Lunar Cold Microtraps as Future Source of Raw Materials—Business and Technological Perspective
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsDear Authors,
This is very interesting and well-designed study, I would like to tank you for this scientific contribution and wish you good luck.
Author Response
The first reviewer had no comments regarding our manuscript. We would like to thank the reviewer for his time and appreciation of our manuscript.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors present a business report for obtaining resources from the Moon using the tool Lunar Quickmap. The authors make use of cold microtraps as the theoretical best places to look for resources.
Nonetheless, the paper looks more like an opinion piece or divulgative article rather than a rigorous technical paper of a scientific journal in some sections. The authors use vague, conditional, subjective or even wrong wording improper of a scientific publication. Examples of those are: "Existence of human civilization may be threatened by ongoing climate change", "We urgently need to find alternative low-emission energy sources.", "Local environmental conditions on various space objects will have a strong impact on chemical and physical processes, different from Earth's condition, which some space mining experts sometimes seem to forget about", "Elon Musk Plans to take humans to Mars" or "Thermonuclear reactors that use Helium-3 are (...) ecological and economically competitive relative to classic reactors", "But are there even better places to explore on the Moon? The answer is Yes".
Additionally, there are some clear errors, deep misunderstandings or wishful thinking of the authors that are also not acceptable in a scientific publication. Examples of those are:
1. The authors state that there is coal on the moon p7.L354.
2. The authors state that Helium-3 is a very valuable resource because of future Fusion Reactors, explaining that it is better than tritium. They then state that "Thermonuclear reactors that use Helium-3 will be small, compact, ecological highly effective and highly competitive relative to classic nuclear energy". This is way beyond the current scientific knowledge and belongs to the realm of science fiction, as fusion reactors are not even achieved at a commercial level, and D-T reactors are the theoretically best reactors according to Lawson's criterion.
3. The authors disregard asteroid mining as completely unfeasible, but on the other hand, Moon mining on permanent shadowed regions at 100 K appears to be easy. The justification given is definitely not satisfactory.
4. The three different scenarios used are not justified, specially on why the normal scenario is 5 cm.
Regarding the formatting of the article, the images taken from QuickMap are a simple screenshot not proper of a technical paper, no postprocessing has been done by the authors.
Regarding the research itself, it is straight forward, uncomplicated and up to some degree too simplistic. The research should be slightly deeper in the reviewer's opinion.
Acronyms and wording of helium must also be revised.
If the article is to be reviewed, the authors should pay special attention to all comments, and rewrite most sections that contains non-technical information.
NA
Author Response
I would like to thank the reviewer for the effort he put into writing the review. We have made every effort to take into account as many of the reviewer's comments as possible and respond to all of his remarks and comments as far as possible. Below are our answers.
REVIEWER: The authors present a business report for obtaining resources from the Moon using the tool Lunar Quickmap. The authors make use of cold microtraps as the theoretical best places to look for resources.
Nonetheless, the paper looks more like an opinion piece or divulgative article rather than a rigorous technical paper of a scientific journal in some sections. The authors use vague, conditional, subjective or even wrong wording improper of a scientific publication. Examples of those are: "Existence of human civilization may be threatened by ongoing climate change", "We urgently need to find alternative low-emission energy sources.", "Local environmental conditions on various space objects will have a strong impact on chemical and physical processes, different from Earth's condition, which some space mining experts sometimes seem to forget about", "Elon Musk Plans to take humans to Mars" or "Thermonuclear reactors that use Helium-3 are (...) ecological and economically competitive relative to classic reactors", "But are there even better places to explore on the Moon? The answer is Yes".
ANSWER: The article is an example of applied research. The authors wanted to present a broader context of their work, which has a strong social and business justification.
We can support most of the controversial theses mentioned here by the reviewer with solid scientific publications and business reports, which, however, would unnecessarily expand the text of the article with side threads - this is not a work aimed at proving climate theses or the superiority of specific energy sources.
However, this does not change the fact that these are theses/forecasts that may or may not come true.
We agreed to the reviewer's suggestion and most of the above-mentioned fragments were removed or edited.
