CAPE CANAVERAL—NASA pressed Sept. 1 to resolve the propellant loading issues that triggered the Aug. 29 scrub of the much-anticipated liftoff of the Artemis I mission.
After the scrub, the Artemis I Mission Management Team (MMT) and Launch Control Team targeted Sept. 3 at 2:17 p.m. EDT, the opening of a 2-hr. launch window, for a second launch attempt, assuming issues can be quickly resolved and the weather cooperates.
NASA’s last opportunity to launch Artemis I during its initial launch period will be Sept. 5 at 5:12 p.m., the opening of a 90-min. window.
This constraint is the requirement to periodically recertify the Space Launch System (SLS) flight termination system, which resides in the large rocket’s intertank and is designed to initiate the vehicle’s destruction should it veer off course after lifting off from Kennedy Space Center. In early August, NASA worked with Space Launch Delta 45, the U.S. Space Force unit that manages the Eastern launch range, to extend the duration between regular certifications of the termination system from 20 to 25 days—an activity that can only be accomplished if the SLS and Orion undergo a lengthy rollback from the launchpad to Kennedy’s Vehicle Assembly Building for technicians to gain access to the termination system.
The next Artemis I launch periods have been set for Sept. 19 to Oct. 4, and Oct. 17 to Oct. 31.
As the MMT prepared to convene Sept. 1, the weather outlook was improving. During the Aug. 29 launch attempt, the initial loading of 538,000 gal. of cryogenic liquid hydrogen and 196,000 gal. of liquid oxygen propellants was delayed for nearly an hour by stormy weather conditions that included lightning.
The Space Launch Delta 45 weather forecast included a 60% chance of favorable weather for Sept. 3 and 70% for Sept. 5. While rain showers with the prospect of lightning are possible each day, the storms are to be scattered and moving inland from NASA’s coastal launch complex, forecasters say.
With concurrence from the MMT to proceed, the Sept. 3 launch countdown will pick up at 4:37 a.m. EDT on that day, the launch minus 9 hr., 40 min. point, following a weather update and a poll among team members to proceed.
The Aug. 29 scrub was called at 8:33 a.m. EDT, the opening of the 2-hr. window, when the launch control team was unable to confirm the SLS first stage Engine 3, one of four RS-25 engines, had been thermally prepared for ignition with a “kick-start” procedure. The procedure flows -423F liquid hydrogen propellant to the four engines. Three of the engines registered -410F, which was close enough, but Engine 3 was 40 deg. warmer than the -420F objective, John Honeycutt, NASA’s SLS program manager, explained later.
A problem with the Engine 3 thermal sensor could not be ruled out, Honeycutt said.
Efforts during the Aug. 29 countdown to lower the Engine 3 temperature by increasing the pressure of the hydrogen flow led to another issue—a hydrogen leak in the 8-in. disconnect associated with an umbilical flow line in the tail service mast through which the hydrogen flows to the SLS from a launchpad storage tank.
Following the delay, the Launch Control Team assigned ground personnel to examine the tail service mast “purge can,” which houses the disconnect where the hydrogen leak was detected, though launch controllers were able to stop the leak by controlling the temperature and reversing the flow of propellant during the final hours of the first launch attempt.
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