The first Canadian astronaut mission to the Moon will wait at least a month after NASA achieved partial successes on a 49-hour fueling test of the rocket, also known as the Space Launch System or SLS.
The tanking – which concluded early on Tuesday, roughly five days ahead of the previous launch window that opened Feb. 8 – aimed to fill both the core stage and the upper stage (interim cryogenic propulsion stage) of SLS with liquid oxygen and liquid hydrogen.
While NASA appeared to make more progress on the first “wet dress rehearsal” (WDR) of Artemis 2 compared to predecessor Artemis 1’s mission first attempts in 2022, the agency concluded that not all objectives were met and that another WDR would be needed.
In a press conference held Tuesday, however, agency officials said it appears that any issues uncovered can be addressed at the pad, meaning that the rocket will not be rolled back to the Space Launch System for analysis (at least immediately, as batteries for the flight termination system will expire if the rocket doesn’t launch in March).
But NASA emphasized that they are just beginning to dig into the results for the WDR. A new date for WDR has not yet been set, as more analysis and testing will need to be done ahead of that point.
“To me, the big takeaway was we got a chance for the rocket to talk to us, and it did just that. The test gave us exactly what we needed. It was an opportunity for us to wring out the system as a team before we asked our crew to go fly,” said John Honeycutt, chair of the Artemis 2 mission management team, at the livestreamed press conference at NASA’s Kennedy Space Center in Florida.
Lori Glaze, acting associate administrator for NASA’s Exploration Systems Development Mission Directorate, elaborated on some of the lessons learned. These included gathering more data on nitrogen purging/hydrogen leaks (with the aim to reduce these issues in the future), and pointing out the complexity and number of steps required to close the hatches on the crew module and the launch abort system.
She emphasized she was in touch with the crew – which includes Canadian Space Agency astronaut Jeremy Hansen – throughout the test and that the agency has “implemented a lot of the lessons learned from Artemis 1,” showing progress. But more progress will be required before certifying Artemis 2 for launch, which means the four astronauts (Hansen, and NASA’s Reid Wiseman, Victor Glover and Christina Koch) were released from quarantine earlier on Tuesday.
Previous to the press conference, the agency noted that it did successfully load cryogenic propellant into all SLS tanks, and sent a closeout team to the pad for simulated checks on the Orion spacecraft prior to launch.
These are some of the issues NASA stated in its press release (the quotes are from the agency).
- The cold: Record cold temperatures have been happening across the U.S., including in Florida, which affected tanking operations. “Cold temperatures caused a late start to tanking operations, as it took time to bring some interfaces to acceptable temperatures before propellant loading operations began.” The agency said the cold also caused issues with cameras “and other equipment” that did not interfere with the WDR, but which “would have required additional attention on launch day.”
- Leaking during loading: “During tanking, engineers spent several hours troubleshooting a liquid hydrogen leak in an interface used to route the cryogenic propellant into the rocket’s core stage, putting them behind in the countdown. Attempts to resolve the issue involved stopping the flow of liquid hydrogen into the core stage, allowing the interface to warm up for the seals to reset, and adjusting the flow of the propellant.”
- A leak late in the countdown: NASA was able to move forward with filling all the SLS tanks and sending out the closeout crew, next doing a terminal countdown operations test. But with about five minutes left in the countdown, “the ground launch sequencer automatically stopped the countdown due to a spike in the liquid hydrogen leak rate.”
- Orion pressurization/closeout issues: NASA also found “a valve associated with Orion crew module hatch pressurization, which recently was replaced, required retorquing, and closeout operations took longer than planned.”
- Audio dropouts: NASA observed several communications dropouts during WDR, following on from issues it has been troubleshooting prior to the test.
Reporters at the press conference noted that hydrogen leaks had been a feature of WDR attempts during Artemis 1, three years ago. But the agency said the molecule is small (meaning it is hard to contain), and the particular interface where the leaks often happened is “complex”.
This interface is known as the tail service mast umbilical. Two TSMUs connect the mobile launcher to the SLS rocket core stage aft section and are each 33 feet tall, according to NASA documentation. Each umbilical includes fluid lines for liquid oxygen and liquid hydrogen, as well as electrical cable connections (with all lines being severed before launch after the umbilicals tilt back).
“We like to test like we fly, but this interface is a very complex interface – and when you’re dealing with hydrogen, it’s a small molecule, it’s highly energetic,” Honeycutt said. “We do the best we can. This one caught us off-guard.”
Charlie Blackwell-Thompson, Artemis launch director, also noted the success in implementing a contingency procedure developed after Artemis 1; when the first leak happened in the TSMU during Artemis 2’s WDR, engineers paused fueling, warmed up the quick-disconnect seal and then attempted resuming. “We did that a couple times, worked our way through it and [were] able to load the core stage all the way to replenish.”
She said that concentrations of hydrogen appeared to be within limits during the slow-fill phases of the fueling, but these concentrations rose during fast-fill. Stop flows were triggered at 16% concentration, but she said the team was able to manage the issue through three contingencies.
Blackwell-Thompson added that the team had hoped to reach the terminal count, hold it for 10 minutes and then recycle for another terminal count. This will be tried again during the next WDR.
NASA also responded to some long-term considerations for Artemis.
- A reporter raised on X on Tuesday that SLS has a low flight rate, and NASA administrator Jared Isaacman issued a lengthy statement in response. Among his points was that the low flight rate is precisely why WDR happens – for safety considerations – and that SLS is meant to “achieve our near-term objectives through at least Artemis 5.” Isaacman also alluded to industry, saying it would take on some capabilities from NASA for the later phases of the Artemis program, but did not outline a pathway or the specific impacts to SLS. When asked about this statement at the press conference, and whether commercial providers would be considered in the near term for launch, associate NASA administrator Amit Kshatriya said the preference is “to let industry innovate on their own machines” before making changes to the launch architecture.
- Kshatriya also spoke to a question about the Trump administration’s preference to land Artemis 3 on the Moon in 2028, which was also recently expressed in an executive order. In sum, he said NASA is not feeling any schedule pressure from the administration, but rather, “we feel the pressure to make sure that we’re listening to the machine, and we’re doing the right thing for the crew. I would tell you that. We put that pressure on ourselves to be successful.” As for Artemis 3, he added, there are other considerations beyond SLS – the lander and the spacesuits, specifically. But the core stage for SLS will be delivered to KSC within a few months.