After a shorter than scheduled final test of the Space Launch System (SLS) Core Stage I back in January, NASA then targeted Thursday, February 25 for the new date for the second hot fire test.

But a valve issue discovered on Sunday during a systems check caused the space agency to delay the test at Stennis Space Center near Bay St. Louis, Mississippi. 

NASA said the issue is with one of the eight valves, known as a prevalve, that is part of the core stage's main propulsion system. It supplies liquid oxygen to an RS-25 engine.

The valve is being inspected by both NASA and Boeing, the core stage's lead contractor. Vacco manufactures the valve and is based in El Monte, California. 

During a media teleconference on Friday, February 19, Tom Whytmeyer, the deputy associate administrator for exploration systems development at NASA, said that a successful second hotfire test this month should allow them to launch Artemis I in late 2021. 

He said following the test, they have 30 days to refurbish the core stage and then ship it to Kennedy Space Center. 

A new date for the hot fire test is being determined.