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Sentence: “We urgently need to find alternative low-emission energy sources” has been changed on “There is pressure around the world to urgently find alternative low-emission sources.” By modifying this sentence, we wanted to remain in agreement with the other two reviewers, who did not indicate that this sentence should be removed, and at the same time meet the comments of Reviewer 2.
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Sentence: “Local environmental conditions on various space objects will have a strong impact on chemical and physical processes, different from Earth's condition, which some space mining experts sometimes seem to forget about.” This sentence is an important note for readers who want to implement projects in space. Of course, the laws of chemistry and physics in the universe are identical, and at least according to the current state of knowledge, nothing indicates otherwise. However, local physical conditions may influence the course of many chemical processes, including industrial processes. An example here is the electrolysis reaction, the effectiveness of which depends on the value of the gravitational force. Information on this subject can be found in the publication:
https://www.nature.com/articles/s41467-022-28147-5
However, we agree with the reviewer that the final part of the sentence contains our opinion, which can be omitted. Therefore, we replaced the above sentence with a shorter sentence: “Local environmental conditions on various space objects will have a strong impact on chemical and physical processes, different from Earth's condition.”
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Sentence: "The Starship vehicle, which Elon Musk plans to take humans to Mars and enable its settlement, is still being tested and has not yet reached low Earth orbit (LEO) at the time of writing this article"
we change on
“Elon Musk is conducting R&D work aimed at developing a Starship space vehicle that will enable the colonization of Mars. Starship is still being tested and has not yet reached low Earth orbit (LEO) at the time of writing this article”
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Sentence: “Thermonuclear reactors built to operate on the basis of 3He fuel will be small, compact, ecological, highly effective and highly competitive with classic nuclear energy” was left in text.
This sentence is correct. The advantage of thermonuclear fuels based on the D + 3He and 3He + 3He reactions will be that they do not produce neutrons (aneutronic reactions).
Already in the classical energy industry based on fissile materials, the emitted neutrons cause the destruction of reactor materials and the formation of secondary radioactive elements.
In the case of fusion reactors, the neutron flux is expected to be several orders of magnitude higher, which will result in faster degradation of materials. It is expected that every few years it will be necessary to renovate the fusion reactor casings, which will affect the economics of such a reactor. It can be expected that information about the generation of radioactive elements will raise dissatisfaction among environmental groups.
Moreover, reactors based on the D + 3He and 3He + 3He reactions produce charged particles - protons. These reactors will not have to use gas turbines to generate electricity, which will significantly increase their efficiency. Therefore, the statements presented in the sentence are highly justified, although they are still rather predictions of thermonuclear fusion specialists.
The disadvantage of the D + 3He and 3He + 3He thermonuclear reactions is that they require a higher ignition temperature than the D + T and D + D reactions.
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Sentence: “But are there even better places to explore on the Moon? The answer to this question is yes” was changed on “Are there places on the Moon with a higher concentration of raw materials that could be more profitable to exploit? The answer to this question is positive”.
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REVIEWER: Additionally, there are some clear errors, deep misunderstandings or wishful thinking of the authors that are also not acceptable in a scientific publication. Examples of those are:
- The authors state that there is coal on the moon p7.L354.
ANSWER: This is an obvious translation error, because instead of "coal" it should be "carbon". I would like to thank the reviewer for catching this mistake, because it would be a significant mistake, because of course there are no hard coal or brown coal deposits on the moon, which is what the word "coal" would suggest. In total, we identified 5 places in the text where the word "coal" was incorrectly used instead of the word "carbon". Corrections have been made in all places.
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REVIEWER:
- The authors state that Helium-3 is a very valuable resource because of future Fusion Reactors, explaining that it is better than tritium. They then state that "Thermonuclear reactors that use Helium-3 will be small, compact, ecological highly effective and highly competitive relative to classic nuclear energy". This is way beyond the current scientific knowledge and belongs to the realm of science fiction, as fusion reactors are not even achieved at a commercial level, and D-T reactors are the theoretically best reactors according to Lawson's criterion.
