KENNEDY SPACE CENTER, Fla. - During its fourth attempt this year, NASA successfully completed fueling its mega moon rocket with super-cold propellant that will eventually return humans to the moon as part of a launch dress rehearsal.
Artemis-1 Launch Director Charlie Blackwell-Thompson gave the "Go" Monday around 8:45 a.m. to begin loading 700,000 pounds of cryogenic fuel into the 32-story Space Launch System rocket with the Orion spacecraft on top at launchpad 39B.
Monday's fueling operations and countdown are part of a test known as the wet dress rehearsal and was previously attempted four times in April. Still, after several hardware issues cropped up, the rocket was rolled back into the Vehicle Assembly Building for repairs.
Operations began around 7 a.m. Monday. Meteorologists with the Space Force's 45th Weather Squadron forecast favorable conditions for the Monday test. There must be a less than 20% chance of lightning within 5 nautical miles from the launchpad during the first hour of fuel loading.
The count was put on hold as teams worked through an issue with a backup supply of gaseous nitrogen.
Assistant Launch Director Jeremy Graeber said the team had to replace a controller for one of the two gaseous nitrogen valves after an issue this morning. There are two valves, each with a controller, which allows for more opening or closing.
"We need to have redundancy, a primary and a backup," Graeber said.
After the delays, preparations for fuel loading began at 9:28 a.m. as the countdown resumed.
First, fuel lines to the core stage were cooled to prepare for the extremely-cold propellant. Next, liquid oxygen was slowly loaded into the rocket's core stage. After LOX-load was well underway, the lines were cold for liquid hydrogen that began flowing into the rocket's core stage.
The liquid hydrogen loading was problematic for one of the previous wet dress rehearsal attempts after detecting a leak. It appears that was not a problem on Monday, as fueling proceeded into the afternoon.
Both tanks were more than 60% complete by noon, and by 1:30 p.m., both LOX and liquid hydrogen tanks in the core stage were full. The teams next moved to fill the upper stage, known as the ICPS (Interim Cryogenic Propulsion Stage), with both fuel types.
Another leak in a new place
During the propellant loading, engineers conduct leak checks along the way. During the upper stage fueling, engineers noticed a leak in a quick disconnect line for the core stage and halted fueling momentarily to troubleshoot the issue.
"The team is pursuing a potential fix for the core stage quick-disconnect leak," NASA's Exploration Ground Systems said.
Just before 6 p.m., NASA officials said all rocket stages were fueled. The core stage has 196,000 gallons of liquid oxygen at minus 297 degrees Fahrenheit and 537,000 gallons of liquid hydrogen. This marked the first time the SLS was fully fueled.
However, the leak was still not resolved. It's unclear if the test will be complete on Monday, marking NASA's fourth attempt since April.
After fueling, the launch team worked through the countdown like they would on launch day. However, the rocket will stay firmly on the ground at the end of the countdown.
When the test is complete, NASA is expected to announce a launch date for Artemis-I.
During a call with reporters last week, NASA associate administrator for Exploration Systems Development Mission Directorate Jim Free estimated the agency would look at the launch window from Aug. 23 to Sept. 6.
NASA is streaming the test live at NASA.gov with views of the massive rocket and commentary. This story will be updated throughout the wet dress rehearsal.