NASA chooses to fix Megarocket hydrogen leak on launch pad

NASA is preparing to replace a faulty seal linked to a hydrogen leak that led to SLS’s second launch attempt on Saturday. Repairs will take place on the launch pad, which is ideal from a testing perspective, but NASA still needs to get the giant rocket back to the assembly building to meet safety requirements.

Technicians will replace a seal on the quick disconnect, an interface that connects the mobile launcher’s liquid hydrogen fuel line to the core stage of the Space Launch System, according to a brief statement from NASA statement. Teams will also check plate coatings on other umbilicals to rule out hydrogen leaks at these locations. “With seven main umbilical lines, each line can have multiple connection points,” NASA explained.

NASA is attempting an uncrewed mission to the moon and back, with a view to a human lunar landing later this decade. But Dhe first steps of the launch attempt On September 3, an inadvertent command briefly increased pressure in the system, possibly damaging some components. A leak of unmanageable hydrogen caused the to rub— the second in a week. The earlier scrub on Monday August 29 was also marred by a hydrogen leak, although engineers were able to fix it. In the end it was a faulty sensor which condemned the first launch attempt.

The unflown SLS rocket remains in a safe configuration, upright on Launch Pad 39B at Kennedy Space Center in Florida. NASA is looking to launch the Mission Artemis 1in which the rocket will send an uncrewed Orion spacecraft on a journey around the moon and back. The first launch period, which ran from August 23 to September 6, has come to an end, forcing a break in the action. The space agency must now prepare the 322-foot-tall (98-meter) rocket for the third launch attempt of Artemis 1, the date of which has not yet been announced.

Technicians plan to set up a temporary enclosure around the base of the rocket to protect the hardware from Florida weather. The advantage of working directly on the pad is that engineers will be able to test the patch under cryogenic conditions. During launch preparations, liquid hydrogen is pumped through the system at ultra-cold temperatures reaching -423 degrees Fahrenheit (-253 degrees Celsius). This, together with the added high pressure, has the effect of contracting and deforming the components, which can lead to unwanted and dangerous leaks, especially around seals.

As a propellant, hydrogen is effective but notoriously difficult to control. Hydrogen leaks were an all-too-common source of scrubs in the days of the Space Shuttle, and now SLS, which is also powered by a mixture of liquid hydrogen and liquid oxygenseems to suffer from the same technical difficulties.

The engineers thought return SLS to nearby Vehicle Assembly Building (VAB) for required repairs but chose to work on the pad instead. The VAB would have presented a more controlled working environment, but without the ability to reproduce the cryogenic conditions desired for testing (tests inside the VAB must be run at ambient temperatures). “Performing work on the pad also allows teams to collect as much data as possible to understand the cause of the problem,” NASA added.

SLS will probably have to revert to VAB, hotfix or not. The Eastern Range, a branch of the US Space Force, requires periodic certification of the rocket’s flight termination system. NASA has already received a waiver extending the certification from 20 to 25 days, but it is unclear whether the space agency will seek a second waiver, which would be irregular. The Eastern Channel oversees launches from Kennedy Space Center and Cape Canaveral Space Force Station, and works to ensure public safety.

During a press briefing on Saturday, Mike Sarafin, Artemis mission manager, said “it’s not our decision, it’s the Range’s decision”. He added that a Range waiver could keep the rocket on the pad, “but that’s not likely.” So under the eastern range restrictions, and until we hear otherwise from NASA about a second waiver, the rocket to have to return to the VAB before the next launch period.

A third launch attempt in late September or early October remains a remote possibility. The next period opens on September 19 and ends on October 4, with no possibility of launching on September 29 and 30. For this to work, however, NASA would need to complete its latest patch, run tests, send SLS back to VAB for recertification (which involves a very short confidence test), and then bring it back to the launch pad. It’s possible, but ground crews will have to make it happen.

Otherwise, the third launch period opens on October 17 and ends on October 31, with launch exclusions on October 24, 25, 26 and 28. Two other periods, one in November and one in December, exist during the current calendar year.

There is still plenty of time for SLS to launch in 2022, but it all depends on how quickly engineers can master this complex system. SLS is the most powerful rocket ever built by NASA and is a key part of the space agency Artemis programwhich aims for a sustained and prolonged human presence on and around the Moon.

After: What to know about Lunar Gateway, NASA’s future lunar-orbiting space station.