ANSWER: Helium-3 is already a highly valuable raw material. A few years ago, 1 kg of this isotope was valued at approximately 16.6 M$. The high price is caused by the high demand for this isotope in relation to its supply. It is also a strategic raw material.
Fusion reactors that will be based on the D + T reaction have the advantage that it is a reaction with a relatively lowest ignition temperature. If the first commercially operational fusion reactor is built, it will most likely use D + T or D + D fuel, although the D + D fusion requires a higher ignition temperature.
However, this is where the advantage of the D + T reaction ends. This reaction will generate neutrons that will damage the materials in the reactor shields. Experts predict that this will require a major overhaul of such reactors every few years. This will increase the costs of using such reactors. The emitted neutrons will also cause the formation of secondary radioisotopes, which will certainly raise objections from ecologists in the future.
Future fusion reactors based on D + 3He or 3He + 3He reactions will avoid the problems described, because these reactions do not generate neutrons. Moreover, the reactions produce charged particles - protons, and according to experts, it will be possible to produce electricity without the need to use gas turbines and classic liquid circulation, which will contribute to increasing the efficiency of such reactors. This is the reason why specialists predict that thermonuclear reactors based on D + 3He or 3He + 3He reactions will be small, compact, ecological and highly competitive with classical energy.
An example of a startup using helium-3 in its thermonuclear fusion technology is Helion Energy (https://www.helionenergy.com/). The specific design and technology of the reactor used by this company makes it possible to overcome technological problems resulting from a high ignition temperature (than for the D + T reaction). A detailed description of this technology can be found on the Helion Energy website.
Moreover, Helium-3 can be used in first-generation fuels as a starter for thermonuclear fusion reactions, because just 1% addition of Helium-3 increases the energy of ions up to 10 times. Source:
https://news.mit.edu/2017/mit-plasma-research-collaboration-gives-fusion-heating-boost-0821
A detailed discussion on the advantages of D+He-3 fuel over D+T fuel and on which conditions it occurs can be found in the publication below:
https://link.springer.com/article/10.1007/s10894-023-00367-7
This publication reference was added to manuscript.
Tritium is an even more expensive raw material than helium-3 and is difficult to produce. Although in thermonuclear reactors using D + T fuel it is planned to use the so-called lithium blankets that will produce tritium, but this is an ineffective process - at least according to the current state of technology. What's worse, the half-life of tritium is 12.33 years. This means that after more than 12 years, only 50% of the atoms of this isotope will be present in a tank containing tritium. Therefore, long-term storage of this raw material is not possible, which disqualifies its use as a potential energy reserve.
However, we agree with the reviewer that despite the enormous progress in the field of thermonuclear fusion in recent years, the work on this issue by many startups from around the world (some of them can be found on the website of the Fusion Industry Association), the financing of some of them by large corporations ( e.g. Microsoft, Chevron, Eni) thermonuclear fusion is still a S-F topic because there is still no industrial and business Proof-of-Concept (PoC). However, there are rational premises that helium-3 will be the strategic raw material of the future and this fact cannot be ignored in scientific, technical and economic analyses.
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REVIEWER:
- The authors disregard asteroid mining as completely unfeasible, but on the other hand, Moon mining on permanent shadowed regions at 100 K appears to be easy. The justification given is definitely not satisfactory.
ANSWER: We do not claim in the article that the extraction of raw materials in permanently shaded areas will be technologically easy. We also do not claim that mining raw materials on asteroids is technologically impossible. We argue that for potential investors, the exploitation of asteroids is burdened with a much higher investment and technological risk than the exploitation of raw materials, even in the most difficult-to-reach places on the Moon, and we have provided a justification why this is so. Moreover, we identified cold microtraps (which range from a few centimeters to several kilometers in diameter) as areas that were easier to exploit than the perpetually shadowed areas in large craters.
According to the current state of knowledge, asteroids have the greatest raw material potential compared to the Moon and Mars. However, in the case of a flight to Mars, we must wait for the launch window, which occurs once every two years, when the alignment of the planets Earth and Mars is most optimal for such a journey. It will be similar with asteroids found in the asteroid belt between Mars and Jupiter, but the distance to them is greater than to Mars.
