Michoud Assembly Facility

NASA - Liquid Oxygen Tank - LOX/GWT Tool. Time Lapse Video.
NASA is charging ahead with the construction of their SLS (Space Launch System) rocket booster. It's a sizable construction project and in order to build the rocket they needed to build some tools. The video shows the erection of two specialized welding tools in the Enhanced Robotic Weld Tool. The two hemispherical scaffolding-like structures are the tools. The one on the left is the Gore Weld Tool and the one on the right is the Circumferential Dome Weld Tool.

They are using Friction Stir Welding to join the parts of the tanks. Stir welding is kind of weird in that it does not involve burning flammable gases or electrical arcs. It works with brute force, which kind of explains why they need such substantial jigs, which is essentially what these 'tools' are.

This is all being done in the Michoud Assembly Facility (MAF) in New Orleans, Louisiana.

MAF is one of the largest manufacturing plants in the world with 43 environmentally controlled acres under one roof, and it employs approximately 3,700 people. From 1961 to the end of the Apollo program in 1972 the site was utilized by Chrysler Corp to build the first stages of the Saturn I and Saturn IB, later joined by Boeing Corp to build the first stage of the Saturn Vs. From 1973 to 2010 it was used for the construction of the Space Shuttle's external fuel tanks by Martin Marietta Corp., Denver Colo.  

The facility was originally constructed in 1940 at the village of Michoud, Louisiana to make plywood C-76 cargo planes and landing craft. During the Korean War it made engines for Sherman and Patton tanks, and boasted a 5,500 foot paved runway. - Wikipedia