Design and Performance of the Hotrod Melt-Tip Ice-Drilling System
Abstract. We introduce the design and performance of a melt-tip ice-drilling system designed to insert a temperature sensor cable into ice. The melt tip is relatively simple and low cost, designed for a one-way trip to the ice-bed interface. The drilling system consists of a melt tip, umbilical cable, winch, interface, power supply, and support items. The melt tip and the winch are the most novel elements of the drilling system, and we make the hardware and electrical designs of these components available open access. Tests conducted in a laboratory ice well indicate that the melt tip has an electrical energy to forward melting heat transfer efficiency of ~35 % with a theoretical maximum penetration rate of ~12 m/hr at maximum 6.0 kW power. In contrast, ice-sheet testing suggests the melt tip has an analogous heat transfer efficiency of ~15 % with a theoretical maximum penetration rate of ~6 m/hr. We expect the efficiency gap between laboratory and field performance to decrease with increasing operator experience. Umbilical freeze-in due to borehole refreezing is the primary depth-limiting factor of the drilling system. Enthalpy-based borehole refreezing assessments predict refreezing below critical umbilical diameter in ~4 hours at -20 ˚C ice temperatures and ~20 hours at -2 ˚C. This corresponds to a theoretical depth limit of up to ~200 m, depending on firn thickness, ice temperature and operator experience.
William Colgan et al.
Status: final response (author comments only)
RC1: 'Comment on gi-2022-18', Anonymous Referee #1, 04 Nov 2022
- AC1: 'Brief Reply on RC1', William Colgan, 10 Nov 2022
- AC2: 'Authors' reply to RC1', William Colgan, 28 Feb 2023
RC2: 'Comment on gi-2022-18', Kris Zacny, 19 Dec 2022
- AC3: 'Authors' reply to RC2', William Colgan, 28 Feb 2023
RC3: 'Comment on gi-2022-18', Anonymous Referee #3, 05 Feb 2023
- AC4: 'Authors' reply to RC3', William Colgan, 28 Feb 2023
EC1: 'Comment on gi-2022-18', Andrew Wickert, 08 Feb 2023
- AC5: 'Authors' reply to EC1', William Colgan, 28 Feb 2023
William Colgan et al.
Hotrod melt-tip ice-drilling system https://doi.org/10.22008/FK2/DXXR06
William Colgan et al.
Viewed (geographical distribution)
This paper presents a very detailed account of design, together with very limited engineering data from laboratory and field tests, for a 2 m long, 5 cm diameter thermal ice drill intended to emplace thermistor strings vertically in ice sheets and glaciers. Electrical power (typically 1-6 kW) is supplied by a gasoline generator on the ice surface and conveyed to the drill via a tether paid out from the surface. The drill differs in various particulars (e.g., in using custom-made electrical cartridge heaters to try to direct heat preferentially along one axis), but is not fundamentally different in concept from many predecessors of similar size described in the literature.
The laboratory test data comprise 5-6 runs in pure ice at constant powers of 1.1-2.7 kW to depths of ~2 m in a 1 m diameter ice column at approximately -10 C (cf. pg. 12 and Fig. 2). Initial field tests are reported to “< 1 m” depth in lake ice near Thule Air Base in Greenland, ice temperature unspecified, at power levels 1.5-4.5 kW, with corresponding descent rates of 3-5.6 m/hr (Figure 2). A melt-hole diameter of 7 cm in the lake ice is reported (in apparent contrast to the laboratory cases). Two probe runs are also reported in an ice sheet ablation area near Thule at low but unspecified elevation, where ice was perhaps as thick as 44 m. No information on ice temperature, neither near-surface nor versus depth, is given. The first run reached 5 m depth over 3 hours using 3 kW of power, but was arrested by an accumulation of sediment at the bottom of the melt hole. The second run, initiated 2 m laterally distant from the first, reached 21 m depth over ~9 hours using 4.2 kW of power, before encountering a sediment layer which may have been detected independently by radar at that depth. There is no mention of melt-hole diameter in these latter two runs.
In the course of reviewing this paper, I re-read a number of literature accounts of lightweight thermal drilling efforts in the past, including Nizery (1951), LaChapelle (1963), Classen (1967), Gillet (1975), Taylor (1976), Rado et al. (1987), Kelley et al. (1994), and German et al. (2021) (none of which are referenced by the authors), as well as Dachwald et al. (2014), Zagorodnov et al. (2014) and Heinen et al. (2021) (which the authors do reference, albeit incorrectly in the case of Heinen et al.). These accounts all provide more detailed test results for ice penetration, to greater depths or (in the case of German et al.) with greater scientific return, than is the case in this paper.
I am therefore presently without a clear, compelling answer to the question of what scientific or engineering contribution this paper adds to the existing literature. (A detailed design alone for a probe not shown to offer any new capability does not qualify, in my view.) Neither is this question addressed in the paper so far as I can see. I would be open to an argument for what such a contribution could be, but absent such an argument at present, I am unable to recommend this paper for publication.
Classen, D.F. (1967), “Thermal Drilling and Deep Ice-Temperature Measurements on the Fox Glacier, Yukon”, M.S. Thesis, University of British Columbia.
German, L., J.A. Mikucki, S.A. Welch, K.A. Welch, A. Lutton and B. Dachwald (2021), “Validation of sampling antarctic subglacial hypersaline waters with an electrothermal ice melting probe (IceMole) for environmental analytical geochemistry”, International Journal of Environmental Analytical Chemistry 101(15), 2654-2667.
Gillet, F. (1975), “Steam, Hot-Water and Electrical Thermal Drills for Temperate Glaciers”, Journal of Glaciology 14(70), 171-179.
Kelley, J.J., K. Stanford, B. Koci, M. Wumkes, and V. Zagorodnov (1994), “Ice Coring and Drilling Technologies Developed by the Polar Ice Coring Office”, Memoirs of National Institute of Polar Research Special Issue 29, 24-40.
LaChapelle, E. (1963), “A Simple Thermal Ice Drill”, Journal of Glaciology 4(35), 637-642.
Nizery, A. (1951), “Electrothermic Rig for the Boring of Glaciers”, Eos Transactions of the American Geophysical Union 32(1), 66-72.
Rado, C., C. Girard, and J. Perrin (1987), “Electrochaude: A Self-Flushing Hot-Water Drilling Apparatus for Glaciers with Debris”, Journal of Glaciology 33(114), 236-238.
Taylor, P.L. (1976), “Solid-Nose and Coring Thermal Drills for Temperate Ice”, pgs. 166-176 in Ice Core Drilling, J.F. Slpettstoesser, ed., University of Nebraska Press.