This increases the time it takes to complete subsequent engineering iterations of the asteroid exploration equipment. It is unlikely that the first version of such a device will work fully correctly, and not all conditions can be predicted and modeled in the laboratory or on a computer. Final verification of the equipment's operation is only possible in real space mission conditions. The extracted raw materials must also be returned to Earth. As a result, the time from launching the project to its monetization will probably be many times longer than in the case of exploiting raw materials on the Moon.
The delay time of the signal between the Earth and the asteroids is so large that it is not possible to remotely control asteroid exploration devices in real time. This means that they must have a high degree of autonomy, which is difficult to achieve. Automation of the drilling process is particularly difficult due to many possible failures and drilling complications, as well as the lack of full knowledge of the geomechanical parameters of the drilled asteroids.
An additional difficulty is microgravity, which prevents the use of mining and drilling solutions known from Earth, which require gravity to operate. A small amount of pressure applied to an asteroid can cause the device to move away from the asteroid and into space. To prevent this from happening, you need to anchor yourself to the asteroid, which may be difficult.
Therefore, for many potential investors, the exploitation of asteroids with a long investment return horizon and high technological risk will be unattractive from a business perspective. This is the reason why we stated in the article that asteroid exploitation is difficult, but not technologically impossible. Exploiting raw materials on the Moon is much easier, but that doesn't mean it doesn't pose technological challenges.
NASA is currently working on new types of nuclear drives that could shorten the time it takes to get to asteroids. If such drives were created, it would be a game changer that could facilitate the exploitation of asteroids.
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REVIEWER:
- The three different scenarios used are not justified, specially on why the normal scenario is 5 cm.
ANSWER: Although the Moon has been explored by many missions, most of the data is scientific, not industrial. The thickness of various types of deposits is unknown, including the analyzed CO2 deposits. Data obtained from sampling during the Apollo mission cannot be generalized to the locations of deposits - especially since they are located in subpolar zones not explored by astronauts during the Apollo mission. There is a lack of in-situ measurements of deposits sites, especially geological data from drilling. This results in high inaccuracy in estimates of the size of deposits on the Moon. Deposits on the Moon detected using remote satellite methods should be classified as probable deposits, which obviously affects their valuation.
The adopted scenarios were defined arbitrarily, which is emphasized in the text, because we do not have accurate data on the thickness of the layer containing CO2. It is assumed here that most of the carbon may come from the solar wind, although its sources may also be other, e.g. from carbonaceous asteroids. Particles of solar wind and cosmic radiation can reach several dozen centimeters deep into the regolith, hence the three scenarios adopted: pessimistic - 1 cm, nominal - 5 cm and optimistic - 1 meter. Of course, this is a significant simplification (does not take into account, for example, the continuous deposit and mixing of material by the falls of micrometeorites over millions of years), and the thickness of the layer containing CO2 may be much greater. However, when performing the analysis, attempts were made to make highly conservative assumptions to increase the probability that the deposits are underestimated rather than overestimated.
We understand that this methodology is not ideal from a scientific perspective. However, without accurate drilling data and in-situ measurements, it is not possible to determine the thickness of the carbon-bearing layer with 100% certainty. We want our scientific article to trigger a scientific discussion, so that in the near future there will be articles presenting more accurate quantitative and economic estimates.
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REVIEWER: Regarding the formatting of the article, the images taken from QuickMap are a simple screenshot not proper of a technical paper, no postprocessing has been done by the authors.
ANSWER: We agree with the reviewers' concerns that Figures 2 - 23 did not make a significant scientific contribution. However, it should be remembered that the article is written with not only a scientific audience in mind, but also practitioners who are professionally (business-wise) searching for space deposits. Hence, we wanted to show what it was like to work with the Lunar Quick Map tool. Unfortunately, it is not possible to obtain photos in a higher resolution, because they are print screens from Lunar QuickMap. Even if such a print screen is made on a high-resolution monitor, many markings will not be legible when placed in the text of the article. Therefore, we decided to accept the reviewers' comments and remove Figures 2 to 23. However, we kindly please leave Figure 1
We also removed Tables 1 and 2, because the results from these tables are repeated in Table 3. These changes resulted in the need to renumber the table numbers.
