Trevor Mohlman
Three times during the month of April, NASA attempted to complete a critical fuel test of its massive rocket for the Space Launch System. And three times, due to about six technical problems, the space agency failed.
And so NASA made the difficult decision to return the massive rocket to the Vehicle Assembly Building for repair, adding two months of delay to a program already years behind schedule. After this work was completed in early June, NASA returned the SLS rocket and Orion spacecraft to the launch pad for a fourth attempt.
It turned out that the painful decision was the right one. Over the course of more than 14 hours on Monday, NASA was able to complete this refueling test, transferring hundreds of thousands of gallons of liquid oxygen and hydrogen to the first and second stages of the SLS rocket.
“It was a long day for the team, but I think it was a very successful day for the team,” he said. Charlie Blackwell Thompson, Artemis launch director.
She and other NASA officials took part in a conference call with reporters Tuesday to discuss the results of the fourth “experimental” test, which is aimed at figuring out the inflections of the rocket’s countdown to launch day. To that extent, the test appears to have been largely successful. NASA entered within T-29 seconds of take-off during the test, close to its intended target of T-9.3 seconds, before ending the test before igniting the rocket’s four main engines.
During the conference call, NASA officials declined to answer specific questions about whether a fifth test was needed — to reduce the count to T-9.3 seconds — or when the rocket would be ready for its first launch. Claiming that they would like to review more data, officials said they expect to provide that information within two more days. However, it appears from your comments that the officials may be leaning towards the fifth test.
A number of technical problems occurred during Monday’s test, the most significant of which was hydrogen leakage from a quick disconnect at the bottom of the movable launch tower supporting the SLS rocket during refueling. This 4-inch hydrogen line is one of several that are launched from the rocket shortly before takeoff and are attached to the turret’s tail service shaft.
NASA was unable to resolve the leak during the final part of Monday’s testing, so it chose to hide the leak from the ground sequencer, the computer on the ground side that controls most of the countdown. This did not pose any danger to the missile during testing, but it would have to be repaired before the actual launch.
With that little bit of concealment, the NASA launch team was able to go from T-10 to T-29 minutes and demonstrate the ability to not only fill the SLS rocket, but also maintain its fuel tanks. When the ground launch regulator was handed over to the onboard computer of the rocket for the final part of the countdown, the flight computer automatically finished the countdown.
NASA officials liked what they saw. “This is the first time we’ve experienced an extremely cold environment in both primary and upper grades,” Blackwell Thompson said. “The final count is a very dynamic moment. I was hoping we would have a thing or two that we could talk about in the final count, but it went really smoothly. There was nothing to talk about.”
The refueling test is the last major hurdle between the SLS missile and its launch attempt later this year. There is still work to be done, and the agency must decide if wet suit testing is necessary. But Mike Sarafin, Artemis I mission manager, said he believes that so far, NASA has completed about 90% of test goals.
In addition to fixing the leaking hydrogen seal, NASA still needs to return the rocket to the Vehicle Assembly Building to install and arm the flight termination system. This work is likely to prevent a launch attempt before the end of September at the earliest.
