The latest information is that Deep Digger as being able to dig down to 150 feet, which is deeper than the best brute force approach. (Blu-113 a 4600 lb missile that is optimized for underground penetration reachs about 100 feet of dirt and 22 feet of concrete. In the ‘Concept Of Operations’ on Slide 4: an array of 20 Deep Diggers would be detonated together to produce a shockwave which will collapse all underground structures to a depth of 300 feet over a 200-yard square area. This would be even deeper than the nuclear bunker buster. The nuclear bunker buster has a maximum yield of 340 kilotons, the destruction depth would be roughly 70 meters [ =210 feet ] for a hardened target.
Deep Digger has some key advantages over earlier weapons:
- Deep penetration means that all of the blast goes into creating an underground shockwave, not just digging a crater. For blasting rock, it’s basic that the charge need to be drilled to a depth to be effective.
- Deep Digger parachutes down to a soft landing before digging in. Other bunker busters hit the ground very hard and experience a deceleration tens of thousands of g's. This affects their reliability, and the loss of a few warheads may make the whole array ineffective.
- Deep Digger may be able to maneuver underground, correcting the configuration of the array after it is in place.
And Deep Digger is only a first-generation active penetrator. Devices like General Dynamics Worm which Noah described last week may burrow much more effectively.
The worm digging machine is described in this pdf
Bunkers can always be dug deeper. One British Cold War plan involved relocating government centres to coal mines 5,000 feet underground. Successful Deep digger devices would make the vast majority of existing bunkers obsolete or insecure. If Deep diggers are more effective than nuclear bunker busters that could eliminate the need for the nuclear devices.