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REVIWER: Acronyms and wording of helium must also be revised.
ANSWER: Helium found in nature consists of two isotopes - helium-4 and helium-3. The ratio of He-3 to He-4 isotopes in the solar wind is 1:10,000. The price of the Helium-3 isotope is about $16.6 M/kg, and the price of ordinary helium is only 30-70 $/kg. The authors emphasize that they are writing about the helium-3 isotope, and the designations used are commonly used in physics publications. Using the single word helium will be highly misleading..
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REVIEWER: If the article is to be reviewed, the authors should pay special attention to all comments, and rewrite most sections that contains non-technical information.
ANSWER: We have made every effort to incorporate corrections suggested by all three reviewers wherever possible.
Reviewer 3 Report
Comments and Suggestions for AuthorsDear authors,
This manuscript has an interesting idea for readers, but there are several major problems.
The abstract is very dumb and unscientific.
Referencing is extremely bad. Please reference the manuscript part by part and use up-to-date references.
Content should be summarized.
The text of the article is fluent and good, but it needs serious summarization. Figures and tables should be integrated.
The conclusion should be rewritten.
I did not understand exactly what specific research the authors have done and I think a review paper was written from available data and articles and websites.
Anyway, revise and apply my comments in PDF's file.
Best Wishes
Comments for author File: 
Comments.pdf
Minor editing of English language required
Author Response
We would like to thank the reviewer sincerely, of all the reviewers, he put in the most effort and sent us the text with his remarks and comments. We were even more pleased to make every effort to take into account as many of the reviewer's comments as possible wherever possible.
Please remember, however, that in addition to its scientific value, the article should also have practical value. We address the article not only to scientists, but also to practitioners involved in the search for space resources professionally (in business). We also want to start discussions on the estimation and economic evaluation of carbon resources - we hope that our article will be followed by publications with an even better methodology for estimating the business potential of carbon resources on the Moon.
Below are our answers and the list of changes:
REVIEWER: Dear authors,
This manuscript has an interesting idea for readers, but there are several major problems. The abstract is very dumb and unscientific.
ANSWER: Following the reviewer's suggestions, we rewrote the abstract.
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REVIEWER: Referencing is extremely bad. Please reference the manuscript part by part and use up-to-date references.
Mostly done
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REVIEWER: Content should be summarized.
The conclusion should be rewritten.
The text of the article is fluent and good, but it needs serious summarization. Figures and tables should be integrated.
I did not understand exactly what specific research the authors have done and I think a review paper was written from available data and articles and websites.
Anyway, revise and apply my comments in PDF's file.
ANSWER: Following the reviewer's suggestions, we have made changes wherever possible.
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LIST OF CHANGES ACCORDING TO REVIEWER WISH (line number is line number from orginal manuscript commented by reviwer):
Keywords
Increased and refined keywords as requested by reviewer 3.
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There are concerns that the further development and existence of human civilization may be threatened by ongoing climate change
Sentence removed - Reviewer 2 found it to be an unnecessary opinion and inappropriate for scientific texts.
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Line 27 and 28 – as requested “rare earth elements” and “platinium group elements” changed to Capital Letters “Rare Earth Elements” and “Platinium Group Elements”
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Line 27 - according to the reviewer's suggestion, REE producing countries and a literature reference were added. This resulted in the need to renumber the literature references in the text.
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Line 29 – Sentence “Therefore, first of all, it is necessary to select and focus on deposits on the Moon that will be easily accessible and with the lowest possible technological and investment risk.” was removed. This is our opinion even though it is justified for practical reasons.
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Line 32 – word “visionaries” removes as requested by reviewer.
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Line 37 – “The website” replaced by “The Asterank online database”. A short description of this database has been added: "This is a scientific and economic database of over 600,000 asteroids"
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Line 38 – the publication number was corrected and literature references were renumbered in the rest of the text - in accordance with the reviewer's request
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Line 41 – Sentence: “There are no in-situ measurements on asteroids that could clearly confirm their raw material potential” was removed. This statement is correct because past space missions to asteroids were mainly scientific and focused on collecting surface materials, mainly debris. To confirm the raw material potential, deeper samples should be taken to determine what is beneath the surface layer. However, this statement may incorrectly suggest that there have been no missions to asteroids, which made this reviewer doubtful.
