SLS Green Run Tests Slip, But November 2021 Remains Artemis I Target

NASA officials said today they are still aiming towards the first launch of the Space Launch System (SLS) in November 2021 even though the last two core stage tests in the Green Run series have been delayed. The seventh of eight tests was paused earlier this week because of operational issues in loading liquid oxygen. That will push the date for delivering the core stage to Kennedy Space Center until February, squeezing the rest of the schedule to get ready for launch.

NASA SLS Program Manager John Honeycutt told reporters today that while loading propellant into the core stage during the “wet dress” rehearsal test, the liquid oxygen (LOX) did not chill down to the requisite temperature. He and STS stages manager Julie Bassler are confident it is an operational problem in how the LOX is being loaded, not an issue with the core stage itself.

SLS is NASA’s Saturn V-class rocket that it will use to launch astronauts in Orion spacecraft to the Moon and someday Mars.  The core stage is the centerpiece of SLS, powered by four RS-25 engines left over from the space shuttle program.  In the wet dress test, the stage is filled with LOX and liquid hydrogen precisely to discover any issues like this.

Bassler said the goal was to get the LOX temperature down to -290.57º Fahrenheit and “we didn’t quite get there on Monday.”  The temperature was -286.67º F instead, so they decided to pause the test to find out why and remedy it.  They are still looking into it and hope to resume the test next week.

Once it clears this test, the propellant will be removed, engineers will study the data, and, if all is well, move on to the eighth and final “hot fire” test where not only will the stage be fueled, but the engines fired for the full eight minutes that would be needed to reach orbit. In this case, it will be held down on a gigantic test stand at Stennis Space Center in Mississippi.  Honeycutt said they are eyeing the last week of December for the hot fire test.

The first flight of SLS has been delayed again and again.  In 2014, NASA committed to the first launch in November 2018. That slipped to December 2019-June 2020, then to mid-late 2021.  Most recently, NASA has been saying November 2021.

Honeycutt acknowledged there is little margin left in the schedule to be able to ship the core stage to Kennedy Space Center (KSC) even by February. The original plan was to ship it last month, allowing a year for all the SLS components to be at KSC for mating and integrated testing before launch.  All the other pieces — the Solid Rocket Boosters, Interim Cryogenic Upper Stage, Orion spacecraft, and other hardware — are there already.

Mission success and astronaut safety are the drivers, Honeycutt stressed, not the schedule.

No one will be aboard this first flight, designated Artemis I, the first in NASA’s Artemis program to return astronauts to the Moon. The first flight with a crew, Artemis II, is planned for 2023.  Under the current schedule Artemis III will launch in 2024 and deliver astronauts to lunar orbit where they will board Human Landing  Systems to travel down to and back from the lunar surface for the first time since 1972.

Some of the delays this year have been due to facility closures at Stennis due to COVID-19 and several hurricanes.