NASA’s leak-plagued Space Launch System moon rocket initially encountered worrisome problems during a tank test on Wednesday, but engineers “managed” a new leak in a fitting thatand were able to fill the massive booster with a full load of 750,000 gallons of super-cold propellants.
They also conducted two other critical tests, verifying their ability to properly cool the rocket’s four hydrogen-powered engines as required for flight, and successfully bring the nuclear-stage hydrogen tank up to flight level.
Launch Director Charlie Blackwell-Thompson wouldn’t speculate on whether NASA would move forward to a September 27 launch date, as discussed earlier, and said she wanted her team to review the data from the test before jumping to conclusions. But she said she was “extremely encouraged by today’s test.”
“I don’t like to get ahead of the data, so I’d like the team to have a chance to look at it to see if there are any changes we need to make to our loading procedures, our timelines or whether we’re going to have to make any changes.” it’s fine the way it is,” she said.
The discussion could be challenging, as the seal responsible for the earlier launch delay was replaced and the same system, at least initially, leaked again on Wednesday.
But even if the team concludes Sept. 27 is a viable target for the missile’s maiden flight, it may not be enough. The Space Force Eastern Range, which oversees all military and civilian launches from Florida, has yet to comment on a request from NASA to waive the requirement to inspect batteries in the missile’s self-destruct system.
The batteries will not be accessible on the launch pad, and without a waiver, NASA will be forced to tow the 332-foot-tall SLS rocket back to the Kennedy Space Center’s iconic Vehicle Assembly Building, delaying the launch for a month or more.
The highly anticipated Artemis 1 mission is designed to send an unmanned Orion crew pod on a 40-day voyage around the moon and back to clear the way for the first piloted Artemis mission in 2024. If all goes well, NASA plans to send two astronauts near the moon’s south pole in the time frame of 2025-26, the first in an ongoing series of missions.
But engineers are inundated with elusive hydrogen leaks and other problems leading up to the rocket’s launch. Years behind schedule and billions over budget, the SLS rocket was pulled to launch pad 39B for the first time on March 17 for a fuel test to clear the way for launch. But back-to-back scrubs were ordered on April 3 and 4 due to multiple unrelated issues.
A third test on April 14 was called off due to a hydrogen leak near the nuclear-stage fuel line shortcut, and the missile was rolled back to the VAB for maintenance. It returned to the launch pad in early June, but ran into more trouble during a tank test on June 20, 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 returned to the path in mid-August for what NASA hoped would be its maiden flight. But a launch attempt on Aug. 29 was called off due to more hydrogen problems and again on Sept. 3 when the 8-inch quick coupler leaked.
In the wake of the second launch scrub, NASA executives chose to take apart the fitting on the launch pad, replace an internal seal, reassemble the hardware, and run a fuel test to verify seal integrity. . Hydrogen leaks usually only appear when the plumbing is exposed to cryogenic temperature – in this case minus 423 degrees Fahrenheit,
The repair work was completed last week and the test started normally enough Wednesday, with oxygen and hydrogen flowing into the core phase at low speed in separate tanks. In an effort to reduce thermal shock when switching to “quick fill” mode, the charging sequence was slowed down and flow rates decreased to reduce stress on the hardware.
But as flow and pressure increased, sensors detected an immediate buildup of gaseous hydrogen in a containment housing around the newly repaired quick-connection, suggesting a leak. Sensors detected concentrations up to 7%, well above the safety limit of 4%.
Engineers then chose to warm up the fittings before restarting the hydrogen flow in hopes of coaxing the internal seal to “replace” itself. When power was restored, there was still a leak, but it was well below the 4% threshold and the engineers were able to push through, eventually filling the hydrogen tank with a full 730,000 gallon load.
A close examination of sensor data showed that with a reversal of the initially observed behavior, the leak rate decreased as the pressure increased. That’s how the fitting is designed to work, suggesting that attempts to reseat the seal were at least partially successful.
With the hydrogen and oxygen tanks in the core stage full, the engineers continued to load the top stage of the SLS rocket while conducting the pressurization and engine cooling tests.
Another hydrogen leak was reported near a 4-inch quick disconnect used for the cooling test. While engineers had already agreed to continue with the observed concentration, this would have halted an actual launch. No word yet on the potential impact of that issue on the launch schedule.