A plumbing issue on a rocket engine has forced a postponement in the first launch of NASA’s most powerful rocket on a history-making round-the-moon flight.
NASA’s Space Launch System rocket went far into the fueling process for today’s start of the uncrewed Artemis 1 mission, which is meant to test all the systems that will come into play during crewed missions to the moon.
During the countdown, engineers detected a problem with one of the core stage’s four RS-25 rocket engines. The rocket is designed to “bleed off” some of its supercooled propellant to condition its engines — basically, to maintain the engines at the proper temperature for startup. But the hydrogen bleed procedure wasn’t working properly for engine No. 3.
Engineers tried various techniques to free up the plumbing snag, and NASA called an unplanned hold at T-minus-40 minutes to give them more time to come up with a fix. But in the end, mission managers decided to scrub the launch for today.
The next launch opportunity comes on Friday, when a two-hour window opens at 12:48 p.m. ET (9:48 a.m. PT). “However, we will await a determination of what the plan is to go forward to remedy the engine bleed, and then go from there,” said launch commentator Derrol Nail.
During the early phases of the fueling process, the launch team had to resolve an issue involving a hydrogen leak. Another issue involved what appeared to be a fissure in the foam insulation covering the rocket. Engineers eventually determined that the fissure, and the puffs of chilled air that emanated from the fissure, were similar to what had been observed during space shuttle countdowns. NASA said that particular phenomenon wouldn’t be a show-stopper.
It’s not uncommon for such glitches to surface during preparations for the first launch of a rocket — and the Space Launch System is arguably the most complex and costliest rocket NASA and its commercial partners (led by Boeing) have developed since the space shuttle program. Problems with the fueling system cropped up during dress rehearsals that were conducted over the past few months.
“We don’t launch until it’s right,” NASA Administrator Bill Nelson said after today’s scrub. “It’s just illustrative that this is a very complicated machine, a very complicated system, and all those things have to work. And you don’t want to light the candle until it’s ready to go.”
Nelson noted that his own space shuttle launch, which took place in 1986 while he was a member of Congress, encountered four scrubs. “Had we launched on any one of those scrubs, it wouldn’t have been a good day,” he said.
Artemis 1’s mission plan calls for the SLS rocket, which is 15% more powerful than the Apollo era’s Saturn V rocket, to loft an uncrewed Orion capsule on a 42-day trip that ranges out as far as 40,000 miles beyond the moon. Orion would go into a looping lunar orbit, and then return to a Pacific Ocean splashdown. One of the key tests would come when Orion’s heat shield encounters temperatures rising to nearly 5,000 degrees Fahrenheit during atmospheric re-entry.
Three sensor-laden mannequins inside the Orion capsule would collect data about environmental conditions, including radiation exposure, during the trip.
NASA also plans to test an Alexa-style voice assistant that was developed by Amazon in collaboration with Cisco and Lockheed Martin. The voice-enabled AI system on Orion, nicknamed Callisto, could provide real-time information and companionship to future space crews heading for the moon or Mars.
Data gathered during the Artemis 1 mission would help NASA prepare for Artemis 2, which aims to send a crew of astronauts around the moon in the 2024 time frame; and for Artemis 3, which aims to put astronauts on the lunar surface in 2025 or 2026. That would be the first crewed lunar landing since Apollo 17 in 1972.
Update for 11:20 a.m. PT Aug. 29: Artemis mission manager Mike Sarafin said his team will take at least a day to troubleshoot the hydrogen bleed problem as well as other issues that arose during the countdown. The plan is to look at the cool-down systems for engine No. 3 as well as for the SLS core stage’s other three engines.
Plans for the next launch attempt won’t be announced until Tuesday at the earliest.
In addition to the problem with the bleed procedure, engineers had to deal with a leaking vent valve in the SLS core stage’s intertank section, Sarafin said. He also noted that the weather would have been “no-go” at the beginning of today’s two-hour launch window due to precipitation, and that the threat of lightning would have posed no-go conditions during later phases of the window.
Vice President Kamala Harris attended the countdown proceedings, and although she wasn’t able to see a launch, Nelson said she had a “very productive visit.” After the scrub, Harris tweeted her support for the Artemis moon program:
Jim Free, NASA’s associate administrator for exploration systems development, said the preparations for launch gave him a new appreciation for what members of the Apollo team accomplished more than a half-century ago.
“They didn’t know it could be done, which is even more impressive,” Free told reporters. “We’ve seen it done. We’re trying this with a new vehicle, so it’s really impressive to me to think that they didn’t even know that it could be done. You don’t know how hard it is because of what’s laid out in front of you.”