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Line 44 – Sentence “However, in the case of some asteroids, the predicted market values of the raw materials they contain are so high that even an estimation error of 3 orders of magnitude (or more) means that their exploitation may still be profitable.” was removed. This statement is correct, but it is a private opinion that we are unable to support with publication. We agreed with the reviewer's comments and removed this sentence.
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Line 50 – “This does not mean, of course, that each of them will work in space” changed on “Not all of them will work in space”
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Line 52 – “the course of missions in space, analyze geological data,” removed.
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Line 55 – The sentence “Examples of such devices that require gravity to function properly include wheeled vehicles, excavators, bulldozers, drilling and impact devices, gravity separators, conveyors transporting excavated material, and robot arms. The lack of gravity changes the dynamics of these devices, often making it difficult for them to function correctly or effectively.” was added in accordance with the reviewer's comment and suggestion to mention such devices and explain why gravity force is important.
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Line 58 – The sentence “For example, during the normal process of drilling oil and gas wells on Earth, many potential failures and drilling complications can occur” was changed on:
“For example, during drilling typical borehole in oil and gas industry wells on Earth, many potential failures and drilling complications can occur [4, 5] and some of them can occur also during drilling in space objects like planets and asteroids”.
to be more clear and were added references according to reviewer request.
Because two additional reference sources were added at the reviewer's request, the references in the text were renumbered.
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Line 65 – “For example, a trip to Mars takes 7-9 months and requires waiting for the launch window, which appears once every two years. Asteroids rich in raw materials are much further away” was changed on:
“For example, a trip to Mars takes minimum 7 [8] months and requires waiting for the launch window, which appears once every two years. Asteroids rich in raw materials are much further away”
to be more clear and were added references according to reviewer request.
Because two additional reference sources were added at the reviewer's request, the references in the text were renumbered.
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Line 68: Sentence: “There are many factors that cannot be predicted and modeled on Earth. Probably only the second or third version of the device will work properly” according to reviewer doubts – it was our opinion but justified.
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Line 70: Sentence: “This extends the time horizon for returns on investments from space mining operations on asteroids to 10 years or longer. Considering the high risk of mission failure, this is un-acceptable to most investors. There are NEOs (Near Earth Objects) - asteroids that are closer to the Earth, but they still suffer from the same technical problems as for more dis-tant asteroids. Until humanity invents faster space drives, the exploitation of asteroids on an industrial scale will not be possible.”
About the fragment: “This extends the time horizon for returns on investments from space mining operations on asteroids to 10 years or longer. Considering the high risk of mission failure, this is un-acceptable to most investors.” was changed on “This extends the time horizon for returns on investments from space mining operations on asteroids to 10 years or longer. Considering the high risk of mission failure, this could be unacceptable to most investors.” - we cannot provide a bibliography because it is our business conclusion based on the available information, which has been justified here. I would suggest leaving it in the text.
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Line 88: “low Earth orbit (LEO)” changed on “Low Earth Orbit (LEO)”
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Line 102: “The flight time to the Moon is 4 - 7 days” was changed on “The flight time to the Moon takes about 3 days [13]” – in previous time value was mistake and we add reference as requested reviewer.
Line 105: “The delay time of the Earth-Moon signal is only 1.28 seconds” was changed on “The delay time of the Earth-Moon signal (propagation time to the Moon and back) ranges from 2.4 to 2.7 seconds, with an average of 2.56 seconds (the average distance from Earth to the Moon is 384,400 km)”
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Line 107: In sentence: “The lunar environment is also well known to us, we have been there, there is a lot of data from past space missions, and the future presence of people on the Moon in connection with the Artemis program gives in some locations a chance for astronauts to intervene if any problems with the equipment occur.” Was added reference:
“The lunar environment is also well known to us, we have been there, there is a lot of data from past space missions [16], and the future presence of people on the Moon in connection with the Artemis program gives in some locations a chance for astronauts to intervene if any problems with the equipment occur.”
