Technicians complete final welds Inside Liquid Oxygen Tank for first SLS flight

The liquid oxygen tank - shown here as technicians inside the tank complete final welds to plug holes left by the robotic welder - is undergoing the first hydrostatic testing for NASA’s deep-space rocket, the Space Launch System (SLS).

All five major parts - the engine section, liquid hydrogen tank, intertank, liquid oxygen tank and forward skirt - are built and ready for additional outfitting and testing.

They will be connected together to form the 212-foot-tall core stage, the backbone of the SLS rocket.

To build the two largest core stage structures – the liquid hydrogen and liquid oxygen tanks that hold more than 700,000 gallons of propellant – NASA welded the thickest structures ever joined using self-reacting friction stir welding.