Spaceflight Insider

Problems aside, NASA moves toward SLS structural testing at Marshall

SLS Core Stage Production

NASA and Boeing have cleared the component, shown here, for use as the bottom of the dome of an SLS liquid oxygen tank structural test article. After the dome is welded to the rest of the test article in the Vertical Assembly Center, right, it will undergo inspection and processing before being shipped from the Michoud Assembly Facility in New Orleans to NASA’s Marshall Space Flight Center in Huntsville, Alabama, for structural testing. Photo & Caption Credit: Judy Guidry / NASA / MSFC

Moving beyond site selection controversy and production problems that caused headlines in May, NASA is working to complete a Space Launch System (SLS) structural test article at the Space Agency’s Michoud Assembly Facility (MAF) in Louisiana.

Welding concerns


Early in May, workers discovered that the forward liquid oxygen tank dome had been damaged during welding, raising concerns the item would be useless for structural tests planned at Marshall Space Flight Center in Alabama. However, engineers from NASA and prime contractor Boeing have now cleared the dome for use and completed repairs to the MAF’s specialized friction stir welding assembly.

Much of the hardware necessary for the structural tests on the SLS core stage has already been completed. The engine section, which will mount four RS-25 engines, was shipped to Marshall in April. The liquid hydrogen tank welding was completed in September of last year, and the intertank section was recently completed. Among the major test items, only the liquid oxygen tank remains unfinished. Meanwhile, Boeing has begun welding the first flight-intended liquid hydrogen tank.

SLS Core Stage Production

Engineers assembled the structure of the intertank that will be flown on the first Space Launch System integrated flight with Orion. The intertank, one of five parts of the 212-foot core stage being built and assembled at NASA’s Michoud Assembly Facility in New Orleans, is on its way to undergo the application of thermal protection systems. The intertank is the only major structural part of the core stage that is not welded. It is made of eight large panels which are connected with 7,500 bolts. The 22-foot-tall structure carries most of the massive launch load produced by the solid rocket boosters that separate from the core stage about two minutes after launch. Photo & Caption Credit: Judy Guidry / NASA / MSFC

 

SLS Core Stage Production

The Space Launch System intertank, shown here moving down the factory floor, finished structural assembly at NASA’s Michoud Assembly Facility in New Orleans. Technicians moved it to an area where it will be coated with a thermal protection system. The yellow object (left back) is the engine section of the core stage, which also completed structural assembly and is being outfitted with propulsion system hardware that will feed fuel to the four RS-25 engines on the first SLS mission. Photo & Caption Credit: Judy Guidry / NASA / MSFC

Preparation for testing


The completed test articles will be qualified at a Marshall-based test stand that NASA’s Inspector General harshly criticized in a May report. The IG found that NASA did not adequately consider alternate locations, such as Stennis Space Center in Mississippi, where NASA already hosts rocket engine testing. It noted that the journey by barge from Michoud to Marshall required two weeks of travel for each test component – on a barge that could only carry one piece at a time – requiring six weeks total of travel and a total cost of over $1 million.

The entire test article could be shipped to Stennis within a week at a total cost of around $200,000.

The IG also criticized the space agency for not considering life cycle costs and ordering construction based on incomplete designs and specifications. The report recommended that stricter procedures govern NASA’s testing construction in the future, but noted that it was too late to move the test stands as NASA was moving ahead quickly with its test schedule.

LEFT IMAGE: NASA cleared the dome, shown here being removed from the infeeder tool, for use as intended as the bottom dome of the liquid oxygen tank structural test article being welded in the Vertical Assembly Center, right. The dome sustained minor damage during operations May 3, 2017. The investigation team is currently wrapping up their investigation of the mishap and will prepare recommendations to the SLS program. RIGHT IMAGE: More than 500,000 U.S. gallons of fuel will flow from the liquid hydrogen tank to the four RS-25 engines that power NASA’s Space Launch System rocket. During a flight, and even during testing, a tank’s insides must be clean to ensure contaminants do not find their way into complex propulsion and engine systems. Technicians recently lifted the liquid hydrogen tank structural qualification test article into a cleaning cell at NASA’s Michoud Assembly Facility in New Orleans where its insides will be thoroughly cleaned, coated, and dried to certify the process for the following flight article. Photo & Caption Credits: Judy Guidry / NASA / MSFC

 

SLS Core Stage Production

The bottom of a Space Launch System liquid hydrogen fuel tank test article is visible as it is lowered into a cleaning cell at NASA’s Michoud Assembly Facility in New Orleans where the tank was manufactured. Technicians will clean the inside of the tank to remove any potential contaminants. Photo & Caption Credit: Judy Guidry / NASA / MSFC

The liquid hydrogen tank test article is currently waiting for shipment to Marshall, and the liquid oxygen tank lacks only the aft dome before welding on it is completed. The intertank section, which is bolted together, rather than welded, is also waiting for shipment to Marshall.

Once all the components arrive at the test stands in Alabama, they will be subjected to structural tests to certify the SLS design for flight by simulating the stresses the heavy-lift rocket will experience during its launch and ascent.

 

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Christopher Paul has had a lifelong interest in spaceflight. He began writing about his interest in the Florida Tech Crimson. His primary areas of interest are in historical space systems and present and past planetary exploration missions. He lives in Kissimmee, Florida, and also enjoys cooking and photography. Paul saw his first Space Shuttle launch in 2005 when he moved to central Florida to attend classes at the Florida Institute of Technology, studying space science, and has closely followed the space program since. Paul is especially interested in the renewed effort to land crewed missions on the Moon and to establish a permanent human presence there. He has covered several launches from NASA's Kennedy Space Center and Cape Canaveral for space blogs before joining SpaceFlight Insider in mid-2017.

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