Updating thermal head of RECoverable Autonomous Sonde (RECAS) for better drilling performance in Qilin Subglacial Lake exploration

Abstract. There are numerous subglacial lakes in Antarctica, typically covered by thick ice sheets. Qilin subglacial lake is one of the largest subglacial lakes in Antarctica, lying beneath approximately 3600 m of ice. The exploration of this unique environment is of considerable scientific importance. Recoverable Autonomous Sonde (RECAS) has been proposed for exploring Qilin subglacial lake. However, drilling into the lakes with such probe may be impeded by volcanic ash or small rock clasts within the ice sheet. In addition, RECAS is incapable of withstanding the extreme hydrostatic pressure existing in the Qilin subglacial lake. To address these challenges, the thermal head of RECAS was redesigned and fabricated. Compared with the original RECAS thermal head, the updated thermal head has extra water circulation unit. Laboratory test validated that the redesigned RECAS thermal head can operate at water pressures of up to 40 MPa. Moreover, its rate of penetration (ROP) improved by 21.1 % in clean ice, by 41.1 % in dust-laden ice, and by 253.4 % in ice with debris-rich ice. The updated RECAS thermal head is expected to be utilized to drill Qilin Subglacial Lake in the coming Antarctic work season.