NASA's SLS hydrogen leak is a sign of the Artemis program's outdated technology

SLS on the launch pad.

NASA's Space Launch System didn't launch for the second time of asking on Saturday, September 3, due to a large hydrogen leak in a fuel line quick-disconnect fitting.

That leak is likely to delay the $23 billion SLS — NASA's most powerful rocket to date — by several weeks, pushing the launch into October.

Though the launch of SLS will kick off NASA's historic Artemis program, the latest delay is an indicator of the fact the space agency is relying on old technology that was originally designed for the Space Shuttle program. Experts have warned for years that the launch of SLS will suffer from difficulties that plagued the Shuttle program.

When will Artemis I launch?

The latest launch window ends today, Tuesday, September 6, and NASA has already announced it won't be attempting another launch during this window. The space agency is still troubleshooting the issue. Depending on the outcome, NASA will either keep SLS on the launch pad and perform a partial fueling test to confirm their fix works or send it back to the Vehicle Assembly Building for repairs.

The next launch window opens on September 19 and ends on October 4. However, SLS would have to be fixed on the pad for a launch during that timeframe to go ahead. NASA's plans to launch a new crew to the International Space Station on October 3 might also cause a scheduling conflict. That could mean the launch would be pushed back to the next launch window running from October 17 to October 31.

#Artemis Update: The team continues to troubleshoot, and plans to return with a variety of options early next week. We are standing down on any launch attempts through the current launch period, which ends Tuesday.

"This is an incredibly hard business," Artemis 1 mission manager Mike Sarafin explained, as per CBS News. "Our focus is on understanding the problem. ... We'll follow up next week when we have those options flushed out further."

Hydrogen issues go back to the Space Shuttle

NASA's SLS is the space agency's most powerful rocket to date. Once it launches, it will be capable of producing 9.5 million lbs of thrust to carry a payload capacity of 190,000 lbs (86 tons) up to low-Earth orbit (LEO).

Importantly though, the agency's newest launch system isn't a complete departure from what came before. The massive rocket is made primarily of adapted parts — such as its four RS-25 engines on the core stage — that were originally designed for the Space Shuttle program four decades ago.

NASA has faced criticism for using old technologies in the face of new reusable tech geared towards more sustainable and cost-effective rocket launches. The trouble is NASA is using the same main engines used for the Space Shuttle, a decision that was mandated when Congress wrote the authorization bill for NASA in 2010. These use liquid hydrogen propellant and liquid oxygen to serve as an oxidizer. As Ars Technica points out, the shuttle scrubbed nearly once every launch attempt throughout its lifetime, and the cause was often hydrogen issues.

Hydrogen is the lightest element, meaning it is surprisingly easy for leaks to occur. Though it is efficient and it provides better "gas mileage" when used in rocket engines, alternatives such as methane and kerosene are easier to manage and would invariably lead to fewer scrubs on the launch pad.

In an August interview with IE, former NASA Deputy Administrator Lori Garver said she pushed for the space agency to turn to private companies for the Artemis program, but the "forces of the status quo in government" were too strong. The result is a rocket that has gone more than $10 billion over budget and whose launch is more than five years late.

When it does eventually launch, though, it will pave the way for the crewed Artemis II mission and then Artemis III, which will use SpaceX's Starship as a lunar lander to send humans back to the surface of the moon. Success would mean the transition encouraged by Garver and many others is slowly but surely taking shape.

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