SLS rollback
The SLS, seen here rolling back to the VAB in late April, will return to the pad in early June for another countdown test later in the month. Credit: NASA/Aubrey Gemignani

WASHINGTON — NASA is gearing up to perform another practice countdown of the Space Launch System in mid-June as it completes repairs to the vehicle from previous tests.

NASA said May 20 it expects to roll out the SLS from the Vehicle Assembly Building at the Kennedy Space Center to Launch Complex 39B in early June for the next attempt at a wet dress rehearsal (WDR), where the vehicle is filled with liquid oxygen and liquid hydrogen propellants and goes through a countdown that stops just before ignition of the core stage’s four RS-25 engines.

NASA made three attempts at completing a WDR at the pad in April, but stopped all three early after a series of problems. The agency rolled the SLS back to the VAB April 26 to fix both issues with the vehicle and its ground systems as well as with the supply of nitrogen gas at the pad.

In the statement, NASA said workers have completed work on the vehicle, including replacing a helium check valve in the upper stage and fixing a hydrogen leak in an umbilical. Crews also modified “purge boots” on umbilical lines leading into the upper stage to protect them from the elements.

NASA confirmed that Air Liquide, the contractor who provides nitrogen gas for the launch pad and other facilities at KSC, had completed upgrades that will ensure there will be enough gas available to support SLS operations.

Janet Petro, director of KSC, said at a May 18 briefing that a test of the nitrogen gas system took place the previous night and went well. “We’re feeling really good about rolling out in early June and completing the wet dress.”

NASA did give a date for the next WDR attempt, other than about 14 days after rollout. At the May 18 briefing, though, NASA Associate Administrator Bob Cabana said he estimated the next attempt would be June 18 to 20.

NASA officials had previously said they would not set a launch date for the Artemis 1 uncrewed mission until after completion of the WDR and assessment of the work needed to get the vehicle ready for flight. However, NASA Administrator Bill Nelson told House appropriators May 17 he now expected it to launch in August.

An updated schedule released by NASA May 16 said the next launch window for the Artemis 1 mission is July 26 to Aug. 10, although with no launches possible on Aug. 1, 2 and 6. The following window opens Aug. 23 and runs through Sept. 6, but with no launches on Aug. 30 through Sept. 1. Launch windows are constrained by several factors, including availability of trajectories for the SLS to send the Orion spacecraft to the moon and return for a splashdown in daylight hours off the California coast.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...