NASA has decided to put a major component of the Space Launch System (SLS) rocket through a "Green Run" in the runup to the scheduled 2021 launch of the Artemis 1 lunar mission. The July 25 announcement by space agency Administrator Jim Bridenstine opens the way for the 212-ft-tall (65-m) core stage of the giant booster to be put through a series of major preflight tests that will include an eight-minute engine burn.
Building a new booster rocket is always a long, involved process and making one rated to carry astronauts is doubly so. By their very nature, liquid-fueled rockets are extremely complex and they need to handle enormous quantities of propellants that generate fantastic amounts of power.
In the case of the core stage and solid rocket boosters for the SLS, they will generate 8.8 million lb of thrust as the four main RS-25 engines consume 733,000 gal (2.7 million l) of liquid oxygen and liquid hydrogen in the first eight minutes of flight before handing over to the second stage. A key phase of testing these will take place on B-2 Test Stand at NASA's Stennis Space Center near Bay St. Louis, Mississippi, where the core stage will be installed for a static fire which won't see it leave the pad.
Previously, such firings involved test versions of a new rocket's avionics, cables, propulsion systems, and tanks, which would then be swapped for flight components for the actual missions. However, for the planned Green Run, NASA is taking a different approach.
Green Run means that the engineers are taking the new or "green" hardware and operating them all together in a "run" to test things like fueling, pressurization, and running the engines, tanks, fuel lines, valves, pressurization system and software through months of testing before the final igniting and running of the entire rocket.
What is different, is that these are actual flight components and not test versions. After the tests on the stand that also saw testing of the Saturn V and the Space Shuttle engines, the SLS core stage will be inspected, validated, refurbished, and sent on the NASA's Kennedy Space Center in Florida for assembly with the rest of the launcher for the Artemis 1 mission.
"The SLS core stage is an engineering feat that includes not only the largest rocket propellant tanks ever built but also sophisticated avionics and main propulsion systems," says Lisa Bates, SLS deputy stages manager. "While the rocket is designed to evolve over time for different mission objectives, the core stage design will remain basically the same. The Green Run acceptance test gives NASA the confidence needed to know the new core stage will perform again and again as it is intended.
"With Green Run, we verify each individual component operates well within the core stage system. It's more than testing. It's the first time the stage will come to life and be fully operational from the avionics in the top of the core stage to the engines at the bottom."
Source: NASA