A plumbing issue in a rocket engine has forced a postponement of the first launch of NASA’s most powerful rocket on a historic flight around the Moon.
NASA’s Space Launch System rocket is well into the fueling process for today’s launch of the uncrewed Artemis 1 mission, which is intended to test all the systems that will be put into operation during crewed missions to the Moon.
During the countdown, engineers detected a problem with one of the main stage’s four RS-25 rocket engines. The rocket is designed to “bleed off” some of its supercooled propellant to prepare its engines – basically, to keep the engines at the right temperature for launch. But the hydrogen purge process was not working properly for the No. 3 engine.
Engineers tried various techniques to free the plumbing obstruction, and NASA called an unscheduled hold at T-minus-40 minutes to give them more time to find a solution. But ultimately, mission managers decided to clear 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 wait to decide what the plan is to move forward to fix the engine bleed and then go from there,” traffic commentator Derrol Nail said.
During the early stages of the fueling process, the launch team had to resolve an issue involving a hydrogen leak. Another issue involved what appeared to be a crack in the foam insulation covering the rocket. Engineers eventually determined that the fissure, and puffs of icy air coming from the fissure, were similar to those seen during the shuttle countdown. NASA said this particular phenomenon would not be a show-stopper.
It’s not uncommon for such malfunctions to occur during preparations for a rocket’s first launch—and the Space Launch System is arguably the most complex and expensive rocket that NASA and its commercial partners (led by Boeing) have developed since the program space shuttle. Problems with the power system occurred during dress rehearsals held in recent months.
“We don’t launch until it’s right,” NASA Administrator Bill Nelson said after today’s scrub. “It just goes to show that this is a very complex machine, a very complex system, and it all has to work. And you don’t want to light the candle until it’s ready.”
Nelson noted that his own space shuttle launch, which took place in 1986 while he was a member of Congress, encountered four crashes. “If we had started in any of these scrubs, it wouldn’t have been a good day,” he said.
Artemis 1’s mission plan calls for the SLS rocket, which is 15 percent more powerful than the Apollo-era Saturn V rocket, to place an uncrewed Orion capsule on a 42-day journey that spans up to 40,000 miles beyond moon. Orion would go into a circular lunar orbit and then return to a dip in the Pacific Ocean. One of the key tests would come when Orion’s heat shield encounters temperatures that rise to nearly 5,000 degrees Fahrenheit during atmospheric reentry.
Three sensor mannequins inside the Orion capsule will collect data on environmental conditions, including radiation exposure, during the journey.
NASA also plans to test an Alexa-style voice assistant developed by Amazon in partnership 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 headed for the moon or Mars.
Data collected during the Artemis 1 mission will help NASA prepare for Artemis 2, which aims to send a crew of astronauts around the Moon in the 2024 timeframe, and for Artemis 3, which aims to put astronauts on the lunar surface in 2025 or 2026. This would be the first manned lunar landing since Apollo 17 in 1972.
Update for 11:20 am. PT August 29: Artemis mission manager Mike Sarafin said his team will need at least a day to address the hydrogen bleed problem as well as other issues that arose during the countdown. The plan is to look at the cooling systems for the No. 3 engine as well as the other three SLS core stage engines.
Plans for the next launch attempt will not be announced until Tuesday at the earliest.
In addition to the problem with the venting process, engineers had to deal with a leaking vent valve in the intermediate tank section of the SLS core, Sarafin said. He also noted that the weather would be “prohibitive” at the start of today’s two-hour launch window due to precipitation, and that the threat of lightning would have created prohibitive conditions during later phases of the window.
Vice President Kamala Harris attended the countdown proceedings, and although she wasn’t able to see the 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 preparations for the launch gave him a new appreciation for what members of the Apollo team accomplished more than half a century ago.
“They didn’t know it could be done, which is even more impressive,” Free told reporters. “We’ve seen it happen. We’re testing it on a new vehicle, so it’s really impressive to me to think they didn’t even know it could be done. You don’t know how hard it is because of what’s in front of you.”