NASA is counting down to 29 seconds from the launch of a large SLS rocket

Zoom in / NASA’s Space Launch System rocket, which is reflected in the vault pool in the Kennedy Space Center in Florida, will launch its fourth attempt at the wet general test on June 6, 2022.

Trevor Mahlmann

NASA tried three times during April to complete a critical test of the charge of its large Space Launch System rocket. And three times, due to about half a dozen technical problems, the space agency failed.

And so NASA made the difficult decision to return the large rocket to the vehicle assembly building for repairs, adding several months of delay to a program that has been delayed for years. After this work was completed in early June, NASA returned the SLS rocket and the Orion spacecraft to the launch pad in the fourth attempt.

It turned out that the painful decision was the right one. For more than 14 hours on Monday, NASA largely succeeded in completing this refueling test, loading hundreds of thousands of gallons of liquid oxygen and hydrogen into 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, launch director of Artemis.

She and other NASA officials joined a press conference on Tuesday to discuss the results of the fourth “wet dress rehearsal” test, which aims to work out the inclinations of the rocket’s countdown to takeoff before launch day. To that extent, the test seemed to have largely succeeded. NASA reached the T-29 seconds after taking off during the test, close to its predicted target of T-9.3 seconds, before completing the test just before launching the rocket’s four main engines.

During the teleconference, NASA officials declined to answer specific questions about whether a fifth test would be needed – to reduce the countdown to T-9.3 seconds – or when the rocket could be ready for its debut launch. Citing a desire to review more data, officials said they expect to provide this information in a few days. From their comments, however, it sounded as if officials might be relying on the fifth test.

Several technical problems occurred during the test on Monday, the most significant of which was a hydrogen leak in a quick disconnection at the bottom of a mobile launch tower that supports an SLS rocket while refueling. This 4-inch hydrogen line is one of several that are released from the rocket just before takeoff and are connected to the tail service mast of the tower.

NASA failed to solve the problem with the seal that did not leak during the last part of the test from Monday, so instead it decided to cover up the leak from the sequencer for launching from the ground, a computer on the ground that controls most counts. This posed no risk to the rocket during the test, but should be corrected before the actual launch.

With this part of the disguise, NASA’s launch team managed to go from T-10 minutes to T-29 seconds and demonstrate the ability not only to fill the SLS rocket but also to keep its fuel tanks full. When the ground launch sequencer handed the rocket to the computer for the last part of the countdown, the flight computer automatically stopped counting.

NASA officials liked what they saw. “This is the first time we have been in a completely cryogenic environment at both the primary and upper stages,” Blackwell-Thompson said. “Terminal counting is a very dynamic time. I totally expected that we might have one or two things we might need to discuss in the terminal count, but it was extremely smooth. There was nothing to talk about. “

This refueling test is the last major hurdle between the SLS rocket and the launch attempt later this year. There is still work to be done, and the agency must decide whether another test of wet dressing is necessary. But Mike Sarafin, the manager of the Artemis I mission, said that he believes that NASA has fulfilled about 90% of the test goals so far.

In addition to repairing the leaking hydrogen seal, NASA still needs to return the rocket to the vehicle assembly building to install and activate the end-of-flight system. This work probably prevents the launch attempt by the end of September at the earliest.

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