NASA's next attempt to launch its new megarocket on a test flight to the moon could lift off by Sept. 23, but only if the agency fixes a leak and receives a critical waiver from the U.S. Space Force.
Jim Free, NASA's associate administrator for exploration systems development, said today (Sept. 8) that NASA's Artemis 1 moon mission launch — the debut of its giant Space Launch System (SLS) rocket — could lift off on Sept. 23 or Sept. 27. Those launch dates depend on a number of requirements, including NASA securing a waiver to extend the time needed to check batteries on the SLS' flight termination system (FTS), which is designed to destroy the rocket if it veers off course during launch.
The U.S. Space Force, which oversees the Eastern Range used for Florida rocket launches, requires NASA to test the FTS every 25 days, a process that requires the 322-foot-tall (98 meters) rocket to leave the launch pad and roll back to its hangar. Extending that time frame could allow NASA to avoid weeks of additional delay that would push the Artemis 1 launch into October.
Free said Artemis 1 mission managers submitted a waiver request to the Eastern Range this week. "After meeting with us several times, they've been very gracious and understanding of what we're trying to do," he said in a teleconference today. "Our job is to live to their requirements. That is their range. And it's our job to comply with their requirements."
Free did not reveal how long of an extension NASA is seeking. The agency already had secured one such FTS waiver, pushing the limit from 20 to 25 days.
Launch waivers and fuel leaks
Artemis 1 is NASA's first mission of the Artemis program to return astronauts to the moon by 2025. It is an uncrewed flight that will test the SLS megarocket and its Orion spacecraft to verify that both are ready to fly astronauts. The first crewed Artemis mission, Artemis 2, will fly astronauts around the moon in 2024, with the Artemis 3 crewed landing to follow a year later. All of that depends on a successful test flight of Artemis 1.
Even with the FTS test waiver, NASA has its hands full trying to get Artemis 1 ready for what will be its third launch attempt. NASA first tried to launch the mission on Aug. 29 but stood down due to an engine cooling issue that was traced to a bad sensor. A persistent liquid hydrogen leak that beat three attempted fixes led to the Sept. 3 launch scrub.
NASA must fix that leak by replacing a seal around an 8-inch (20 centimeters) fuel line on the SLS' core booster. The agency is also working on a smaller fuel connector that saw a different leak on Aug. 29. That work is ongoing this week at the Artemis 1 rocket's Pad 39B launch site at Kennedy Space Center in Florida.
A kinder and gentler fueling approach
The Artemis 1 SLS rocket must then pass a fueling test to check if the seal fix worked. That test is currently scheduled for no earlier than Sept. 17, but the schedule is tight, Mike Bolger, NASA's Exploration Ground Systems manager, said in today's press conference.
"I would not be surprised to see it slip a day or two," Bolger said. Even if it slips a few days, NASA would still be able to pursue the Sept. 23 or Sept. 27 windows, he added.
NASA has not confirmed if an "inadvertent" manual command that briefly overpressurized the hydrogen fuel line caused the leak, but the agency is investigating the incident. Bolger said new manual processes replaced automated ones during the second attempt and the launch team could have used more time to practice them.
"So we didn't, as a leadership team, put our our operators in the best place we could have," Bolger said. During the Sept. 17 fueling test, NASA will try out a slower, "kinder and gentler" process that should avoid such events.
"We all own the process," Free added. "As far as I was concerned, everybody's finger was on that switch."
Fueling the Artemis 1 SLS rocket with its 736,000 gallons (2.79 million liters) of super-cold liquid hydrogen and liquid oxygen propellant has been a challenge for NASA. Before the two launch attempts, the agency performed four test runs, called "wet dress rehearsals," but didn't manage to check all the desired boxes during any of them.
The next fueling test will be used to check that the leak repairs worked, Bolger said.
"This is the first time we're operating this vehicle," Free said, adding that NASA saw fueling challenges during its space shuttle and Apollo programs. "There are challenges when you try and do this."
Finally, NASA must fit the Artemis 1 launch in when its Deep Space Network communications assets can support the moon flight.
NASA's DART asteroid probe is scheduled to crash into a small asteroid on Sept. 26 and will need to use the Deep Space Network to relay its discoveries back to scientists on Earth. NASA's Artemis 1 launch dates of Sept. 23 and Sept. 27 should avoid any conflict with that mission, Free said.
Meanwhile, SpaceX is planning to launch its next NASA astronaut crew mission, called Crew-5, to the International Space Station on Oct. 3. That's another constraint for when Artemis 1 can fly, Free said.
NASA technically has launch windows for Artemis 1 that run from Sept. 16 to Oct. 4, and then again from Oct. 17 to Oct. 31, with some cutout days in each window.
If NASA is able to pursue a Sept. 23 launch for Artemis 1, liftoff would be scheduled for 6:47 a.m. EDT (1047 GMT) during a 120-minute window. The mission would return to Earth on Oct. 18.
A Sept. 27 launch for Artemis 1 would lift off at 11:37 a.m. EDT (1537 GMT) at the start of a 70-minute window. A launch on that day would lead to a return to Earth on Nov. 5, Free said.