Leading-Edge Vortex Lift (LEVL) Sample Probe for Venusian Atmosphere

Round 1

Reviewer 1 Report

The paper Leading Edge Vortices Lift (LEVL) Sample Probe for Venusian 2 Atmosphere presents a small and lightweight sampling system whose design is inspired by the sycamore seeds and leaves. The paper is well written and provides all necessary details in a minimalist style. I would personally appreciate a paragraph or so in the introduction on the science measurements but the current approach with referencing [1,2,3] is OK.

The paper presents the theory, the tradeoffs, as well as the experiments and results. The paper presents somewhat intermediate results which is acceptable for the VLF special issue. The authors identify that the falling speeds are 1.5-2.5 greater than expected which requires further work, especially with TA2. I think this  is a publishable result with the paper providing details on the experiment design. 

The paper's language is perfect and I learnt a new phrase myself. The illustrations and the video are a great value clearly explaining the experimental work. Some graphs are difficult to read in grayscale.

Thanks! 

Author Response

I am submitting the revised version of the article entitled “Leading Edge Vortices Lift (LEVL) Sample Probe for Venusian Atmosphere” to the Aerospace Special Issue "The Search for Signs of Life on Venus: Science Objectives and Mission Designs" on behalf of the authors: Christopher Isaac and Nicholas Jones. See attached file for the point by point response to the reviewer's comments. 

Author Response File: Author Response.docx

Reviewer 2 Report

General Comment

This manuscript reports a very interesting technical study as the composition of Venus atmosphere is very challenging for the scientific domain. This paper is presenting an additional way how to better study and analyze it.

Considering that such a mission is a forthcoming topic for space research and it may become reality in a few years, this paper is recommended for publication, provided that the authors revise the manuscript according to the following comments and suggestions which could improve the quality and understanding of the paper.

There are several paragraphs in which the pronouns “our, we” is extensively used. The use of first person in scientific papers is acceptable only in abstracts, discussions and conclusion sections, although not indicated.

The pronouns could be substituted as follows:

Line 21: “we have identified…” to: “an unmet need for a small, lightweight sampling system was identified to run […]”. The authors are encouraged to reconsider the use of pronouns in the manuscript.

Abstract

Please correct the following: Line 13: “…able to carry a total mass of 920 grams…”

Define the “MEMS” abbreviation at Line 10.

Introduction

The introduction section should be improved and more references should be added. This section should take into consideration the most relevant studies on the subject to build a complete scientific framework.

At this moment at least two of the actual references are very comprehensive in terms of information, but the authors should not limit to these as single points bibliography resource. There are several studies and missions’ architectures which are proposing cost-effective balloon missions. I propose to the authors to deeply present these aspects in the introduction, such way to assure a smooth transition to the paper main topic. Any information with respect to the architecture of the Venusian mission (scientific objectives, spacecraft structure etc.) is encouraged and must be done.

Taking into account the actual information presented into the paper, it is not clear how the maximum mass of 920 grams was defined. Also, the overall volume shall be defined and considered for the mission architecture, along with some information about the foreseen materials and payloads. The payload mass and dimensions are presented only in the conclusion. 

Consider presenting some details about the materials and payload admissible mass and dimensions within the main text.

Also, Subsection 2.2 shall be moved to Section 3, as it does not have a Theory – lift equation information. The information about materials and payload can be addressed before Table 1, as a part of design requirements.

For example, in ref [1] there are included four mini probes which will be deployed from the balloon. These probes will be featured with “parachutes, a parawing, risers and a chute/drag streamer”. I suggest to the authors to include a light trade-off to better highlight the LEVL advantages and strengthen the choice of their concept.

The reviewer suggests to include additional references into the introduction, for example at the paragraphs 4 and 5 (between line 31 up to 36).

Also, the abstract and the conclusions can be extended and improved.

Please correct the following: Line 31: “Inspired by nature, an investigation has been made/conducted…”.

Please correct the following: Line 44: “We used data on the Venusian atmosphere…”. Avoid using the pronouns in the main text, suggestion: “The data on the Venusian atmosphere and its density was used to predict […]”

Section 2.

Equation 1. fluid density does not appear in the equation. Please verify the correctitude of the equation.

