The leak that delayed NASA’s latest attempt to blast off its moon rocket over the weekend was tied to the agency’s use of liquid hydrogen, a fuel some space companies have chosen not to use as they develop new engines for their own large rockets.
Hydrogen is light and burns extremely hot, making it an efficient propellant to use on different stages of a rocket launch, the National Aeronautics and Space Administration has said.
But hydrogen is also incredibly tiny, and has a tendency to escape efforts to easily contain it, engineers have said.
That is what happened Saturday, when NASA tried for the second time last week to launch the Artemis I mission, using the Space Launch System rocket to blast a spacecraft to a lunar orbit. Earlier, on Aug. 29, NASA was able to fill up the liquid-hydrogen tank on the rocket, but engineers called off that launch attempt largely because of another issue.
The benefits and difficulties of liquid hydrogen as a propellant for rocket launches are well known to engineers at NASA.
NASA officials said Saturday that engineers will now try to dig into why a relatively large leak emerged that day. Officials have pointed to at least one mistake, involving too much pressure during a chilling procedure that occurred during prelaunch operations on Saturday, but said it was too soon to say that it caused the leak.
Mike Sarafin, the mission manager for Artemis, NASA’s moon-exploration effort, said that at one point on Saturday, there was an “inadvertent pressurization” on a transfer line for liquid hydrogen. The pressure was around three times the level the agency had planned, potentially affecting a seal. The sequence where the problem occurred was handled manually, according to Mr. Sarafin.
“It’s too early to tell exactly whether that was the cause” of the hydrogen leak, he said.
Many in the space industry, including former NASA officials, were still trying to understand the challenges that emerged with the rocket.
Engines for large rockets under development by some space companies don’t rely on liquid hydrogen, in combination with liquid oxygen, to power them.
SpaceX switched from using that propellant to liquid methane as the company was designing its Raptor engines, Mr. Musk said on Twitter on Saturday night. SpaceX plans to use dozens of Raptor engines on Starship, the two-part rocket system it has been developing but hasn’t tried to blast to orbit yet.
Methane offers the “best combo of high efficiency & ease of operation,” he said in a tweet, adding that methane tanks are smaller and don’t need insulation.
SpaceX aims to use Starship for deep-space operations, and NASA hired SpaceX to provide a Starship lander to transport astronauts to the surface of the moon on a future NASA Artemis mission.
A spokesman for Space Exploration Technologies Corp., the formal name for SpaceX, didn’t respond to a request for comment.
Blue Origin LLC,
space company, uses liquid hydrogen on the engines on its New Shepard rocket, which conducts suborbital space flights, but it is taking a different approach for the engines that would power its New Glenn rocket, which hasn’t flown yet.
Those engines, called BE-4s, use a form of liquid methane. Blue Origin didn’t respond to a request for comment.
Bill Nelson, NASA’s administrator, said the postponement Saturday and the first one on Aug. 29 were the right decisions as engineers worked to launch a complex rocket for the first time.
He also defended the SLS rocket’s use of liquid-hydrogen fuel. As a senator representing Florida, Mr. Nelson helped pass legislation in 2010 that directed NASA to develop the SLS rocket program.
That bill included language calling on the agency to use assets from the shuttle program and other agency efforts, including liquid-fuel engines. The space shuttles were powered by engines using liquid hydrogen, as well as liquid oxygen, and the four engines on the SLS were previously used on shuttle flights.
“We did not have any question about hydrogen,” he said at a briefing Saturday, discussing that legislation.
Congress has been supportive of the SLS program, providing more funding for it over the last 10 fiscal years than NASA asked for, according to a recent analysis from the Planetary Society, a group that advocates for space exploration. It wasn’t immediately clear if NASA’s failure to launch the SLS so far would affect how Congress views the agency’s efforts.
Launch teams tried three times Saturday to stop the leak that emerged on a line that flows liquid hydrogen into a tank on the SLS rocket it was preparing to launch toward the moon, agency officials said over the weekend.
During the Aug. 29 launch try, engineers dealt with a smaller hydrogen leak that they were able to troubleshoot. After a problem with an engine-cooling procedure, however, the agency called off the first attempt.
NASA has faced problems with liquid-hydrogen fuel before.
In 1990, crews at the Kennedy Space Center struggled with a hydrogen leak that grounded the agency’s shuttle fleet during what was dubbed “the summer of hydrogen,” according to a NASA article about the episode published more than a decade ago.
The agency, meanwhile, revamped what is called the Launch Equipment Test Facility at the Kennedy property to support SLS rockets, a description on a Kennedy website said. That facility’s capabilities include creating liquid-hydrogen flows for test runs.
The Artemis I mission is designed as an uncrewed test of the agency’s SLS rocket and the Orion spacecraft that sits on top of it. The massive rocket would blast Orion toward a lunar orbit, and then the ship would travel back to Earth, testing the heat shield on its crew capsule during re-entry.
The operation is a precursor to a flight with astronauts on Orion planned for 2024. A year later, NASA hopes to return astronauts to the lunar surface.
Write to Micah Maidenberg at [email protected]
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