After replacing leaky seals that halted a launch attempt of its new moon rocket last week, NASA said on Thursday that it hoped to try again later this month.
At a telephone news conference on Thursday, NASA officials announced two potential launch windows: Sept. 23 from 6:47 a.m. to 8:47 a.m. Eastern time and Sept. 27 from 11:37 a.m. to 12:47 p.m.
Before it can move ahead with another countdown, NASA will first conduct a test to ensure that the repairs worked by filling up the rocket’s huge tanks with liquid hydrogen and liquid oxygen. That test is scheduled for Sept. 17.
“I would not be surprised to see it slip a day or two,” Michael Bolger, the manager of NASA’s ground systems, said during the news conference.
He said that NASA would likely need four days between the test and the launch. “So if it slipped off the 17th for a couple of days, I think we could still protect the 23rd,” Mr. Bolger said.
NASA also needs a waiver for the batteries in the rocket’s flight termination system, which would destroy the vehicle if it went off course.
Without the waiver, the rocket, known as the Space Launch System, would have to be rolled back to the Vehicle Assembly Building for the flight termination system to be recharged and retested. That would likely delay the launch attempt, and the three-mile trip back to the building would add to the wear and tear on the rocket.
The flight termination system was originally certified for 20 days after installation and testing. NASA then asked for and received an additional five days, through Sept. 5, from the Eastern Range, the part of the United States Space Force that oversees rocket launches from Florida to ensure safety of people on the ground.
Now, NASA is asking for a longer extension.
“If they decide that it’s not the right thing to do, we obviously will support that and stand down and look for our next launch attempt,” Jim Free, NASA’s associate administrator for exploration systems, said. “But we still will proceed with the tanking test.”
The first launch attempt, on Aug. 29, was scrubbed after one of the rocket’s engines appeared to be insufficiently chilled, part of the preparations needed before ignition.
Afterward, analysis of the data indicated that the engine actually had been chilled and that a faulty sensor caused the misleading reading. Mission managers then moved forward with a second launch effort on Sept. 3. But during that countdown, a large hydrogen leak appeared in a connector along a fuel line attached to the rocket, leading to a second scrub.
The mission is part of NASA’s Artemis program, with the goal of sending astronauts back to the moon. This flight, which will not have any people on board, is a test of the rocket and Orion crew capsule, which will take a weekslong journey around the moon. Astronauts are to be aboard for the second launch, scheduled for 2024, and an actual moon landing is set to occur during the third mission in 2025.
Mr. Free said the new dates were chosen to avoid conflicts with NASA’s Double Asteroid Redirection Test mission, or DART. That spacecraft, launched last November, will collide with a small asteroid on Sept. 26, to see how well such high-speed crashes can change the direction of an asteroid — one of the possible strategies that might be employed if an asteroid were on a collision course with Earth.
On that day, NASA’s Deep Space Network of radio dishes will be busy communicating with DART. For an Artemis I launch on Sept. 23, the Orion spacecraft would not need much use of the network until after DART’s mission was complete. A launch on Sept. 27 would not conflict at all with other missions.
Mr. Free said the Artemis I team was also looking at a third date, but that needed to be coordinated with a planned SpaceX launch on Oct. 5 to carry astronauts to the International Space Station.