Artemis II moon rocket fueling test runs into problems with hydrogen leak

A hydrogen leak at the base of NASA’s Artemis II moon rocket Monday threw a wrench into a carefully planned countdown “wet dress” rehearsal, but engineers were able to manage a workaround and the test proceeded toward a simulated launch.

Whether mission managers will be able to clear the rocket for an actual launch as early as Sunday to propel four astronauts on a flight to the moon will depend on the results of a detailed overnight review and post-test analysis. NASA only has three days — Feb. 8, 10 and 11 — to get the mission off this month or the flight will slip to March.

Given no other major problems cropped up with the rest of the countdown, it would appear NASA has a shot at a Super Bowl Sunday launch, but NASA did not reveal how far out of limits the leak was or whether any repairs might be needed.

The practice countdown began Saturday evening — two days late because of frigid weather along Florida’s Space Coast — and after a meeting Monday morning to assess the weather and the team’s readiness to proceed, launch director Charlie Blackwell-Thompson cleared engineers to begin the remotely controlled fueling operation. 

The test got underway about 45 minutes later than planned, but it initially appeared to be proceeding smoothly as supercold liquid oxygen and hydrogen fuel were pumped into the Space Launch System rocket’s first-stage tanks. Shortly after, hydrogen began flowing into the rocket’s upper stage as planned.

But after the first-stage hydrogen tank was about 55% full, a leak was detected at an umbilical plate where a fuel line from the launch pad is connected to the SLS rocket’s first stage. After a brief pause, engineers resumed fuel flow but again cut it off with the tank about 77% full.

After more discussion, they decided to press ahead on the assumption the leak would decrease once the tank was full and in a replenishment mode when flow rates were reduced. And that turned out to be the case.

“NASA teams have completed filling the core stage of the SLS rocket with liquid hydrogen,” NASA said in a brief web update at 4:45 p.m. EST. “Engineers continue to watch the leak at the interface of the tail service mast umbilical, but the liquid hydrogen concentration in the umbilical remains within acceptable limits.”

The countdown was timed for a simulated launch at 9 p.m., but the test ran longer than originally planned. As of 9:40 p.m., the countdown was in an extended hold at the T-minus 10-minute mark.

The SLS is the rocket NASA plans to use to send Artemis astronauts to the moon aboard Orion crew capsules. It is the most powerful operational launcher in the world, a towering 332-foot-tall rocket powered by two strap-on solid fuel boosters and four main engines burning liquid oxygen and hydrogen fuel that generate 8.8 million pounds of thrust at liftoff.

Artemis II commander Reid Wiseman, Victor Glover, Christina Koch and Jeremy Hansen are hoping to launch atop the SLS rocket as early as Sunday night for a nine-day two-hour flight around the moon and back. They planned to fly to Florida on Tuesday to begin final preparations, but that could change depending on the results of the countdown review.

The SLS rocket’s first and so far only mission came in 2022 when it was launched on an unpiloted test flight. In the campaign leading up to launch, engineers ran into a variety of problems ranging from fuel leaks to unexpected propellant flow behavior in the launch pad’s plumbing. Launch was delayed for months while engineers worked to resolve the problems.

For the rocket’s second launch, multiple upgrades and improvements were implemented and Blackwell-Thompson said she was optimistic the fueling test would go well.

“Why do we think that we’ll be successful? It’s the lessons that we learned,” she said last week.

“Artemis I was the test flight, and we learned a lot during that campaign, getting to launch,” she said. “And the things that we learned relative to how to go load this vehicle, how to load LOX (liquid oxygen), how to load hydrogen, have all been rolled in to the way in which we intend to load the Artemis II vehicle.”

But the countdown still ran into problems with hydrogen leakage. NASA managers planned to brief reporters on the results of the fueling test Tuesday.