NASA Continues To Work On Liquid Hydrogen Leak In Preparation Artemis I
The Space Launch System has been extremely busy as it continues to prepare for its first launch apart of Artemis 1. We recently watched some of the first attempts that were scrubbed for multiple reasons including a liquid hydrogen leak at the quick disconnect. This being said, over the past few weeks, the agency has been working to not only address these issues in the form of various fixes, but test them as well.
Specifically, just two days ago on the 21st, NASA performed a cryogenic demonstration test. The goal was to test whether or not the agency had fixed the leak, test new procedures, conduct the kick-start bleed, and perform a pre-pressurization test. However, it seems this test was only semi successful as a slight leak was still detected despite all the prior efforts to fix it.
As of right now, the agency is still somewhat targeting September 27th, and October 2nd for the upcoming launch dates of Artemis I. This being said, NASA wants to go over more of the recent test data before confirming or shifting the next launch dates. Here I will go more in-depth into the test itself, what exactly the result is, how it impacts the future of SLS launching, and more.
Cryogenic Demonstration Test
Earlier this week, NASA began preparing for the Cryogenic Demonstration Test. Specifically, days after the most recent launch attempt, teams analyzed the seals that were replaced on an interface for the liquid hydrogen fuel line between the Space Launch System (SLS) rocket and the mobile launcher and adjusted procedures for loading cryogenic, or supercold, propellants into the rocket. Engineers identified a small indentation found on the eight-inch-diameter liquid hydrogen seal that they thought could have been a contributing factor to the leak on the previous launch attempt. With new seals, updated cryogenic procedures, and additional ground software automation, teams began preparing to demonstrate the updates under the same cryogenic conditions the rocket will experience on launch day. During the demonstration, the four main objectives include assessing the repair to address the hydrogen leak, loading propellants into the rocket’s tanks using the new procedures, conducting the kick-start bleed, and performing a pre-pressurization test.
However, based on recent engineering assessments, NASA decided to do the procedure slightly differently than normal. The new cryogenic loading procedures and ground automation, transitions temperatures and pressures more slowly during tanking to reduce the likelihood of leaks that could be caused by rapid changes in temperature or pressure. Performing the pressurization test during the demonstration will enable teams to dial-in the necessary settings and validate timelines before launch day, reducing schedule risk during the launch countdown.
This brings us to the actual test just two days ago on the 21st. Early in the morning, NASA tweeted saying, “Launch Director Charlie Blackwell-Thompson has given the “go” to officially begin loading propellants into the Space Launch System rocket as part of today’s Artemis I cryogenic demonstration test.” After chilling the lines for liquid oxygen (LOX), teams began the slow fill phase to load LOX into the Space Launch System rocket’s core stage and started chilling down the transfer line for the liquid hydrogen (LH2). Next, NASA reported that the fast fill was underway for the Space Launch System rocket’s core stage liquid oxygen tank. However, soon after, launch controllers detected a hydrogen leak in a cavity in the tail service mast umbilical and stopped flowing the propellant to the rocket while they worked to troubleshoot the issue. About an hour and a half after this report, teams resumed the flow of liquid hydrogen into the core stage after warming up the quick disconnect, or interface where the fuel feed line connects to the rocket, to reseat the connection as part of their troubleshooting plan to fast fill the propellant. This quick fix seemed to have worked for the most part as the fast fill continued for SLS’s core stage liquid hydrogen tank at a reduced pressure as teams monitored the area where the hydrogen leak was detected.
The agency then reported that fast fill was complete for the core stage liquid oxygen tank and engineers had completed the engine bleed test, which flows supercold LH2 to the four RS-25 engines, bringing their temperature down to the conditions required for launch. From here, the liquid hydrogen tank was full and started being replenished as some of the supercold propellant boiled off. The agency pointed out that since resuming liquid hydrogen fast fill operations, the rate of the hydrogen leak at the tail service mast umbilical quick disconnect had remained within allowable rates. Soon after, launch controllers reached the replenishment phase of liquid hydrogen loading operations for the interim cryogenic propulsion stage of SLS and continued operations to load liquid oxygen into the upper stage. Finally, around 4 pm, launch controllers completed the pre-pressurization test, obtaining pressure and temperature level readings as desired.
Test Results & Future Dates
At around 5 pm on the 21st, the launch director confirmed all objectives had been met for the cryogenic demonstration test, and teams were proceeding with critical safing activities and preparations for draining the rocket’s tanks. After encountering a hydrogen leak early in the loading process, engineers were able to troubleshoot the issue and proceed with the planned activities. The four main objectives for the demonstration included assessing the repair to address the hydrogen leak identified on the previous launch attempt, loading propellants into the rocket’s tanks using new procedures, conducting the kick-start bleed, and performing a pre-pressurization test. The new cryogenic loading procedures and ground automation were designed to transition temperature and pressures slowly during tanking to reduce the likelihood of leaks that could be caused by rapid changes in temperature or pressure. After encountering the leak early in the operation, teams further reduced loading pressures to troubleshoot the issue and proceed with the demonstration test. The pre-pressurization test enabled engineers to calibrate the settings used for conditioning the engines during the terminal count and validate timelines before launch day to reduce schedule risk during the countdown on launch day.
NASA finished by saying, “Teams will evaluate the data from the test, along with weather and other factors, before confirming readiness to proceed into the next launch opportunity. The rocket remains in a safe configuration as teams assess next steps. In addition to the results of this test, there are a lot of different factors influencing the next date for an Artemis 1 launch attempt. Just over a week ago, NASA updated future dates to a possible launch on the 27th and a backup on October 2nd with all these considerations in mind. Specifically, the updated dates represent careful consideration of multiple logistical topics, including the additional value of having more time to prepare for the cryogenic demonstration test, and subsequently more time to prepare for the launch. The dates also allow managers to ensure teams have enough rest and to replenish supplies of cryogenic propellants.
NASA and SpaceX also continue to target no earlier than 12:45 p.m. EDT Monday, Oct. 3, for the launch of the agency’s Crew-5 mission to the International Space Station. Right now, teams are working on the upcoming commercial crew launch in parallel to the Artemis I planning and both launch schedules will continue to be assessed over the coming weeks. NASA and SpaceX will review the Artemis I and Crew-5 prelaunch processing milestones to understand any potential impacts. The agency’s Crew-4 return will continue to be planned following a short handover on the space station with Crew-5. It’s also important to point out that the agency is currently in a launch period that extends from September 19th to October 4th. If they decide they are not ready to launch within this period, the next launch period begins October 17th and goes to the 31st. These launch periods are based on a few necessary criteria including the Moon’s position, ensuring Orion is not in darkness for more than 90 minutes, supporting the skip entry technique, and ensuring splashdown is during the day. Not to mention that four days within the next launch period don’t support the Artemis 1 mission. This means that right now NASA is considering the results of this demonstration test, other launches like SpaceX Crew 5, and the different SLS launch periods. All of which will determine when exactly the next launch attempt is.
Conclusion
NASA has been working hard to try and get the Space Launch System up and running for the Artemis I mission. After two scrubbed launch attempts, the agency took its time to repair a reoccurring liquid hydrogen leak that was responsible for multiple problems. Just two days ago they had a mostly successful cryogenic demonstration test and are deciding right now when the next launch attempt will be. We will have to wait and see how it progresses and the impact it has on the space industry.