Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Review :

 

1. The authors limited the model to symmetric and claimed that the equivalent M and D matrices are diagonal.

- First of all, I do not believe that a symmetric truss has diagonal M and D equivalent matrices. When a continuous structure is discretized into lumped components, there are always coupled elements regardless of the symmetricity. The authors need to verify this claim.  

- In the event of diagonal M and D matrices for this symmetric truss structure, I would ask the authors to apply the equivalent to an unsymmetric example where there are coupled components of the matrices, and validate the accuracy of the method on the discrepancy ratios. Then adjust the conclusion accordingly.

 

2. The equivalent method still discretizes the structure into elements, which is very similar to the FEM method. The authors claim that the FEM’s efficiency is low and that the equivalent method is more suitable for dynamic model of space column structure.

- With today computer high performance, there is no efficiency limit with the FEM method. I do not agree with the authors comment and argument.

- In this particular application, the error of the equivalent method is still at 4.7%, which is significant for space structures where the accuracy is tremendous for the safety and reliability of billion-dollar space exploration simulation projects. Do you think the manager of the project will agree to use the equivalent method on the project? Me I don’t.

 

3. In the revised model section by dynamic, it seems that the frequency tunning is great with max error 4.7%.

- However, I do not see a matching of the mode shapes, especially at torsional modes. For example, the mode d) in equivalent model look more similar to the mode b) in FEM. Mode f) equivalent looks more like mode d) in FEM.

 

     

 

 

Author Response

‘Responses to Reviwer 1.docx' is uploaded.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

In this paper, the authors presented the dynamics of a space in–orbit service simulation experiment platform with suspension rope and column quadrilateral truss structure as connecting devices. They compared and examined the equivalent beam model and column quadrilateral truss structure’s natural vibration characteristics and validated the model via numerical analysis.

My comments are as follows:

1.      As government space agencies and private space companies are gearing up to send humans and cargo to deep space, that is the Moon, Mars, and beyond, effects of the extreme space environments, such as cosmic radiation and temperature, on the spacecraft are of great concern. Based on the numerical results obtained, how will your results be able to convince the space companies that the dynamic model of the space in–orbit service simulation test platform established will be able to withstand the extreme space environment? Please, include it in the manuscript.

2.      For better understanding by the interested readers, please supply the reference of Eq. 1.

3.   On page 14 it was stated that one of the reasons for having relatively large frequency relative errors was that “when calculating the periodic element elastic potential energy, the strain on the neutral axis of the periodic element is regarded as a constant”. What is the rationale behind regarding it as a constant and if it is regarded as a variable what will be the effect? Include your description in the manuscript.

4.      For your numerical analysis and simulations, state the software package that was used.

 

 

Author Response

'Responses to Reviwer 2.docx' is uploaded.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

An interesting paper entitled “Equivalent Continuum Modeling for Flexible Slender Quadrilateral Truss Structure.”

The abstract contains appreciably explained research problem and methodology. No compelling quantitative and qualitative performance metrics are presented. The authors should revise it to capture the relevant space-grade research findings.

The literature review is appreciable but should be improved/to accommodate the associated with the spatial data streams of the spacecraft system engineering design process and/or class of design contingencies / margins.

Please, correct the typos and/or grammatical errors e.g., “… theirs cost and launch cost …;” “… kinetic energy is solved. through the energy …” and “Compared to with ….” Did you mean “Taylor expansion” on page 19?

The paper would benefit from a delineation of how the proposed large-scale spacecraft structure modelling technique and/or ground in-orbit service test platform methodology impacts the conceptual and the mission design objectives.

The performance metrics of the proposed space QTS model are compelling. The mathematical and the system models are judiciously accomplished.

Please, define all acronyms at first mention. Do not redefine acronyms.

The conclusion contains compelling qualitative and quantitative performance metrics.

Comments on the Quality of English Language

Good quality with minor grammatical revisions required.

Author Response

'Responses to Reviwer 3.docx' is uploaded.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The paper is good to publish, thank you.