Design and Performance of the Hotrod Melt-Tip Ice-Drilling System

Colgan, William; Shields, Christopher; Talalay, Paval; Fan, Xiaopeng; Lines, Austin P.; Elliott, Joshua; Rajaram, Harihar; Mankoff, Kenneth; Jensen, Morten; Backes, Mira; Liu, Yunchen; Wei, Xianzhe; Karlsson, Nanna B.; Spanggård, Henrik; Pedersen, Allan Ø.

doi:https://doi.org/10.5194/gi-2022-18

Preprints

https://doi.org/10.5194/gi-2022-18

Preprints

06 Oct 2022

| 06 Oct 2022

Status: a revised version of this preprint is currently under review for the journal GI.

Design and Performance of the Hotrod Melt-Tip Ice-Drilling System

William Colgan, Christopher Shields, Paval Talalay, Xiaopeng Fan, Austin P. Lines, Joshua Elliott, Harihar Rajaram, Kenneth Mankoff, Morten Jensen, Mira Backes, Yunchen Liu, Xianzhe Wei, Nanna B. Karlsson, Henrik Spanggård, and Allan Ø. Pedersen

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.

Received: 22 Sep 2022 – Discussion started: 06 Oct 2022

William Colgan et al.

Status: final response (author comments only)

RC1:
'Comment on gi-2022-18', Anonymous Referee #1, 04 Nov 2022

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.

References

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”, 101(15), 2654-2667.

Gillet, F. (1975), “Steam, Hot-Water and Electrical Thermal Drills for Temperate Glaciers”, 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”, 29, 24-40.

LaChapelle, E. (1963), “A Simple Thermal Ice Drill”, 4(35), 637-642.

Nizery, A. (1951), “Electrothermic Rig for the Boring of Glaciers”, 32(1), 66-72.

Rado, C., C. Girard, and J. Perrin (1987), “Electrochaude: A Self-Flushing Hot-Water Drilling Apparatus for Glaciers with Debris”, 33(114), 236-238.

Taylor, P.L. (1976), “Solid-Nose and Coring Thermal Drills for Temperate Ice”, pgs. 166-176 in J.F. Slpettstoesser, ed., University of Nebraska Press.

Citation: https://doi.org/10.5194/gi-2022-18-RC1
- AC1: 'Brief Reply on RC1', William Colgan, 10 Nov 2022
  
  I acknowledge that our lightweight hot-point drill is not fundamentally different from predecessors. However, the novel focus of this manuscript is on reproducibility and open hardware, something not done in other existing publications, and less on novel science results, which will be published elsewhere. Other groups have certainly drilled deeper with hot points, but our system description is the first to provide open-access computer-aided designs (CADs) of the melt tip and winch. This provides a previously unavailable level of engineering reproducibility, which is especially valuable for reducing barriers to new groups entering the sphere of melt-tip drilling.
  
  Citation: https://doi.org/10.5194/gi-2022-18-AC1
- AC2: 'Authors' reply to RC1', William Colgan, 28 Feb 2023
  
