Millimeter-Wave Directed Energy Deep Boreholes

The analytic basis of high temperature, full bore directed energy opening in rock is presented including energy requirements, rates of penetration, high temperature physics replacement of drilling mud, and diameter control. Millimeter-waves are ideally suited for long distance, high power guided transmission into typical borehole dimensions, but deep high pressure induced absorption will ultimately determine depth limits. The feasibility of this technology is established in the laboratory with granite and basalt specimens heated to temperatures in the 2500 - 3000 degree C range using a low power 10 kW, 28 GHz gyrotron. A possible application to an Enhanced Geothermal System (EGS) is described using an engineered heat exchanger (EHE) with a potential useful lifetime of 100 years.