Chance of Moon landing in 2024 ever slimmer if test flight this year is delayed Richard Speed Mon 1 Feb 2021 // 13:56 UTC Share Copy Hopes of a launch of NASA's Space Launch System (SLS) in 2021 have been dealt a further blow by an admission that a second Green Run hot fire test is required for the SLS core stage. The Boeing-led core stage for NASA's monster Moon rocket arrived at the Stennis Space Center, Mississippi, over a year ago and was mounted in the B-2 test stand for a succession of check-outs known as the Green Run. These culminated in a firing of all four Shuttle-derived RS-25 engines in order to simulate a launch.