Numerical Study on Asteroid Deflection by Penetrating Explosion Based on Single-Material ALE Method and FE-SPH Adaptive Method

Round 1

Reviewer 1 Report

“Numerical study on asteroid deflection by penetrating explosion based on single-material ALE method and FE-SPH adaptive method” by Han et al. 

 

This manuscript describes a modelling approach to tackle the problem of asteroid deflection using penetrating explosions. The topic is of interest to the scientific community and appropriate for the journal. 

 

The authors start off by describing the importance of and the need for asteroid deflection in light of possible destructive impacts and the previously documented impacts. They then proceed to give an overview of modeling efforts and approaches currently in existence. The majority of the manuscript is dedicated to their simulations and results. 

 

However, there are serious deficiencies and flaws that must be addressed before the manuscript is considered for publication.

   

The manuscript is grossly under-referenced. There are many statements that are not backed up by citations which doesn’t do justice or service to the authors nor those whose work and accomplishments are being discussed here. There are also a lot of outdated references, as well as references inappropriate for the specific topic or selectively plucked to exclude some seminal works and to fit the authors’ narrative.  

 

The authors attempt to provide a “comprehensive” review but in addition to failing to appropriately reference sources, they also omit a lot of work that has been done to advance the field. This gives a false impression that their study is unique and strides ahead of other works, which simply is not true. 

 

I am not sure if this was done intentionally, or the authors haven’t done their due diligence when it comes to the literature review. There are too many instances to include in this review, but I will mention a few below. 

 

There are also a lot of critical gaps and omissions that are rather problematic and need to be addressed.  For example, the authors refer to various software packages and computational methods, but the citations are very sparce and not representative of the current state of the field. A more thorough review must be given, crediting earlier studies and providing context for previous work. 

 

It is my opinion that the manuscript requires major revisions in order to be considered for publication.  

 

Here are my comments on some representative examples of the shortcomings (again, please note that the instances are too numerous to be all included here): 

 

Line 32: The authors cite Borovicka (2013) in context of injuries and destructive potential of Chelyabinsk. That paper describes the orbital characteristics and is one of three primary papers published in Nature as a set. The more appropriate reference would be Popova et al. (2013) which focuses on the destructive effects and the aftermath, and Brown et al. (2013), which provides the energy estimate and the revised impact flux curve.  

 

Line 35: The authors need to include more citations here. 

 

Lines 39-40: This is a very generic statement, which does not provide any tangible information nor a citation. For example, what is considered fast enough response time?  

 

Line 43: How small is a “smaller” asteroid? 10s of meters, 100s, km size?  

 

Line 44: What is the required deflection velocity? Also, this entire paragraph has only 2 citations. 

 

Line 45: Please void using colloquial terms 

 

Lines 47-48: Reference? Also, what is considered short time? Days? Hours? Weeks? 

 

Lines 59-64: Citations? 

 

Lines 65-73: There are surely more than a single citation here. Also, some examples have to be given. Maybe I am missing something, but the authors mention rock blasting applications but omit impact applications. Also, there are models that do include the vacuum environment. Moreover, the authors mention iSALE and SALE later on (Line 109) but without any references or appropriate context.  

 

Line 67: Specify software packages used. These have limitations as well – if this approach is so ideal, how come it has not been implemented yet?  

 

Line 83: Which numerical model?  

 

Lines 88-125: There is not a single citation in this segment.  

 

Section 2: I might be missing something here, but the authors do not describe nor provide sufficient detail as to how was a single-material ALE method used to model different materials as shown later in the section (e.g., Fig. 1).  

 

Line 237 (also Line 281): What kind of material constants? What exactly do they represent? Are these unitless? While the answer might be intuitive for those familiar with the field, it is necessary to explain these so any reader can understand.  

Why are certain models selected over other models (e.g., damage)?  

 

Section 5: The assertion that this approach is better is not supported by solid evidence.  

 

Line 713: These seems to be some misinterpretation about the size scales here.

Author Response

see attached response-1#.

Author Response File: Author Response.docx

Reviewer 2 Report

   The paper explores the use of nuclear explosions to prevent asteroid impacts and models the process of deflecting hazardous asteroids using the single-material ALE and FE-SPH adaptive methods. It is well-organized, concise, and comprehensive, providing a clear discussion of the problem and its results. However, some areas require clarification before the paper can be accepted for publication.

1- Introduction: The authors discuss asteroid mitigation techniques, including kinetic impacts and nuclear explosions, with a focus on the advantages of using nuclear explosions. The introduction could be shortened, and the authors should address the following points to complete their discussion:

         (a) The authors suggest that nuclear explosions are the only option for deflecting asteroids when the warning time is short, but they do not provide any evidence or explanation to support this claim. This point needs clarification.
         (b) The text emphasizes the advantages of nuclear explosions over other methods but does not mention the potential political implications and risks and challenges associated with this method, such as the release of radioactive material into the atmosphere or the creation of space debris. This point should be addressed.
        (c)The difficulty of accurately predicting the trajectory and composition of asteroids, which is essential in determining the most effective mitigation strategy, needs to be discussed in the text.

2- Numerical simulation method: This section contains technical language that may be difficult for non-experts to understand. Some suggestions to improve the clarity of the text include:

           (a) While the text describes various numerical simulation methods for asteroid deflection, it does not provide a comprehensive evaluation of the strengths and weaknesses of each method. The authors discuss the ALE method and FE-SPH adaptive method but do not provide information on how these methods work or how they differ from other numerical simulation methods. This point needs clarification.
            (b) The authors mention that the asteroid is divided into elements, with a minimum side length of approximately 0.06m. The mechanism of this division is not clear. It would be helpful to explain how this is done and whether it is possible to estimate the maximum side length.
            (c) The text mentions several keywords without providing sufficient explanations or definitions. It assumes a high level of expertise and knowledge from the reader, which may not be the case. Providing more information on the specific models and methods used in the experiment, as well as the assumptions and limitations of the models, would improve the clarity of the technical details in this section.

Best regards, April 9, 2023

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Line 219: “All keywords are edited by LS-PrePost, the pre-processing software of LS-DYNA.” What does this mean?

Fig 2 looks like a screenshot. Is this taken from another book/paper or did the authors generate this themselves? If this is taken directly from another works, the authors need to obtain permission from the publisher directly to reproduce the figure.

Fig 6: Do authors have a high resolution version of the figure?

Fig 7: Please include time increments as well (also Fig 12).

Fig 8: (b) should say “cross-sectional view” (also Fig 11)

Author Response

Please see the attachment.

Author Response File: Author Response.docx