The piece, a structural test version of the intertank that will eventually be housed in NASA's Space Launch System, was loaded Thursday morning onto the agency's Pegasus barge. The barge, first used during the Space Shuttle program, will carry the intertank to the Marshall Space Flight Center in Huntsville, Alabama for testing.

The test piece is the second major core stage component built for the Space Launch System at Michoud, dubbed NASA's "rocket factory" for its decades-long role putting together the equipment that has carried astronauts to space. The engine section was delivered in May 2017.

The long-term vision for the 321-foot-tall Space Launch System, or SLS, is a manned mission to Mars, but the goal is to get it and its crew to the Moon first. The SLS will carry astronauts into deep space aboard NASA's Orion spacecraft, which was also built at Michoud and will sit atop the rocket.

At 48 feet high and and 27.6 feet in diameter, the intertank will connect the two giant fuel tanks on the 200-foot-tall core stage and serve as a connection point for the rocket's twin solid rocket boosters. It also houses the avionics and electronics NASA describes as the "brains" of the rocket.

The delivery of the intertank marks "significant progress toward the rocket's first flight," according to a news release.

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