NASA took a big step forward in preparations to test its Space Launch System core stage beginning on Aug. 7 with a 20-foot repositioning of the Main Propulsion Test Article (MPTA) structure on the B-2 Test Stand at Stennis Space Center. The existing MPTA framework structure, built in the late 1970s to support testing of the space shuttle MPTA, stands 61 feet high and contains about 1.2 million pounds of fabricated steel. It was shifted atop its test stand base platform (known as the “battleship”) to accommodate the SLS core stage, which is taller than the Apollo/Saturn first stage and the space shuttle MPTA. After the move, another 1 million pounds of steel will be added to extend the structure 100 feet higher, a task targeted for completion by year’s end. The repositioned MPTA structure and the added superstructure serve several purposes: to hold the core stage in place, absorb and direct the thrust generated by testing the stage and provide worker access to the core stage. Core-stage testing will involve the simultaneous firing of four RS-25 rocket engines, generating the same 2 million pounds of thrust that will help lift the SLS in actual flight. As designed, the SLS thrust will be directed through the new superstructure and the MPTA structure to the battleship base platform and down into the foundation of the test stand. Movement of the MPTA structure involved a number of steps. Crews worked to weld reinforcing steel plates and runners onto the structure to ensure it maintained structural integrity during the move. The structure then was unbolted from the battleship base platform and jacked up to facilitate movement. By “re-purposing” the MPTA structure, considerable cost-savings were achieved. The B-2 stand actually is one-half of a dual-position engine test structure. The B-1 test position is used by Aerojet Rocketdyne to test RS-68 rocket engines. Work on both stands can be coordinated; in fact, an RS-68 engine test was conducted on Aug. 5, just two days before MPTA repositioning began. To view a YouTube clip on the MPTA move, visit: http://youtu.be/J2Lzftbep6k