NASA deals with hydrogen leak, fuels Artemis moon rocket in critical test

NASA deals with hydrogen leak, fuels Artemis moon rocket in critical test

NASA’s leaky Space Launch System moon rocket first ran into worrisome problems during a fueling test on Wednesday, but engineers “managed” a fresh leak in its kit. test launch on 3 September and they were able to fill the massive booster with a total load of 750,000 gallons of supercooled propellant.

They also performed two other critical tests, verifying their ability to properly cool the rocket’s four hydrogen fuel engines as required for flight and successfully pushing the core stage hydrogen tank to flight levels.

Launch Director Charlie Blackwell-Thompson would not speculate on whether NASA might push forward toward the September 27 launch date as discussed earlier, saying she wanted her team to review the details of the test. before drawing any conclusions. But she said she was “extremely motivated by the test today”.

NASA's Space Launch System mega rocket tops pad 39B at the Kennedy Space Center on Wednesday.  Engineers conducted a full-scale fueling test to verify repairs to fix a hydrogen leak that ended a launch attempt on September 3, but another leak appeared in the same system.  This time around, engineers were able to use different flow rates and pressures to fully fuel the giant rocket.  / Credit: NASA

NASA’s Space Launch System mega rocket tops pad 39B at the Kennedy Space Center on Wednesday. Engineers conducted a full-scale fueling test to verify repairs to fix a hydrogen leak that ended a launch attempt on September 3, but another leak appeared in the same system. This time around, engineers were able to use different flow rates and pressures to fully fuel the giant rocket. / Credit: NASA

“I don’t like to get ahead of the details, so I want the team to have the opportunity to look at it to see if there are changes we need to make to our loading procedures, our timelines or we’re good as it is,” she said.

The discussion could be challenging since the seal blamed for the launch delay was changed earlier and the same system leaked, at least initially, again on Wednesday.

But even if the team determines that September 27 is a viable target for the rocket’s maiden flight, it may not be enough. The Space Force Eastern Range, which oversees all military and civilian launches from Florida, did not rule on NASA’s request to waive a requirement to inspect batteries in the rocket’s self-destruct system.

The batteries cannot be accessed at the launch pad and without a waiver, NASA will have to tow the 332-foot-tall SLS rocket back to Kennedy Space Center’s iconic Vehicle Assembly Building, delaying the launch for a month or bigger.

The long-awaited Artemis 1 mission is designed to send an unpiloted Orion crew capsule on a 40-day trip around the moon and back to pave the way for the first piloted Artemis mission in 2024. If successful, it NASA plans to land two. astronauts near the moon’s south pole in the 2025-26 timeframe, the first in a sustained series of missions.

But engineers have been plagued by unacceptable hydrogen leaks and other issues during the rocket’s launch. Years behind schedule and billions over budget, the SLS rocket first pulled out to launch pad 39B on March 17 for a fueling test to clear the launch path. But back-to-back scrubs were ordered on April 3 and 4 due to multiple unrelated problems.

Liquid oxygen and hydrogen propellants flow into the massive core of the Space Launch System through 8-inch-wide retractable lines that run from two tail service tree umbilicals (left) to the fittings attached to the side of the booster.  There were initial problems with a leak in the hydrogen fitting during Wednesday's fueling test, but engineers were able to replace a suspected seal and successfully load the rocket with propellants.  / Credit: NASA

Liquid oxygen and hydrogen propellants flow into the massive core of the Space Launch System through 8-inch-wide retractable lines that run from two tail service tree umbilicals (left) to the fittings attached to the side of the booster. There were initial problems with a leak in the hydrogen fitting during Wednesday’s fueling test, but engineers were able to replace a suspected seal and successfully load the rocket with propellants. / Credit: NASA

The third test was canceled on April 14 due to a hydrogen leak near the core stage fuel fast line disconnect, and the rocket was rolled back to the VAB for servicing. It returned to the launch pad in early June only to suffer more problems during a June 20 fueling test, when engineers were unable to cool the rocket’s engines due to a stuck valve in another system.

The rocket was returned to the VAB for repairs in early July and was towed back to the pad in mid-August for what NASA hoped would be its maiden flight. But a launch attempt was aborted on August 29 due to more hydrogen issues and again on September 3 when the 8-inch quick-disconnect fitting leaked.

After the second launch scrub, NASA managers chose to disassemble the suit at the launch pad, replace an internal seal, reassemble the hardware and perform a fueling test to verify the seal’s integrity. Hydrogen leaks usually only show up when the plumbing is exposed to cryogenic temperatures — minus 423 degrees Fahrenheit in this case,

Oxygen vapor escapes from vents on the side of the Space Launch System rocket as propellants are loaded into the upper stage of the booster.  / Credit: NASA

Oxygen vapor escapes from vents on the side of the Space Launch System rocket as propellants are loaded into the upper stage of the booster. / Credit: NASA

Repair work was completed last week and testing began normally enough on Wednesday, with oxygen and hydrogen flowing into separate core stage tanks at low rates. In an effort to mitigate the thermal shock when switching to “fast net” mode, the loading sequence was slowed down and flow rates were reduced to ease stresses on the hardware.

But when the flow rate and pressure increased, sensors detected an immediate increase in hydrogen gas in a containment housing around the just-repaired quick-disconnect fitting, indicating a leak. Sensors found concentrations of up to 7%, well above the safety limit of 4%.

The engineers then chose to heat the fittings before resuming the hydrogen flow in the hope of forcing the internal seal to “reset” itself. When the flow started again, leakage was still present, but it was well below the 4% threshold and the engineers were able to press on, eventually at the top of the hydrogen tank with a total load of 730,000 gallons.

A close examination of the sensor data revealed that the leakage rate decreased as the pressure increased, reversing the behavior initially observed. That’s how the device is designed to work, suggesting that efforts to reposition the seal were at least partially successful.

With the core stage’s hydrogen and oxygen tanks full, engineers pressed ahead with the loading of the SLS rocket’s upper stage while simultaneously conducting the pressurization and engine cooling tests.

Another hydrogen leak was reported near a 4-inch quick-disconnect fitting used for the cooling test. Although engineers have already agreed to proceed with the observed concentration, it would stop the actual launch countdown. No word yet on the impact, if any, that issue may have on launch planning.

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