WASHINGTON – NASA managers said a rollback of the Space Launch System from its launch pad after three truncated countdown tests will allow them to address issues both on the pad and with the vehicle, but that it was too early to predict what would happen. would do to the schedule for the vehicle’s first launch.
NASA announced late on April 16 that it would be moving the SLS back from Launch Complex 39B to the Vehicle Assembly Building (VAB). Doing so, the agency said then, would buy them time to improve the supply of nitrogen gas on the platform that caused problems with two of the three tank tests.
The announcement came as something of a surprise, as at a briefing just over 24 hours earlier, NASA managers expressed optimism about finding the source of a hydrogen leak that wiped out the third countdown attempt on April 14. . So they predicted that they might make another attempt to fuel the core stage with liquid hydrogen and liquid oxygen propellants and count down as early as April 21.
The need to correct the nitrogen gas problem on the platform prompted the change in plans, Charlie Blackwell-Thompson, NASA’s Artemis launch manager, said in a call with reporters on April 18. There were gas supply problems both at the start of propellant loading operations and also after flushing, when the core stage was emptied.
“When we looked at the timelines associated with that and took that new data,” he said of the nitrogen updates, “it made us see what we could do on the platform and if it made sense to stay on the pad.” The decision, he said, was to move the SLS back to VAB while crews upgrade the nitrogen system.
That upgrade involves putting new equipment online at a facility just outside the Kennedy Space Center. “Those are already in the plant. They are already installed. It’s just a matter of tying them down,” he said. That work does not affect other sites in the center, such as the neighboring Launch Complex 39A, which also uses nitrogen gas for launch operations.
The new equipment provides a “more robust capability” to deliver the higher volumes of nitrogen gas needed for SLS applications such as umbilical line purging, said Tom Whitmeyer, NASA deputy associate administrator for common exploration systems development.
Agency officials did not identify the company that provides the nitrogen used at the center, referring to it only as the “nitrogen supplier.” However, Air Liquide operates a plant just outside KSC’s gates that generates nitrogen that is piped to various launch pads and other facilities at the center, according to a NASA website.
Workers are now preparing to roll back the SLS and its mobile launch pad to the VAB, with the pad’s move into the building tentatively scheduled for April 26, depending on the weather. Once at the VAB, technicians will work to both repair the hydrogen leak found in the April 14 test and repair a faulty helium check valve in the rocket’s upper stage.
Blackwell-Thompson said initial checks on the platform failed to identify the source of the hydrogen leak on the mobile launcher. Additional work to locate the leak will wait until the vehicle returns to the VAB.
How long SLS will remain GVA remains to be seen. A “quick turn” option would focus on repairing the hydrogen leak and replacing the check valve before returning to the platform for another wet dress rehearsal. A second option would add some additional work that NASA must complete before SLS is ready for launch that was planned after the wet dress rehearsal. A third option would prepare the vehicle for flight at the VAB, then deploy for a wet dress rehearsal followed by the launch of Artemis 1.
NASA officials said they had yet to decide which option to follow or program the implications of those options. Blackwell-Thompson said it was too early to estimate a minimum amount of time SLS would stay at VAB before coming back out. The first option would likely have the vehicle on the VAB “within a few weeks,” she said.
However, the reversal makes it unlikely that SLS will be ready to launch in a window running from June 6 to June 16. “The previous June window is challenged at this point,” Whitmeyer said. The next window opens June 29 and runs through July 12, with a cutoff between July 2 and July 4.
However, he stressed that NASA would conduct a full-scale tanking test and practice a countdown before attempting a launch. “We’re absolutely going to do a wet dress rehearsal,” he said. “It’s just a question of what’s the right time and what’s the right way to do it.”