  We thank Reviewer 1 for their summary our melt-tip ice-drilling system and its testing. We do not state that our drilling system is fundamentally different from predecessor systems. However, as noted in our response to Reviewer 3, the 305 W/cm² specific power density of our system is approximately twice the maximum specific power density within the comprehensive survey of existing melt-tip drilling systems compiled by Talalay (2019). In a revised version of this manuscript, we will more explicitly contrast this specific power density from existing melt-tip systems. We will also more thoroughly cite the relevant historical literature that has been suggested by Reviewer 1.
  In a revised version of the manuscript, we will also provide better description of field test sites. This will include the coordinates and elevation of the D-11 ice-sheet borehole (76.4106°N, 68.2876°W, 528 m), as well as the coordinates and elevation of the lake boreholes (76.4124°N, 68.2949°W, 496 m). We will also specify the approximate Greenland borehole ice temperatures as being -10°C, based on ice temperatures observed during the drilling period at 8 m depth at the THU_L PROMICE automatic weather station located <1 km away (Fausto et al., 2021).
  We acknowledge that borehole diameter is an important parameter. Unfortunately, our melt-tip cannot measure borehole diameter, so we cannot provide further information on borehole diameter during testing beyond photography at the lake ice testing site. The boreholes in the artificial ice well were too recessed within the ice well to allow similar photography. The ice-sheet boreholes were obscured by ~1.5 m of snow cover, which similarly prevented measuring diameter from overhead photographs.
  While our manuscript does not present novel scientific findings, we feel that publishing an open-access design for our melt tip and ancillary elements falls within the scope of Geoscientific Instrumentation, Methods and Data Systems, as it allows other research groups to broadly benefit from our design and testing. For example, the Colgan et al. (2022) data repository associated with this manuscript contains, what we believe is the first open-access numerical code for borehole refreezing via a radial enthalpy solution. Novel scientific findings resulting from our melt-tip ice-drilling system will be published, in time.
  Colgan, W., Shields, C., Lines, A., Elliot, J., and Rajaram, H. Hotrod melt-tip ice-drilling system. https://doi.org/10.22008/FK2/DXXR06. GEUS Dataverse, V1. 2022.
  Fausto, R. S., van As, D., Mankoff, K. D., Vandecrux, B., Citterio, M., Ahlstrøm, A. P., Andersen, S. B., Colgan, W., Karlsson, N. B., Kjeldsen, K. K., Korsgaard, N. J., Larsen, S. H., Nielsen, S., Pedersen, A. Ø., Shields, C. L., Solgaard, A. M., and Box, J. E.: Programme for Monitoring of the Greenland Ice Sheet (PROMICE) automatic weather station data, Earth Syst. Sci. Data, 13, 3819–3845, https://doi.org/10.5194/essd-13-3819-2021, 2021.
  Talalay, P. Hot-Point Drills. In: Thermal Ice Drilling Technology. 1-80. Springer Geophysics. Springer. https://doi.org/10.1007/978-981-13-8848-4_1, 2019.
  
  Citation: https://doi.org/10.5194/gi-2022-18-AC2
RC2:
'Comment on gi-2022-18', Kris Zacny, 19 Dec 2022

Very informative and detailed paper. It's always great to see the new advancements!

Citation: https://doi.org/10.5194/gi-2022-18-RC2
- AC3: 'Authors' reply to RC2', William Colgan, 28 Feb 2023
  
  We thank Kris Zacny for summarizing our manuscript as informative and detailed.
  
  Citation: https://doi.org/10.5194/gi-2022-18-AC3
RC3:
'Comment on gi-2022-18', Anonymous Referee #3, 05 Feb 2023

This manuscript is a detailed technical description of a light weighted drill. I am very interested in the development of this type of electro thermal ice-drilling systems and new ideas within this area. I like that the authors are willing to share their development in an open-access repository.
My main critic is that I’m missing new concepts, ideas within the scope of this development and manuscript. Several electro thermal ice-drilling systems where developed and used over the last decades. The coauthor Pavel Talalay summarized several developments in his book “Thermal Ice Drilling Technology” (Springer, 2019). Please point out, what are the substantial new concepts, ideas, methods, or data within this manuscript.
In addition, I am still missing some smaller information on the design decisions and subsystem information. Please discuss how you calculated the values for your expected speed/penetration rate. Also, the specific power density of our melting tip is not included and discussed. In the Jilin laboratory test you recorded very detailed data and you present only mean values, without a discussion. For the description of the field tests I’m missing environmental parameters for the test in field, e.g. temperatures of the ice and the ice density.

