Spaceflight Insider

NASA moving forward with modified fueling test for SLS rocket

NASA's SLS rocket sits on the pad for a wet dress rehearsal in advance of the Artemis 1 mission later this year. Credit: Derek Richardson / Spaceflight Insider

NASA’s SLS rocket sits on the pad for a wet dress rehearsal in advance of the Artemis 1 mission later this year. Credit: Derek Richardson / Spaceflight Insider

NASA said it is modifying the wet dress rehearsal for the giant Space Launch System in advance of the uncrewed Artemis 1 mission around the Moon.

This comes after two scrubbed test attempts during the first week of April 2022. On April 11, the agency said a faulty helium check valve was found in the upper stage of the rocket — the interim cryogenic propulsion stage, or ICPS.

During a teleconference, NASA said the check valve was not functioning as expected. Replacing it requires a rollback to the Vehicle Assembly Building as there is no easy access to its location while at Launch Complex 39B.

Credit: Theresa Cross / Spaceflight Insider

Credit: Theresa Cross / Spaceflight Insider

However, in order to move forward with the wet dress rehearsal, this prompted changes to testing in order to ensure the safety of the flight hardware and necessitated a modified test process.

The ICPS is the upper stage of the SLS rocket. For the wet dress rehearsal, it will have an abbreviated role in the test while the core stage of the vehicle is the only stage that will be fully-fueled during the test.

Some propellants are expected to be moved into the ICPS, however NASA said only a minimal amount will be transferred in order to get to cryogenic temperatures.

That test — the third attempt — started at 5 p.m. EDT April 12 and will extend through April 14. The targeted “T-minus zero” for the test is 2:40 p.m. EDT (18:40 UTC) Thursday.

Testing on Thursday for the wet dress rehearsal is significant as teams are planning to load and drain propellant on the core stage, getting into the terminal countdown operations of the behemoth rocket. NASA also plans to perform some chill down operations on the core stage.

The test will go all the way into terminal count, stopping just a few seconds before the four RS-25 engines would ignite for the actual flight.

NASA teams say they are confident that even though this is a modified test. Engineers during a press conference on April 11 said the data collected should help the agency meet its objectives ahead of launch.

“We believe that this is the best option moving forward,” Charlie Blackwell-Thompson, NASA’s Artemis launch director, said during the teleconference. “We believe that we’ll be able to meet the majority of our test objectives and provide us with a reasonably good set of data prior to rollback.”

The ICPS, Orion spacecraft and launch abort system at the top of the SLS rocket. Credit: Michael McCabe / Spaceflight Insider

The ICPS, Orion spacecraft and launch abort system at the top of the SLS rocket. Credit: Michael McCabe / Spaceflight Insider

Successful launch control interface has been completed allowing engineers to collect data from the Mobile Launcher and Orion spacecraft.

The issue at hand that ultimately caused the modified wet dress rehearsal was a helium leak identified from an inlet fitting down in the Mobile Launcher base. This was found during the second test attempt last week.

The inlet valve is crucial for helium control pressure that ultimately provides helium to the upper composite overwrapped pressure vessels, known as COPVs.

Teams investigating the faulty fitting, replaced the valve enabling them to reduce pressure on the COPVs.

Once the team pressurized the system to test the newly replaced check valve, technicians failed to see the numbers they were looking for.

Further trouble shooting indicated the problem was on the flight side of the interface triggering modifications for the tests last Thursday until the rocket rolls back to the Vehicle Assembly Building for complete analysis of the helium purge system.

During the April 11 teleconference, NASA engineers and managers said they will decide on the next steps after the wet dress rehearsal. Under the original plan, the rocket is to be rolled back to the Vehicle Assembly Building to be readied for the Artemis 1 mission later this summer.

It’s unclear whether another wet dress rehearsal will be attempted after the helium check valve is replaced.

When Artemis 1 is finally ready to launch, it has three windows during the summer months. Those are June 6 to June 16, June 29 to July 17 and July 26 to Aug. 9.

The SLS rocket is set to send an uncrewed Orion spacecraft to the Moon to spend several weeks in a distant retrograde lunar orbit to test its various systems. At the conclusion of its mission, the capsule is expected to return to Earth, splashing down in the Pacific Ocean.

Video courtesy of NASA


Theresa Cross grew up on the Space Coast. It’s only natural that she would develop a passion for anything “Space” and its exploration. During these formative years, she also discovered that she possessed a talent and love for defining the unique quirks and intricacies that exist in mankind, nature, and machines. Hailing from a family of photographers—including her father and her son, Theresa herself started documenting her world through pictures at a very early age. As an adult, she now exhibits an innate photographic ability to combine what appeals to her heart and her love of technology to deliver a diversified approach to her work and artistic presentations. Theresa has a background in water chemistry, fluid dynamics, and industrial utility.

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