After working around a hydrogen leak, NASA pressed ahead with a “wet dress” rehearsal countdown of its Artemis II moon rocket Monday, loading the huge rocket with more than 750,000 gallons of liquid oxygen and hydrogen fuel, only to be derailed by additional leakage early Tuesday.
Already running several hours behind schedule, the countdown resumed at the T-minus 10-minute mark around 12:09 a.m. EST Tuesday, ticking down toward a simulated engine start.
But four-and-a-half minutes later, the countdown stopped again due to a “liquid hydrogen leak at the interface of the tail service mast umbilical, which had experienced high concentrations of liquid hydrogen earlier in the countdown,” NASA said on social media.
The Space Launch System rocket’s mobile launch platform is equipped with two tail service masts, large side-by-side structures at the base of rocket that house propellant lines leading to pull-away umbilical assemblies on a side of the booster’s engine compartment.
“The launch control team is working to ensure the SLS rocket is in a safe configuration and (to) begin draining its tanks,” NASA said.
The agency said in a blog post early Tuesday that, “To allow teams to review data and conduct a second wet dress rehearsal, NASA now will target March as the earliest possible launch opportunity for the flight test.”
“Moving off a February launch window also means the Artemis II astronauts will be released from quarantine, which they entered in Houston on Jan. 21. As a result, they will not travel to NASA’s Kennedy Space Center in Florida Tuesday as tentatively planned. Crew will enter quarantine again about two weeks out from the next targeted launch opportunity,” NASA added.
The agency only had three days — Feb. 8, 10 and 11 — to propel four astronauts on a flight to the moon this month.
Hydrogen leaks have proven extremely difficult to repair at the launch pad, and a Super Bowl Sunday launch appears unlikely unless managers conclude the leak is manageable as is. But no final decisions on a path forward are expected until engineers have a chance to review the data. A news briefing is expected at 1 p.m. Tuesday.
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 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 percent full, a leak was detected at an umbilical plate where a fuel line from the launch pad is connected to the base of the SLS rocket’s first stage. After a brief pause, engineers resumed fuel flow but again cut it off with the tank about 77 percent 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. “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. EST, but the test ran longer than originally planned. As of 9:55 p.m., the countdown was in an extended hold at the T-minus 10-minute mark. The count finally resumed just after midnight, only to be stopped a final time at T-minus five minutes and 15 seconds.
NASA
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 Tuesday to begin final preparations, but that will depend 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.”
Most of the fixes and upgrades appeared to work as planned. But leakage at the tail service mast umbilical, a problem during the first Artemis flight in 2022, cropped up again the second time around.
