the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 04 Aug 2026
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.
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Status: open (until 11 Sep 2026)
- RC1: 'Comment on egusphere-2026-4471', Anonymous Referee #1, 25 Aug 2026 reply
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The manuscript: Updating Thermal Head of Recoverable Autonomous Sonde (RECAS) for Better Drilling Performance in Qilin Subglacial Lake Exploration submitted by Li et al., reports on updates to an existing drilling instrument. The manuscript is well-written and generally easy to follow, also for a non-expert like me in this niche area. The English language is generally good, with only a few odd phrasings (that are still easy to understand).
The introduction is good and gives a nice overview of the field with adequate references for prior research. Obviously, this is an instrument paper with only a laboratory scale demonstration of the system, but the results presented are convincing. I have only some minor comments before I can recommend the manuscript is accepted.
Line 110: The manuscript would benefit from an improved description of the filters used to remove dust, i.e., what materials are used. Further is also not clear to me if the dust can risk clogging the filters or does the design make dust move into the internal cavity? The text states that dust is collected in this internal cavity. How big is this cavity and is there a risk of overfilling it during deep drilling? Please clarify this in the manuscript.
Line 113 (and also 409): “When drilling in dust-laden ice, the pump must be started”. How will the operator of the system in field conditions in Antarctica know that a layer of dust has been reached? Please clarify in the manuscript.
Equation 7: Shouldn’t the x have a double dot $\ddot{x}$ above to indicate second time derivative or a d2/dt2?
Equation 9: (similar to previous comment) Using a dot above z to indicate a unit vector is a little unusual notation as this is standard physics notation for a time derivative. I suggest using a hat $\hat{z} instead.
Line 152 and 187: I believe it is only necessary to mention “COMSOL Multiphysics 6.1” once.
Page 16. There are several expressions on this page, e.g. equations 17 and 19 for lambda, but it is not obvious where these expressions originate. I suggest adding a reference or two.
Line 305: There’s only a very short sentence on the supply voltage here, but I did not see a description of any electronic subsystems. I would assume that the unit contains a number of these. If so, it would be appropriate to have a description of these (or reference to previous papers with a description of these).
Line 359: The increase in rate of penetration is given as “approximately 21.8 %”. Based on the good, but somewhat “noisy” results in figures 12, 13, and 14 (which are all based on only a single experiment) the quoted increase seems to contain a bit too many digits. I believe it would be fairer to state 22 % or even round to 20 %.