Artemis I Scrubs Again

NASA’s second try to launch the Artemis I test flight around the Moon ended the same way as the first — a scrub. On Monday, several problems arose including a liquid hydrogen leak. That one was fixed, but today another hydrogen leak in a different place did not respond to the valiant efforts of NASA’s engineers. NASA officials are still investigating what went wrong, but expect it will take several weeks to fix so it will be some time before they try again.

Today the leak was in an 8-inch Quick Disconnect (QD) fitting between the rocket and the Mobile Launcher. The rocket is connected to ground systems by a number of umbilicals. QDs instantly disconnect them at the moment of launch.

In this case the QD is for the fill and drain line for liquid hydrogen (LH2) to the core stage.

Hydrogen leaks were encountered during some of the Wet Dress Rehearsals earlier this year and during Monday’s launch attempt, but they were in the tail service mast umbilical. On Monday engineers were able to re-seat that QD seal by allowing it to warm up and then chilling it again.

This QD seal did not respond to that technique even though they tried twice. They also tried pressurizing the line with nitrogen, with similar negative results.

Trying to troubleshoot the problem ate into the two-hour launch window available today and at 11:17 am ET Launch Director Charlie Blackwell-Thompson called a scrub.

During a press conference this afternoon, Artemis Mission Manager Mike Sarafin revealed that an “inadvertent pressurization of the hydrogen transfer line” had occurred. “The pressure exceeded what we had planned, which was about 20 pounds per square inch. We got up to about 60 pounds per square inch.” They are still going through the data to determine exactly what happened, but right now it appears that during a manual sequence of about a dozen commands, the wrong valve was commanded. The error was identified after 3-4 seconds and rectified.

Engineers do not think the QD hardware was damaged, but the seal (“soft goods”) might have been. A definitive connection between the overpressure event and the hydrogen leak has not been established, but it’s a possibility.  “We want to be deliberate and careful about drawing conclusions here because correlation does not equal causation,” Sarafin stressed.

NASA Administrator Bill Nelson said they will launch when they’re ready. If the vehicle has to go back to the Vehicle Assembly Building, he said they will wait to try again until mid-October after the next crew launches to the International Space Station. Artemis will take off from Launch Complex-39B. The SpaceX Crew Dragon missions lift off from the adjacent Launch Complex-39A. Crew-5 is scheduled for launch on October 3.

Rolling back to the VAB gives engineers access to much more of the 322-foot tall vehicle because it is surrounded by work platforms at many levels. But rolling it back and forth between the VAB and the launch pad, a four-mile journey that takes 8-12 hours each way, puts stress on the hardware so they’d like to do as few roll-outs and roll-backs as possible.

Jim Free, Associate Administrator for Exploration Systems Development, said they must roll back to the VAB because the battery on the Flight Termination System must be replaced and that cannot be done on the launch pad. Testing or replacing the battery 20 days after it is installed is a requirement of the U.S. Space Force, which administers the Eastern Range, for public safety reasons. If the rocket went off course, the FTS would be used to destroy it.

Space Force did give NASA a waiver for 5 more days this time to allow the possibilty of a launch on Monday. Free and Sarafin indicated they will ask for another waiver once they have a better idea of how long it will take to fix the leak.

Sarafin said he thinks they have “several weeks” of work ahead of them.

It seems unlikely such a lengthy extension would be granted.

But instead of explictly stating they will roll back, each would say only that they must roll back unless they get an extension.

It is also possible that whatever work is needed to fix the leak could require them to return to the VAB, but there are trade-offs. Sarafin pointed out, for example, that while being inside the VAB provides protection from the weather, they cannot test the QD with cryogenic fluids while it’s there. Cryo testing can only be done on the pad.

The bottom line is that they need time to assess the problem and options to fix it. Another briefing is planned during the coming week to provide an update.  Artemis I can only be launched at certain times when the Earth and Moon are correctly aligned. This NASA graphic shows upcoming opportunities. Gray and red blocks means they cannot launch, green means they can.  The difference between light green and dark green is whether it is a short duration or long duration mission.

This is the second launch scrub in five days. The first attempt on Monday was scrubbed not because of the hydrogen leak, but mainly because of readings that indicated one of the four Aerojet Rocketdyne RS-25 engines did not chill down to the required temperatures. Nothing was wrong with the engine. Instead, the problem was traced to a faulty sensor in the cooling system on the Core Stage side of the interface.

NASA is certain the problem was the sensor, but decided to start the engine chilldown earlier in the countdown to replicate conditions when the engines were successfully tested at Stennis Space Center last year. Today’s countdown did not progress far enough to use those new procedures so that will have to await the next launch attempt.

Asked how much two scrubs cost, Nelson quipped that whatever the amount, it is “a lot less than a failure.”

Artemis I is an uncrewed test flight of the Space Launch System rocket and Orion spacecraft around the Moon. Artemis II will be a crewed test flight around the Moon, while Artemis III will land the first humans on the Moon since the Apollo program. Nelson reiterated today that despite the delay with this launch, Artemis II is scheduled for 2024 and Artemis III for 2025.

 

Note: this article was updated throughout following the press conference this afternoon.