Comment by bkeroack

It seems to me that there may be room for disruption. Currently every TBM (tunnel boring machine) is completely bespoke and is used for exactly one project and is then dismantled/recycled. They cost hundreds of millions of dollars each. I imagine there are relatively few manufacturers out there building TBMs.

Actually in some ways it bears a resemblance to the spaceflight industry (expensive, custom-made, few players). Coincidence?