Gizmodo By George Dvorsky
A hydrogen leak prevented the launch of NASA’s SLS rocket this Saturday, in what is a troubling yet highly predictable development.
NASA’s Space Launch System is powered by a mixture of liquid hydrogen and liquid oxygen. Together, these elements provide for a compact and extremely powerful rocket propellant, but these same attributes are also what make this fuel a liability.
The second launch attempt of SLS had to be called off on Saturday, September 3, after engineers failed to resolve a hydrogen leak in a quick disconnect—an 8-inch inlet that connects the liquid hydrogen fuel line to the rocket’s core stage. As a result of the setback, SLS probably won’t launch until October at the earliest. The Artemis 1 mission, in which an uncrewed Orion spacecraft will journey to the Moon and back, will have to wait.
Ground teams were able to fix a hydrogen leak during the first failed launch attempt on Monday, August 29, but the launch was eventually called off after a faulty sensor erroneously indicated that an engine hadn’t reached the required ultra-cold temperature. The leak on Saturday proved to be much more difficult to contain, with engineers attempting three fixes, none of which worked. “This was not a manageable leak,” Mike Sarafin, Artemis mission manager, told reporters after the scrub.
NASA is still evaluating its next steps, but the rocket must return to the Vehicle Assembly Building to undergo a mandated safety check related to its flight termination system. The rocket may require some hardware fixes on account of an inadvertent command that briefly raised the pressure within the system. The unintended over-pressurization may have contributed to the leaky seal, and it’s something engineers are currently evaluating as a possibility.
Inheriting the hydrogen problemHydrogen leaks are nothing new for NASA. Scrubs of Space Shuttle launches happened with upsetting regularity and were often the result of hydrogen leaks. One of the more infamous episodes was “the summer of hydrogen,” when ground teams spent more than six months trying to locate an elusive hydrogen leak that grounded the Shuttle fleet in 1990. SLS is heavily modeled after the Space Shuttle, including the use of liquid hydrogen propellant, so hydrogen-related scrubs could certainly have been predicted. But SLS is what it is, and NASA has little choice but to manage this limitation of its mega Moon rocket.
Jordan Bimm, a space historian at the University of Chicago, says NASA continues to use liquid hydrogen for political rather than technical reasons.
“Since the creation of NASA in 1958, the agency has used contractors located around the U.S. as a way to maintain broad political support and funding for space exploration in Congress,” Bimm told me. “The first system to use liquid hydrogen was the Centaur rocket developed in the 1950s and 1960s. In 2010, the U.S. Congress, in their authorization act funding NASA, mandated that the Agency use existing technologies from the Shuttle in their next-generation launch system.” To which he added: “This was a political decision meant to maintain contractor jobs in key political districts and from that funding and support in Congress for NASA.”
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https://gizmodo.com/nasa-hydrogen-leaks-sls-rocket-space-shuttle-1849500702
