Bay Area start-up Earthgrid said it is developing a plasma-drilling robot capable of digging underground tunnels 100 times faster and up to 98% cheaper than existing technology, and plans to to use it to start rewiring America’s energy, internet and utility networks. New Atlas Reports: Most of the tunnels dug today are made by huge mechanical rotary drills, which scrape the cutter wheels against the rock and shovel debris out behind them, lining the tunnel walls as they go. It’s extremely slow, extremely expensive, and the cutting heads and bits often need to be changed or serviced. But there is another way to cut through the toughest rock, as we highlighted in our January article on Petra’s thermal drilling robot. Blasting rock at high temperatures can fracture and vaporize the stone in a process called spallation, and blasting this damaged rock with high pressures causes it to flake, flake, and fly away.
You can do this without touching the rock walls at all, so the equipment can go through entire tunnels without stopping if necessary. It can run entirely on electricity, opening up the possibility of completely emissions-free drilling, and Petra and Earthgrid say it’s much, much faster and cheaper than doing things mechanically – to the point where projects previously unachievable can become economically viable. Earthgrid doesn’t appear to be as advanced as Petra – indeed, it is currently operating on pre-seed funding. But his intellectual property takes a boring spallation robot like Petra’s to the next level, placing multiple 27,000C (48,600F) plasma torches on large disks held in front of a “Rapid Burrowing Robot (RBR).” The flares are arranged in a Fibonacci spiral, starting from the center and widening out to cover the entire diameter of the bore.
Where Petra’s Thermal Drill Robot moves its head to widen its hole, the RBR will fire all the torches at once and rotate the torch-bearing discs to provide full coverage, blasting the rock backwards and forwards. collecting it in small carts, each connected along the cable supplying electricity to the drill. This cable will need to handle some serious juice. In estimates submitted for a patent, Earthgrid founder Troy Helming describes a potential embodiment of the concept using 72 plasma torches to drill a 1 meter (3.3 ft) bore. In its low-power state, with each torch consuming 500 kW, Helming estimates a total power consumption of 40 megawatts. If you need to crack, the high power state would consume up to 120MW constant. This is for a hole you can barely crawl through; to triple the diameter and create a utility-sized tunnel that you can comfortably walk through on level ground, you need to attach a larger “mother platform” behind the front platform. And if you wanted to upgrade to a 10m (33ft) tunnel that you could fit a few lanes of traffic through, you’d need to attach another, even larger “father’s rig” behind it. Total power consumption in a “stage 3” system like this could be as high as 1.38 gigawatts – but that’s by no means the limit; upgrading torches to higher power units would get the job done much faster, if an even more epic amount of power became available. How fast can Earthgrid dig a tunnel? The company says it can drill up to 1 km (0.62 miles) per day, which it says is up to 100 times faster than existing drills. They also estimate that a low-cost setup could cost as little as $300 per meter (3.3 feet) of tunnel.
“The company says it will sell drilling as a service or build, own, operate and maintain tunnels for customers seeking a long-term lease or tolling arrangement,” New Atlas adds. “But it also hopes to put in place enough interconnected customer projects to create an underground network spanning the entire contiguous United States.”