Please correct the following: Subsection 2, Line 59: “…hence equation (1) can be rearranged to give:”

Subsection 2.2:

-          please define the “wing” and “nut” terms either in the main text or on a representative figure.

-          The font used in table 1 is not the same as in the paper. Please make sure the correct template is used and followed properly.

Line 102: “examination of this data could provide support to the hypothesis that […]…

Subsection 2.3 (Line 121) – It would be interesting to present more information about the materials and the selection process. For example, in Subsections 3.2 and 3.3 the PLA material is specified. How this material was chosen?

Also, I recommend for the figures included in the manuscript to be rearranged and to follow the text where they are referenced. The exposition of the test articles description, the test set-up and the experimental results are not clear and the paper should be better organized and structured. Following the text as it is right now, figures and discussions of the results proved to be quite difficult. The reviewer is suggesting to improve this aspect.

Section 3

- what does controlled environment mean? Please define the conditions of the controlled environment.

- It would be nice to present the specifications of the flatbed scanner;

- the drop test set-up shall be presented in more details.

Regarding the test articles geometries, in ref [4] there is presented the way how those geometries were defined. Maybe it will be helpful to follow the same approach and to explain in more details which strategy/rationale has been applied for the geometry definition. Also, a CFD analysis, first on Earth environment and then in Venus environment may be useful for the following steps of your project.

Specify why TA1 was dropped from a height of 62 meters. This height was selected taking into account the Venus environment/atmosphere specifications? The same question for TA2. Why TA1 and TA2 were not tested under the same conditions (e.g. same drop height)? Please discuss this in the main text.

Same comment in this section as above in respect to the figures placing. Consider bringing them where they are referenced to have a correct flow of information and better understanting.

Line 172. What do the authors mean by “and above” in “see [8] and above”?

 Section 4

Table 2 – could you specify what means Letter and ID? How were the two assigned to the sycamore seeds? Also, the same observation as in Table 1 is applicable here (different font compared to paper text). Make sure the correct paper template is used (font and size).

Subsection 4.3.1 – The caption with the figures has an error. Insert figures after close to where they are first mentioned.

The figures format should be adjusted and, furthermore, the size of the figures of the designs should be increased and the text of the figures should be of the appropriate size to be readable. For example:

-          Figure 1, Figure 3 – the font is quite small;

-          Figure 3 – is the figure plotted by the authors or is taken from another source? Please provide a reference if necessary;

-          Figure 2 – zoom-in for the wing-cut sample 4&5;

-          Figure 5 – increase the blue dot dimension and also the font;

-          Figure 8 – please describe the materials and the main components;

-          Figure 9 – it would be nice to highlight some overall dimensions and the IMU location

-          Figure 13 – include the axis names, increase the overall size, it is quite difficult to read the numbers as it is;

-          Figure 15 and Figure 20 – the picture quality is quite poor. I understand that the altitude was high. If it is possible, please substitute these pictures with ones of better quality

 Subsection 4.5

Define acronyms VT, VB and ESL in the main text, not the table.

Section 6

Line 354: “…before the probe gets crushed near the surface of the planet.”

The observation about follow-up research using also a CFD analysis is a strong point and encouraged, as this provides relevant data to additional research in the space domain regarding Venusian atmosphere/probe sampling.

From my point of view, in order to reduce the risks and to increase the maturity of the proposed solution, a comparison between CFD results and tests is mandatory. Based on this, you will be able to optimize the design taking into account the Venus atmosphere characteristics, followed by dissemination of the findings in future quality papers.

Please perform a literature survey regarding the 3D printing technologies. From my opinion a 0.8 wall thickness will be very challenging to be manufactured.

First paragraph of the Conclusion Section could be moved to the Discussion Sections.

For the above-mentioned reasons, the reviewer proposes to publish the manuscript after major revisions.

Author Response

I am submitting the revised version of the article entitled “Leading Edge Vortices Lift (LEVL) Sample Probe for Venusian Atmosphere” to the Aerospace Special Issue "The Search for Signs of Life on Venus: Science Objectives and Mission Designs" on behalf of the authors: Christopher Isaac and Nicholas Jones. See attached file for the point by point response to the reviewer's comments. 

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The paper can be published now.