Reply To: Richard Branson – Virgin Pledge

[Duke Leto]

OK, I’ve looked things over, and I think that the bleaker projection on the idea may be correct.

First, most modern subterranean mining uses a technique called the “longwall”, where a large extraction mechanism processes a coal seam in its entirety while supports are held over it. As the material is extracted, the supports are advanced and the material is allowed to fill the now vacant space.

Ergo, no tunnels.

So it would only be OLD mines that would be useful, and therefore the least stable.. And then again there would be the startup expense of sealing, which would need to be a double sealant using one layer a to a cover the rock, some kind of intermediary liquid with sensors to find disturbances in said liquid from ruptures, and an outer layer. And then in aquaculture added supports would be needed to take care of the dangers of subsidance caused by the weight of the water.

All very expensive…