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.

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.

We thank Kris Zacny for summarizing our manuscript as informative and detailed.

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.

We thank the editor for inviting a revised version of our manuscript.