Thermal Analysis of Some Subterrene Penetrators

Various types of rock melting drills have been designed at Los Alamos. These have included density consolidating penetrators up to 90 mm in diameter of varying configurations. A number of these consolidators have been tested in loams, alluvium, and tuff. Extruders up to 87 mm in diameter designed for an improved advance rate have been used in alluvium and basalt. The results of thermal analyses of some of these existing penetrators under conditions of constant advance rate in tuff, alluvium, and basalt are presented. The basic finite element heat conduction code (AYER) used in the calculations is briefly reviewed along with the methods of including radiation, temperature dependent material properties, and power generation. The internal temperature distribution, power requirements, and possible advance rates are determined for various consolidating and extruding penetrators. The effects of rock properties, penetrator configuration, and thermal limitations on the advance rate are considered. Heater designs and the use of heat pipes in specific designs are discussed. A comparison with experimental test data is made where possible.