NASA had planned to launch Artemis 1 on Sept. 23 or Sept. 27, using a Space Launch System (SLS) megarocket to carry an uncrewed test trip to lunar orbit. However, the agency said in a blog post on Monday evening (Sept. 12) that the earlier date is no longer in play; it is now eyeing Sept. 27 for the Artemis 1 departure, with a probable backup date of Oct. 2.

"The updated dates represent careful consideration of multiple logistical topics, including the additional value of having more time to prepare for the cryogenic demonstration test, and subsequently more time to prepare for the launch," NASA officials wrote in a blog post. "The dates also allow managers to ensure teams have enough rest and to replenish supplies of cryogenic propellants."

Artemis 1 was anticipated to have already ascended. On Aug. 29, NASA attempted to launch the mission but was unsuccessful due to an unusual temperature reading in one of the first-stage RS-25 engines of the SLS. The mission crew quickly determined that the problem was a defective temperature sensor and prepared the SLS and Orion for a second attempt on Sept. 3. But a leak in the liquid hydrogen propellant also prevented that launch.

The leak happened at a "quick disconnect," which connects the SLS core stage to a fuel line coming from the rocket's mobile launch tower. According to NASA officials, the Artemis 1 team changed two seals surrounding the quick disconnect last week and completed other repair work related to the issue over the weekend.

NASA is now preparing for an SLS fueling test, in which supercold propellant will be pumped into the SLS to demonstrate that the leak has been repaired. The EPA had planned to conduct the test on Sept. 17, but it has now been put back to no sooner than Sept. 21.

The Artemis 1 stack is still at NASA's Kennedy Space Center in Florida's Pad 39B, but it might eventually need to roll back to the massive Vehicle Assembly Building (VAB). The flight termination system (FTS) for Artemis 1 was certified by the U.S. Space Force for just a 25-day period, and that time has now passed. The U.S. Space Force is in charge of managing the Eastern Range for rocket launches.

NASA has requested an extension for the FTS's certification, which is designed to destroy the Artemis 1 stack if it deviates from its intended path during liftoff. If that request is denied, the vehicle will have to be rolled from Pad 39B to the VAB, which is the only area where the recertification testing may take place.

NASA has already received one such FTS extension, extending it from 20 to 25 days.