NASA's star-crossed Space Launch System moon rocket was grounded for the second time in five days Saturday, this time by a large hydrogen leak in a fuel line quick-disconnect fitting that will delay the $4.1 billion booster's maiden flight by several weeks, likely into October.
The latest delay was a frustrating disappointment to the Kennedy Space Center work force, invited guests and thousands of area residents and tourists who lined area roads and beaches to watch NASA's most powerful rocket blast off, raising the curtain on the agency's Artemis moon program.
But faced with a large hydrogen leak and without enough time to make repairs before the current lunar launch period ends Tuesday, NASA managers had little choice but to order a delay for thetest flight.
Engineers are assessing two options to fix the latest problem: replace components in the suspect fitting at the launch pad and carry out a mini fueling test with liquid hydrogen to verify leak-free performance. Or roll the rocket back to the Vehicle Assembly Building and carry out repairs there.
While the VAB would provide shelter from the weather and would not require assembly of an environment enclosure to protect sensitive components during the repair work, engineers would not be able to test the fitting with cryogenic hydrogen. And that's when leaks are most likely to show up.
Either option means a multi-week launch delay. The next lunar launch period starts Sept. 19 and runs through Oct. 4. But NASA is scheduled to launch a fresh crew to the International Space Station aboard a SpaceX capsule on Oct. 3 and the agency wants to avoid a conflict.
That means the SLS launch likely will slip into the next launch period, which opens Oct. 17 and runs through Halloween, unless a solution can be found to speed up the repair work.
"This is an incredibly hard business," said Artemis 1 mission manager Mike Sarafin. "Our focus is on understanding the problem. ... We'll follow up next week when we have those options flushed out further."
During Saturday's countdown, engineers made three attempts to properly "seat" a suspect seal in the 8-inch quick-disconnect fitting, but none of them worked. After a "no-go" recommendation from the engineers working the problem, Launch Director Charlie Blackwell-Thompson called off the countdown at 11:17 a.m. EDT.
"We'll go when it's ready," said NASA Administrator Bill Nelson. "We don't go until then, especially now, on a test flight."
It's not yet clear what caused the leak, but Sarafin said a valve was inadvertently cycled during the initial moments of the fuel loading operation, briefly over pressurizing the lines and the quick-disconnect fitting.
"There was an inadvertent pressurization of the hydrogen transfer line that exceeded what we had planned, which was about 20 pounds per square inch," he said. "It got up to about 60 pounds per square inch. The flight hardware itself, we know it is fine, we did not exceed the maximum design pressure.
"But there's a chance that the soft goods, or the seal in the eight-inch quick disconnect saw some effects from that, but it's too early to tell. ... What we do know is that we saw a large leak."
The goal of the Artemis 1 mission is to boost an unpiloted Orion capsule into a distant orbit around the moon, testing the spacecraft in the deep space environment before returning it to Earth for a high-speed, high-temperature re-entry.
If the initial uncrewed test flight goes well, NASA plans to launch four astronauts on an around-the-moon shakedown flight — Artemis 2 — in 2024 and to land the first woman and next man near the moon's south pole the 2025-26 timeframe. But all of that hinges on a successful Artemis 1 test flight.
The long-awaited mission must take off during specific launch periods based on the constantly changing positions of the Earth and moon, the desired lunar orbit for the Orion spacecraft and the power of the SLS rocket to put it on the proper trajectory.
Complicating the planning, flight planners want to avoid putting the solar-powered spacecraft in the moon's shadow for extended periods and they want to ensure a daylight splashdown.
The current launch window closes Tuesday, the same day certification of batteries in the rocket's self-destruct system expires. That alone would have required roll back to the Vehicle Assembly Building for already-planned servicing because the batteries cannot be accessed at the launch pad.
after four countdown rehearsals and fueling tests, all of which ran into multiple technical snags, including hydrogen leaks in different systems.
During Monday's launch attempt, a faulty temperature sensor led to uncertainty as to whether the SLS rocket's four RS-25 first stage engines were receiving the proper pre-launch cooling.
In addition, the same fitting that leaked Saturday also leaked during the Monday launch try, but concentrations were much lower and engineers managed get the hydrogen tank filed before the enging cooling issue cropped up.
As it turned out, the engines were, in fact, being properly chilled and a faulty temperature sensor was responsible for misleading engineers.
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