The BAS hot water drill: development and current design

Over the past decade the British Antarctic Survey has developed a hot water drilling system that uses components easily carried by Twin Otter aircraft. The system has recently been upgraded and was successfully used in the 1990/91 and 91/92 field seasons to penetrate ice up to 562 m thick on Ronne Ice Shelf, Antarctica. Holes of at least 0.13 m in diameter were created and maintained. The hot water drill incorporates 300 kW of heating power with a water re-circulation system, removing the need for continuous snow melting while drilling. The drill nozzles have been designed to combat the problems of the rapid re-freezing of the water-filled hole. In the event of borehole closure above the nozzle, a less powerful but still effective drilling action is available upwards. A compressible mechanical valve system is incorporated which increases the back pressure when the operator is drilling too fast. This system ensures the nozzle is always freely suspended, resulting in a vertical hole. The work has allowed oceanographic measurements to be made in the sea-water underlying George VI Ice Shelf and Ronne Ice Shelf, Antarctica. The access holes have also been used for the installation of sensors in the ice and the ocean for long term temperature monitoring.