.
  • Test 4- Propulsion: The was the first test of each of the main propulsion system components that connect to the engines. Command and control operations where verified, and the core stage was checked for leaks in fluid or gas.
  • Test 5- Thrust Vector Controls: Engineers ensured the thrust vector control system can move the four engines and check all the related hydraulic systems.
  • Test 6- Countdown: This simulated the launch countdown, including step-by-step fueling procedures. Core stage avionics where powered on, and propellant loading and pressurization was simulated. The test team exercised and validated the countdown timeline and sequence of events.
  • Test Case 7- “Wet” Dress Rehearsal: Engineers will demonstrate loading, controlling and draining more than 700,000 gallons of cryogenic propellants into the two test stand run tanks and then returning the stage to a safe condition.
  • Test Case 8- Hot Fire: The core stage’s four RS-25 engines will operated for up to 8 minutes, generating 1.6 million pounds of thrust, the amount of thrust the engines produce at sea level on the launch pad at liftoff.

After the hot fire test, engineers will refurbish the core stage and configure it for its journey to Kennedy for launch preparations. The next time the RS-25 engines fire, the SLS will launch in an epic debut of Artemis I — the first in a series of increasingly complex missions that will enable human exploration to the Moon and Mars.

Green Run Checlist #8
Green Run Checlist #8

Learn more about Green Run.