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Line 126: Sentence “However, currently available data obtained by remote methods (satellite imaging) can significantly narrow the area of further searches, enabling the selection of the most prospective places for future industrial mining space missions” changed on “However, currently available data obtained by remote methods (e.g. spectroscopic measurements, neutron spectroscopy, SAR imaging, gravitometry, magnetometry) (lunar mission e.g. : Chang’e 1, Chandrayaan-2, Grail A, Grail B, Lunar Reconnaissance Orbiter, LCROSS, Korea Pathfinder Lunar Orbiter (Danuri)) can significantly narrow the area of further searches, enabling the selection of the most prospective places for future industrial mining space missions” (added names of methods and lunar mission examples according to reviewer wish).
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Line 171: Sentence added “Two factors are important for the formation of resources in craters resulting from meteorite falls: what percentage of the impactor (whose fall formed the crater) will be thrown irreversibly into space and what concentration of individual raw materials the impactor has.” according to reviewer wish to make short introduction.
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Line 198: Sentence added “A detailed discussion on the advantages of D + 3He fuel over D + T fuel can be found in the publication [20].” This is in response to comments from reviewer 2 who had doubts as to whether the He-3 based fuel was superior to the D+T fuel. The literature reference makes this clear.
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Line 476: We agree with the reviewer that a detailed FlowChart would be helpful. However, describing how to select economically effective deposits on the Moon is highly complex knowledge. The FlowChart would have to be highly complex and its preparation would be extremely time-consuming. In fact, such a FlowChart itself would be material for a separate article, which the authors will consider creating in the future. In turn, introducing a simplified FlowChart will not add anything valuable to the article and will only be an artificial creation in the article without any scientific value.
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Line 548: Please leave this photo as an illustration of what the Lunar QuickMap tool looks like. The article is intended to be used not only by scientists, but also by practitioners who professionally (in business) are engaged in the search for space raw materials. Unfortunately, it is not possible to obtain a photo in a higher resolution.
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Line 566: We suggest leaving the text in the form of points. The introduction of a table without parameter values here was artificial and strange to the readers of the article.
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Line 586: The sentence „The groundbreaking work of Chinese researchers [17] on helium bubbles was published in June 2022 and reached us when the work was already being carried out, hence the analyzes did not take into account the possibility of the occurrence of this type of deposits.” This is our statement of fact and there are no references to it.
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Line 597 – 664: We agree with the reviewers' concerns that Figures 2 - 23 did not make a significant scientific contribution. However, it should be remembered that the article is written with not only a scientific audience in mind, but also practitioners who are professionally (business-wise) searching for space deposits. Hence, we wanted to show what it was like to work with the Lunar Quick Map tool. Unfortunately, it is not possible to obtain photos in a higher resolution, because they are print screens from Lunar QuickMap. Even if such a print screen is made on a high-resolution monitor, many markings will not be legible when placed in the text of the article. Therefore, we decided to accept the reviewers' comments and remove Figures 2 to 23.
We also removed Tables 1 and 2, because the results from these tables are repeated in Table 3. These changes resulted in the need to renumber the table numbers.
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Line 751: One of the reviewers asked that Tables 9 - 10 (currently numbers 6 - 8) be combined into one table. However, we suggest leaving three separate tables for each of the three cases. Combining these tables into one table will result in one large table in which the information contained will not be presented in a readable way for the reader. Moreover, it would require creating a table format that would deviate from the guidelines for the authors of the text, which we wanted to avoid.
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors have improved the paper based on the previous reccommendations. The authors have modified the tone of the paper in a sense that it does not look like an opinion piece anymore, but it resembles now an actual scientific paper.
There is still discrepancy for what the authors consider "the future" and the reviewer considers "wishful thinking" or mere speculation without a solid basis. Example of these are statements such as "Thermonuclear reactors built to operate on the basis of 3He fuel will be small, compact, ecological, highly effective and highly competitive with classic nuclear energy" undermine the credibility of the work.
