NASA will not attempt to launch its Space Launch System in the coming days, the agency announced today, skipping potential launch windows on Monday and Tuesday. The announcement comes after two scrubbed launch attempts of the massive rocket, and will likely result in a delay of several weeks.

August 29th, 2022 was supposed to be the debut launch of the Space Launch System (SLS). That launch attempt was scrubbed after engineers noticed an issue with the temperature of one of the rocket’s four engines. Today, a second launch attempt was foiled by a persistent hydrogen leak that Artemis mission manager Michael Sarafin described as “large,” in a press conference after the scrub. A small hydrogen leak was also noticed during the attempt on the 29th, but this was much larger.

The launch, whenever it happens, will be the first for NASA’s SLS, a very expensive, extremely delayed rocket which has been in development for over a decade. The rocket was set to launch an uncrewed capsule called Orion on a mission called Artemis I. The mission is designed to serve as a test flight, paving the way for future missions which will carry astronauts to the Moon.

NASA hasn’t announced when its next launch attempt of Artemis I will be, but expects to have a better idea within a few days. Engineers are focused on part of the fueling system that helps send liquid hydrogen fuel into the rocket, and which can quickly disconnect from the rocket after fueling. This “quick disconnect” has a seal around it that is designed to keep hydrogen from leaking out, which is referred to as “soft goods”. One solution that is being considered is removing and replacing the soft goods around the quick disconnect.

The engineering teams are currently trying to figure out whether it will be better to do this replacement and troubleshoot any other issues back in the Vehicle Assembly Building (VAB) or if they should stay on the pad. There are risks and benefits to both approaches. As noted by Sarafin, if NASA stayed on the pad, they could test the system at cryogenic temperatures, which would give them a better idea of how it would behave during a real launch. The downside is that NASA would also need to build an environmental enclosure to stay at the pad. If they went back into the VAB, the building itself would act as an environmental enclosure. But while NASA could replace and test the problematic parts inside the VAB, it can only do it at ambient temperature — not cryogenic.

Speaking soon after the second launch scrub on Saturday, NASA Administrator Bill Nelson said if the SLS rolls back into the VAB for repairs, the next launch attempt would most likely happen in mid to late October, after a planned crew mission to the International Space Station takes off earlier that month. The process of rolling the megarocket back to the VAB takes several hours.

There’s another complication too. When the rocket rolled out to the pad on August 16th, another timer started. NASA had 20 days in which to launch the rocket before it would have to be rolled back in order to test the batteries in the rocket’s flight termination system. The termination system is part of the rocket that the Space Force can use to destroy the rocket if something goes wrong during the launch and flight. NASA got approval to extend that to 25 days, but that time is almost up. Unless NASA gets another extension, it will have to travel back to the VAB anyways.

“We do not launch until we think it’s right,” NASA administrator Bill Nelson said during a press conference. “So I look at this as part of our space program, of which safety is at the top of our list.”