According to NASA’s report, the problems that have resulted in the delays in the test programs for the Space Launch System core stage have reduced the available timeframe for preparation before the deployment of the mission. Initially, NASA was preparing to hold tests for the Space Launch System core stage at its Stennis Space Center early this month. This test involves filling the core stage with liquid hydrogen and oxygen fuel before making a timer that halts before the four RS-25 engines ignite. The test is the last stage before the overhaul static-fire test of the engines closes up on the entire Green Run test campaign. 

The early stages of this wet dress rehearsal test involve the engineers filling up the fuel tanks with liquid hydrogen to the stage before analyzing leaks or other system issues. When they were filling the propulsion system with liquid oxygen, the engineers discovered that the fuel was not as cold as it should be. The SLS stages manager at the Marshall Space Flight Center, Julie Bassler, stated that the problem that delayed the tests apart from this test was integrating the facility and core stage. The engineers simulated the causes of liquid oxygen, changing its temperature. They discovered that the process of sending the liquid oxygen through the test stand into the tank might have raised the temperature of the fuel due to motion. 

John Honeycut, the SLS program manager at the Marshall Space Flight Center, stated that although the temperature difference may seem minor, it is supposed to be as planned to minimize the formation of bubbles inside the fuel while entering the core stage. If the bubbles entered the core stage, then the bubbles would collapse above the combustion tanks generating energy as liquid oxygen relapses into the fuel system. Honeycutt reiterated that the problem has no association with the core stage. Neither is there a problem with the rocket, but the challenge is loading the liquefied oxygen and hydrogen fuels. Nevertheless, he is confident that the team of engineers conducting the procedure will rectify the problem before they resume the actual launch. NASA is evaluating the procedures that they can use to load the liquid oxygen to the core stage and rescheduling a repeat of the wet rehearsal to ascertain that the mission is ready. This move would convince the engineers to continue with the hot-fire tests before the end of this year.

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