The justification the authors provide in the rebuttal for the selection of 5 cm as the base case is not satisfactory to the reviewer.
Nonetheless, the paper is extensive and agglomerates many of the current knowledge around Moon Mining, which makes it a useful paper for the research community. The reviewer assumes that given that this review occurs in mdpi, there will be not a second review eventhough some of the concerns are not correctly addressed in the reviewer's opinion.
NA
Author Response
We would like to thank reviewer 2 again for his efforts in completing the review.
Reviewer 3 Report
Comments and Suggestions for AuthorsDear authors
I can't find my comments answers in manuscript.
The manuscript quality extremely bad now
Previous version is better than this.
I think this manuscript should be rejected.
We are trying to make manuscript better but you don't upgrade this manuscript!
Author Response
We would like to thank reviewer 3 again for the detailed list of suggested improvements that reviewer 3 compiled in the first round of review. We agreed with most of these corrections and we appreciate the work done by reviewer 3 even more. However, we ask reviewer 3 to re-examine our response, as most of his suggestions have been taken into account and incorporated into the text.
Reviewer 3 writes "The manuscript quality extremely bad now ..." and "Previous version is better than this ...". This is unlikely given that:
1) most of the corrections suggested by the reviewer were accurate and correct,
2) the reviewer wrote in the comments to the text in detail what corrections he expects,
3) these corrections were mostly implemented - a total of about 30 corrections were made in accordance with the reviewer's requests.
These statements (made by reviewer 3) also contradict the opinion of reviewer 2, who stated that the text is better on the scientific side compared to the previous version, which is largely due to the corrections made in accordance with the suggestions of reviewer 3.
Please note that a detailed list of corrections can be found in the Cover Letter included in response to the first round of reviews as an additional file. Please note that the line numbers of corrections listed in this document correspond to the line numbers in the PDF document containing reviewer 3's comments on the original text. The vast majority of fixes are in line with reviewer 3's suggestions in his comments.
Reviewer 3 writes "I think this manuscript should be rejected." This is a surprising position, because in his first opinion, reviewer 3 did not formulate such an extreme conclusion. If most of the detailed guidelines of reviewer 3 have been taken into account, it is logical that the text cannot be worse but must be even better. Moreover, this position is an extreme opinion considering that the opinions of reviewer 1 and reviewer 2 are positive.
Moreover, the selection of the bibliography was not accidental, but deeply considered. The bibliography contains links to the latest, top and valuable articles related to space resources, which constitute approximately 62% of the bibliography. The remaining 38% are references to equally valuable materials related to space resources contained on websites. It should be emphasized that these are mostly websites of recognized industry portals, space agencies, companies from the New Space sector, and there can be no doubts about their credibility and scientific reliability.
None of the other reviewers commented on the selection of the bibliography, and even reviewer 2 stated "the paper is extensive and agglomerates many of current knowledge around Moon Mining which makes it a useful paper for research community...". Therefore, we believe that the current bibliography is optimal and there is no justification for further improvement.
Reviewer 3 writes “We are trying to make a manuscript better but you don’t desire this manuscript!” As we have shown, we made about 30 corrections requested by reviewer 3. We believe that there was a little confusion because:
1) it is not possible to attach an additional file for the reviewer 3 with a list of changes made (there is such a possibility in the second round, we didn't see it in the first round),
2) attaching the manuscript with track changes mode
may have made it difficult for reviewer 3 to read all the changes made, which may have been the reason why reviewer 3 stated “I can’t find my comments answers in the manuscript.” Please also take into account that we only received reviewer 3's comments in a PDF file, not an editable WORD version.
We hope that our answers will satisfy reviewer 3. We would like to thank him once again for the great effort he put into preparing the review and the list of detailed corrections along with comments. Thanks to reviewer 3, our text has become much better.
In this round, we have included a Cover Letter for "reviewer 3", and we have also attached the manuscript with all changes accepted, which should make it easier for recent reviewer 3 to familiarize themselves with all the changes that were introduced after the first round. We apologize again for the confusion and additional work for reviewer 3. Thank you again for your time.
Author Response File: Author Response.pdf