Citation: https://doi.org/10.5194/gi-2022-18-RC3
- AC4: 'Authors' reply to RC3', William Colgan, 28 Feb 2023
  
  We thank Reviewer 3 for the value that they place on open-access design plans.
  In a revised version of the manuscript, we will more thoroughly compare our drilling system to similar existing systems. Briefly, aside from providing an open-access design, the main difference of our system is its relatively high power. With an idealized cross-sectional area of 19.6 cm² (equivalent to a circle of radius 2.5 cm) our drill provides a specific power density of 306 W/cm² at 6 kW power.
  Most melt-tip drills of similar cross-sectional area, especially those under development for extraterrestrial applications, are powered with a small fraction of this specific power density. Partly as a consequence of accommodating larger than normal power cables, our winch is substantially more robust, and well-documented, than in most previous systems.
  In a revised version of the manuscript, we will also better clarify how we calculate the expected rates of penetration shown in Figure 23. These expected rates of penetration are estimated from bivariate regression of the data compiled in Table 1.1 in Talalay (2019) for n = 29 melt tips, whereby penetration rate (R in m/hr) is a function of power (P in kW) and diameter (D in mm) following:
  R = 1.53*P – 0.15*D + 10.23
  This simple bivariate regression does not account for differences in heat transfer efficiency between systems or site-specific ice characteristics, but instead provides a first order estimate of the penetration rate associated with a given combination of melt-tip power and diameter.
  While the artificial ice well tests at Jilin University did record penetration rate each second, there was very little temporal variation around the mean penetration rate. For example, during the 45% power test shown below, the penetration rate was 5.9 ± 0.3 m/hr (between 25 and 150 cm depth; Figure R3-1). This was similar across all ice-well tests. We therefore only discuss the mean rate of penetration for each test. We will state this explicitly in the revised manuscript.
  Finally, with regards to the field site, we do not have measurements of ice density with depth at the drill site, but we can assume that the ablation zone ice has a bulk density, similar to that of pure ice. We can, however, add that ice temperature at the drill site was approximately -10°C, based on ice temperatures observed during the drilling period at 8 m depth at the THU_L PROMICE automatic weather station located <1 km away (Fausto et al., 2021).
  Figure R3-1 – Rate of penetration measured every 1 second during a 45% power test in the artificial ice well at Jilin University. Aside from initialization and cessation effects, the rate of penetration showed little temporal variance.
  Fausto, R. S., van As, D., Mankoff, K. D., Vandecrux, B., Citterio, M., Ahlstrøm, A. P., Andersen, S. B., Colgan, W., Karlsson, N. B., Kjeldsen, K. K., Korsgaard, N. J., Larsen, S. H., Nielsen, S., Pedersen, A. Ø., Shields, C. L., Solgaard, A. M., and Box, J. E.: Programme for Monitoring of the Greenland Ice Sheet (PROMICE) automatic weather station data, Earth Syst. Sci. Data, 13, 3819–3845, https://doi.org/10.5194/essd-13-3819-2021, 2021.
  Talalay, P. Hot-Point Drills. In: Thermal Ice Drilling Technology. 1-80. Springer Geophysics. Springer. https://doi.org/10.1007/978-981-13-8848-4_1, 2019.
  
  Citation: https://doi.org/10.5194/gi-2022-18-AC4
EC1:
'Comment on gi-2022-18', Andrew Wickert, 08 Feb 2023

At this point, we have three comments on this paper. The second and third might not be so substantial, but I believe that these, along with the first, suffice to proceed.
While I am not an expert on ice drilling, I am happy to see the organization of this paper and the content availabile from the associated repository to allow this work to be reproduced.
I encourage the authors to prepare and submit a revised manuscript draft.

Citation: https://doi.org/10.5194/gi-2022-18-EC1
- AC5: 'Authors' reply to EC1', William Colgan, 28 Feb 2023
  
  We thank the editor for inviting a revised version of our manuscript.
  
  Citation: https://doi.org/10.5194/gi-2022-18-AC5

William Colgan et al.

Data sets

Hotrod melt-tip ice-drilling system Colgan, W., C. Shields, A. Lines, J. Elliot and H. Rajaram https://doi.org/10.22008/FK2/DXXR06

William Colgan et al.

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Short summary

We describe a new drill for glaciers and ice sheets. Instead of drilling down into the ice via mechanical action, our drill melts its way down into the ice. Our goal is simply to pull a cable of temperature sensors on a one-way trip down to the ice-bed interface. Under laboratory conditions, our melt-tip drill has an efficiency of ~35% against a theoretical maximum penetration rate of ~12 m/hr. Under field condition, our efficiency is just ~15 %. Clearly room for improvement!


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