Ice drilling system with near-bottom hot water circulation

Ice drilling systems with near-bottom hot water circulation can be used for many challenging scientific tasks in the study of ice sheets, glaciers, and subglacial environments. These systems melt ice using water jets heated directly at the bottom of the hole, thus eliminating the use of long heavy hoses and surface pumps. To investigate the influence of the drill tip shape and nozzle diameter on the drilling process, a simplified laboratory prototype of the drill was designed and tested. The rated power of the downhole electric heater was 5.5 kW. A total of six melting tips in two groups were tested: three tips having a conical shape with different heights/angles and three parabolic tips with different focal parameters. In general, the conical tips provided a more stable drilling process. The experimental results showed that the rate of penetration (ROP) was highest when the specific load on the thermal tip was ~0.5 N cm−2 or 30% of the total drill prototype weight. The highest ROP of 2.5–3.1 m h−1was achieved with a nozzle diameter of 3.0 mm (at a flow rate of 3.0 L min−1). At the same time, the higher the flow rate, the faster the drilling speed was.