NASA prepares to complete Artemis SLS rocket structural testing

The liquid oxygen tank structural test article, shown here, for NASA’s Space Launch System (SLS) rocket’s core stage was the last test article loaded into the test stand July 10, 2019. The liquid oxygen tank is one of two propellant tanks in the rocket’s massive core stage that will produce more than 2 million pounds of thrust to help launch Artemis I, the first flight of SLS and NASA’s Orion spacecraft to the Moon. Now, the tank will undergo the final test completing a three-year structural test campaign at NASA’s Marshall Space Flight Center in Huntsville, Ala. Tests conducted during this campaign put the rocket’s structures from the top of the upper stage to the bottom of the core stage through strenuous tests simulating the forces that the rocket will experience during launch and flight. All four of the core stage structural test articles were manufactured at NASA’s Michoud Assembly Facility in New Orleans and delivered by NASA’s barge Pegasus to Marshall. (NASA photograph by Tyler Martin)

NASA’s Space Launch System Program is concluding its structural qualification test series with one upcoming final test that will push the design for the rocket’s liquid oxygen tank to its limits at NASA’s Marshall Space Flight Center in Huntsville, Ala.

In the name of science, engineers will try to break a structural test article of the tank–on purpose. The liquid oxygen tank’s structure is identical to the tank that is part of the SLS core stage, which will provide power to help launch the Artemis missions to the Moon. The tank is enclosed in a cage-like structure that is part of the test stand. Hydraulic systems will apply millions of pounds of force to push, pull and bend the liquid oxygen tank test article to see just how much pressure the tank can take. The forces simulate what the tank is expected to experience during launch and flight. For the test, the tank will be filled with water to simulate the liquid oxygen propellant used for flight, and when the tank ruptures, the water may create a loud sound as it bursts through the tank’s skin.

“We take rocket tanks to extreme limits and break them because pushing systems to the point of failure gives us a data to help us build rockets more intelligently,” said Neil Otte, chief engineer for the SLS Stages Office at Marshall. “Breaking the propellant tank today on Earth will provide us with valuable data for safely and efficiently flying SLS on the Artemis missions to the Moon.”

Earlier this year, NASA and Boeing engineers subjected the tank to 23 baseline tests that simulate actual flight conditions, and the tank aced the tests. The tank is fitted with thousands of sensors to measure stress, pressure and temperature, while high-speed cameras and microphones capture every moment to identify buckling or cracking in the cylindrical tank wall. This final test will apply controlled forces stronger than those engineers expect the tank to endure during flight, similar to the test that ruptured the liquid hydrogen tank and created noise heard in some Huntsville neighborhoods near Marshall.

This is final test in a series of structural qualification tests that have pushed the rocket’s structures to the limits from top to bottom to help ensure the rocket is ready for the Artemis lunar missions. Completion of this upcoming test will mark a major milestone for the SLS Program.

The Marshall team started structural qualification testing on the rocket in May 2017 with an integrated test of the upper part of the rocket stacked together: the Interim Cryogenic Propulsion Stage, the Orion stage adapter and the launch vehicle stage adapter. Then the team moved on to testing the four largest structures that make up the 212-foot-tall core stage. The last baseline test for Artemis I was completed in March 2020 before the team’s access to Marshall was restricted because of the COVID-19 pandemic. The NASA and Boeing team returned to work the first week in June to prepare for conducting the final liquid oxygen test to failure. 

The structural qualification tests help verify models showing the structural design can survive flight. Structural testing has been completed on three of the largest core stage structures: the engine section, the intertank, and the liquid hydrogen tank. The liquid oxygen tank has completed baseline testing and will now wrap up core stage testing with the upcoming test to find the tank’s point of failure.

“The liquid oxygen tests and the other tests to find the point of failure really put the hardware through the paces,” said April Potter, the SLS test project manager for liquid oxygen and liquid hydrogen structural tests. “NASA will now have the information to build upon our systems and push exploration farther than ever before.”

The SLS rocket, Orion spacecraft, Gateway and human landing system are part of NASA’s backbone for deep space exploration. The Artemis program is the next step in human space exploration. It is part of America’s broader Moon to Mars exploration approach, in which astronauts will explore the Moon and gain experience to enable humanity’s next giant leap, sending humans to Mars.

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