Another spinoff from hot fusion research money:
gyrotrons for ultra-deep drilling!
Indeed, gyrotrons capable of generating continuous energy beams over a megawatt in power are now becoming available, and that's amazing news for deep drillers. "The scientific basis, technical feasibility, and economic potential of directed energy millimeter wave rock drilling at frequencies of 30 to 300 GHz are strong," wrote Ogilvy. "It avoids Rayleigh scattering and can couple/transfer energy to a rock surface 1012X more efficiently than laser sources in the presence of a small particle extraction plume. Continuous megawatt power millimeter-waves can also be efficiently (>90 percent) guided to great distances (>10 km) using a variety of modes and waveguide (pipes) systems, including the potential of using smooth bore coiled and jointed/ joined tubing."
"Thermodynamic calculations," he continued, "suggest a penetration rate of 70 meters/hour (230 ft/hour) is possible in 5 cm (1.97 in) bores with a 1-MW gyrotron that couples to the rock with 100 percent efficiency. Use of lower- or higher-powered sources (e.g. 100 kW to 2 MW) would allow changes in bore size and/or penetration rate."