Cosmic Space

NASA rolls back its SLS moon rocket to make repairs

NASA brought its Space Launch System rocket back to one of the world’s biggest repair shops — the 526-foot-tall Vehicle Assembly Building at Kennedy Space Center in Florida — to fix some flaws that turned up during rehearsals for a mission beyond the moon.

It took 10 hours to roll the 322-foot-tall, 3.5 million-pound rocket on its mobile launch platform from Launch Complex 39B to the VAB. The 4-mile journey, which made use of a giant crawler-transporter handed down from the Apollo and space shuttle programs, was basically a rewind of the rocket’s trip to the pad on March 17-18.

NASA had hoped to conduct a “wet dress rehearsal” for the launch of the SLS and its Orion deep-space capsule on an uncrewed trip around the moon. That mission, known as Artemis 1, is meant to set the stage for a crewed round-the-moon mission in 2024 and the first crewed landing on the moon since the Apollo era in 2025 or 2026.

Unfortunately for NASA, the practice runs came across some issues that need to be addressed in the days and weeks ahead.

On April 3, the launch pad team ran into problems with the fan-based pressurization system for the mobile launcher. The next day, the countdown was stopped when the launch pad team faced difficulties while loading liquid oxygen into a tank on the core stage.

The problems continued on April 7, when a faulty helium check valve ruled out filling the upper stage’s tanks with super-chilled hydrogen and oxygen propellants.

After troubleshooting the problem, mission managers decided to skip fueling the upper stage and simply rehearse filling the core stage’s tanks. But during yet another practice run on April 14, the team detected a small leak in a tail service mast umbilical line — basically, a plumbing system that’s meant to fill up the core stage’s liquid-hydrogen tank. Issues also cropped up with the pad’s supply of nitrogen gas, which is used to support tanking operations.

NASA decided to bring the SLS back to the VAB to replace the helium valve, fix the leak and upgrade the nitrogen system.

Mission managers had hoped to launch the Artemis 1 mission in June, but now the timing for launch is up in the air. NASA doesn’t want to proceed with launch until it makes the repairs and completes a full-scale dress rehearsal, all the way down to the moment before ignition.

“We still have a lot to do with wet dress rehearsal,” NASA Associate Administrator Bob Cabana said. “The team is evaluating options. We’ll make a decision here in the not too distant future of what the best path forward is.”

Even if everything goes right, Artemis 1 isn’t likely to lift off for the moon before August, Cabana said.

By Alan Boyle

Mastermind of Cosmic Log, contributor to GeekWire and Universe Today, author of "The Case for Pluto: How a Little Planet Made a Big Difference," past president of the Council for the Advancement of Science Writing.

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