NASA Ready for “Kinder, Gentler” Artemis I Tanking Test

NASA Ready for “Kinder, Gentler” Artemis I Tanking Test

NASA said today it is ready to conduct a tanking test of the Artemis I Space Launch System rocket on Wednesday. A main purpose of the test is to see if fixes made to repair a hydrogen leak during an attempted launch on September 3 solved the problem. They will proceed in a “kinder, gentler” manner this time. If the test goes well, NASA is targeting September 27 to try the launch again, but it also needs a waiver from the Space Force to launch without replacing a critical battery for the Flight Termination System. That answer is not expected until after the test.

Artemis I is an uncrewed test flight of the Space Launch System and Orion spacecraft. The first attempt to launch on August 29 was scrubbed when a faulty sensor indicated one of the four engines was not chilled sufficiently. NASA tried again on September 3, but called it off because of a hydrogen leak at a Quick Disconnect (QD) fitting between the rocket and the Mobile Launcher.

SLS uses cryogenic liquid hydrogen and liquid oxygen as propellant. The propellant flows through lines on the Mobile Launcher into the tanks of the Core Stage and the Interim Cryogenic Propulsion Stage and must be topped off almost until the moment of launch because it boils off. The QDs instantly separate the lines from the rocket at liftoff.

The Space Launch System rocket and Orion spacecraft attached to the Mobile Launcher atop the Crawler-Transporter on the way to Launch Complex 39-B, June 6, 2022. The SLS core stage is orange. The white Interim Cryogenic Propulsion Stage and white Orion spacecraft are on top. There are two white Solid Rocket Boosters on each side of the Core Stage, one of which is visible. Photo credit: NASA/Ben Smegelsky.

Hydrogen leaks were a relatively common occurrence on SLS’s predecessor, the space shuttle, and were encountered during SLS tests in April and June and on August 29. But the leak on September 3 was much larger. No hydrogen is supposed to leak and detecting more than 4 percent concentration is a threshold at which fueling must stop because it is so flammable.

At a briefing today, SLS Chief Engineer John Blevins said the level reached 8 percent around the 8-inch QD for the Core Stage. When they stopped the flow and tried again the same thing happened so the launch was scrubbed.

At a post-scrub briefing that day, Artemis Mission Manager Mike Sarafin said the leak might have been caused by an “inadvertent” overpressurization of the hydrogen transfer line during a manual operation. A few days later, Mike Bolger, NASA’s Exploration Ground Systems program manager, said the management team apologized to the individual who made the error because it was a last-minute change and not enough time was provided to practice the new procedure, which ordinarily is automated.

At today’s briefing, Sarafin said a “witness mark or indentation” was found on the 8-inch QD seal. The indentation was “just under 0.01 inches” which “doesn’t sound like a lot” but “hydrogen is the smallest particle on the atomic chart.” He said the indentation was “associated with foreign object debris.”

Later, however, Jeremy Parsons, Deputy Manager of Exploration Ground Systems, said they do not know what caused the indentation. There are several potential causes and they are working to mitigate all of them. He explicitly said they have close-out photos showing there was no foreign object debris, or FOD.

“Of the potential causes, FOD is one of them. As well it could be thermal or pressure shock. What we’re doing is we’re trying to mitigate each one of those branches of the fault tree.”

Chief Engineer Blevins went further, explaining they may never know exactly what happened. What they have determined is that they need to load the fuel in a “kinder, gentler” manner to avoid pressure and thermal spikes when the super-cold propellant meets seals and other hardware.

“There’s just so many different things that could have created the indentation — and we believe the indentation is consistent with a leak, but we don’t totally know that either. …

“The discussion of FOD has come up, but as Jeremy said, there’s close-out photos to show that’s likely not part of this particular case. …

“Each one of the fault tree lines, and there are many which have to do with how we are loading the vehicle and that lends itself to the kinder, gentler process that leads to lower rates of change in pressure and temperature. ….

“I actually do not hang my hat on any particular cause on the fault tree. I think the fault tree probably includes the actual cause. I think the cause is probably not knowable in any particular discreet way because I just don’t have the information to make those conclusions. These are all plausible scenarios that are consistent with leakage and we are going down a path to eliminate those.”

The bottom line is they will only know if it’s fixed when they do the test on Wednesday.

The plan is to fill both the Core Stage and ICPS tanks with propellant — hence “tanking test” — to see if the seals hold. They will not take the countdown all the way down to “terminal count” just before launch, but will stop before the T-10 minute mark.

Tom Whitmeyer, NASA Deputy Associate Administrator for Common Exploration Systems Development, said fueling will begin at 7:00 am ET on Wednesday, the test will begin at about 1:00 pm ET, and if all goes according to plan will be over at 3:00 pm ET.

NASA TV will provide live coverage of the test with commentary on its Media Channel beginning at 7:15 am ET. Russia is launching a new crew to the International Space Station, Soyuz MS-22, at the same time with two Russian cosmonauts and NASA astronaut Frank Rubio. NASA TV’s Public Channel will switch back and forth between the test and Soyuz MS-22 operations.

An Artemis I Mission Management Team meeting is scheduled for Sunday to make a final decision on whether to proceed with launch on September 27, but Sarafin said the decision could be made earlier. They are taking everything a step at a time and “we’re gonna go when we’re ready.”

In addition to results of the test, NASA must get a waiver from the Space Force to avoid rolling the SLS back to the Vehicle Assembly Building to replace a battery in the Flight Termination System. The Space Force operates the Eastern Range and is responsible for public safety of all launches from Kennedy Space Center and the adjacent Cape Canaveral Space Force Station.  It would be in charge of activating the FTS if the rocket veered off course. The battery is certified for only 20 days. NASA already got a waiver to 25 days for the first launch attempts in late August and early September. Whether they will extend several weeks more to September 27, or the backup date of October 2, remains to be seen.

“The public safety aspect of this is not our risk to weigh,” Sarafin said. NASA officials repeatedly stress they will abide by whatever decision the Space Force makes. NASA is “respecting the Range’s process and working closely” with them.

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