Space Shuttle main tank friction-stir welding

Physical sample held up. Student thesis project ca. early 1990s.

There are lots of joining technologies for other things. [Tom holds up a friction stir weld sample.] This is a piece of friction-stir-welded aluminum. A student came to me, wanted to work for NASA. This is how they put together part of the Space Shuttle main tank. Distortion-free, or relatively distortion-free, friction stir weld. Boeing went out and spent ten million dollars building a friction stir welding machine for some of their structures, because a welded joint is always lighter than a bolted joint.