WASHINGTON – NASA plans to complete the Green Run test campaign for the core phase of the Space Launch System with a fire test scheduled for mid-January.
NASA announced on January 5 that it had scheduled the test for static fire, where the nuclear phase’s four RS-25 engines fired for a 493-second full-time combustion, for January 17 at the Stennis Space Center in Mississippi. .
NASA made the decision after evaluating the data from a wet dress rehearsal test on December 20, where the core stage was loaded with liquid hydrogen and liquid oxygen propellants and went through a practice count. The countdown was supposed to last up to 33 seconds before ignition, but rather stopped a few minutes before it did, NASA said in a Dec. 21 statement.
The early end of the wet dress rehearsal, NASA said, was caused when a valve shut off a fraction of a second of the predicted time. “The team has corrected the timing and is ready to proceed with the final test of the Green Run series,” the agency said.
The valve issue was the only major issue NASA reported during the wet dress rehearsal, the seventh in a series of tests in the overall Green Run campaign. “During our wet dress rehearsal Green Run test, the core phase, the stage controller and the Green Run software ran flawlessly, and there were no leaks when the tanks were fully loaded and refilled for about two hours,” Julie Bassler, SLS Stages- driver at NASA, said in the agency’s statement. “Data from all the tests so far has given us the confidence to continue with the hot fire.”
If the January 17 date for the fuel test takes place, it will be almost exactly a year after NASA installed the core stage at the B-2 test stall at Stennis. At that point, the agency was hoping to complete the Green Run tests by late summer. However, a two-month shutdown of Stennis, caused by the coronavirus pandemic, along with a series of transient tropical weather systems, delayed the series of tests.
Technical problems with the core stage and the test equipment also contributed to the delays. NASA only tried the nuclear phase’s wet clothing rehearsal on December 7, but stopped it when liquid oxygen flowing into the stage was too hot. Agency officials said it was the problem with the propellant loading, and not with the nuclear phase itself.
Once the Green Run test is complete, NASA will send the nuclear phase to the Kennedy Space Center to be integrated with the other elements of the SLS and the Orion spacecraft for the Artemis 1 mission. NASA planned to launch Artemis 1 by the end of 2021, but the latest delays in the Green Run eliminated the margin in the schedule for that date except.
“We’re getting to a point where we have very little margin left in the schedule relative to our commitment to our delivery date,” NASA SLS program manager John Honeycutt said on Dec. 10 after the first attempt to feed the wet. dress rehearsal. “The margin we built into the Green Run schedule is getting pretty slim.”