Rotating Detonation Combustion for Advanced Liquid Propellant Space Engines

Round 1

Reviewer 1 Report

The paper by Heister et al. deal. with an interesting topic and it can be of interest for the community. However to be published in Aerospace some revisions are needed: 

- The title should address the fact that is a simplified and lumped parameters analysis 

- The abstract needs to be improved, it seems more a short introduction than an actual abstract

-The introduction should be improved, it features just 3 citations which is not common for a scientific article 

- The quality and resolution of some figures (like Fig.2 ) should be improved 

- When discussing eq 2 and 3 which are the "various published results"? no citation is present in such part.   

-From page 14 the references link is not working, this is not acceptable. Please check it multiple times before submission 

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

This paper presents an overview of potential advantages of the use of rotating detonation rocket engine as a space propulsion mean.

page 4 "the nozzle pressure ratio is infinite" is misleading as one may think to the chamber-to-exit rather than to chamber-to-ambient pressure ratio (the fact that the latter is infinite in vacuum is obvious)

The upper bound reported in Table 1 seems far too optimistic. It is not clear to this reviewer how the jet can reach exhaust speeds greater than those given by using 100% of the energy available for instance for the formation of H2O from H2 and O2 even if we consider those propellants heated at 300 K. I expect an upper bound of 530 s considering stoichimetric proportion of H2 and O2 quite lower at OF=2.7. How can you get 554 s? Where dose this energy come from?

There are errors in citations (see pages 14 and 15) and in the reference list (double numbering, missing reference [7] in the square brackets reference number, number 26 of the list associated to a line with pages of [26]).

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Very nice written paper.  There are some formatting issues.  Towards the end of the paper figures and equations have shifted.  The are some "Error! Reference material not found" towards the end of the paper.  Ref 32 is in bold.

You mention the potential performance gains of 3-14%.  Has anyone achieved anywhere close to this performance gain.  What is the amount of fuel and oxidizer needed to detonate to achieve these gains.  The parasitic loses of deflagration seem to be limiting factor that is very different that a conventional engine.  Do you see a path to limiting deflagration?  With the increase in detonation pressures the feedback into the injectors and injector manifolds is significant.  Do you see a path to limit this feedback?  How does the feedback affect performance? In Figure 3, you show a flared cowl and IE cowl.  Do you believe this is the most efficient way to introduce the exhaust gases onto the aerospike nozzle.  Would a conical chamber matched the angle of the aerospike nozzle also work?  Would the reduced area at the exist cause issues with the detonation?  Detonation of liquid systems near the wall is a concern, does moving the reaction away from the wall decrease performance?  Are deflagration loses increased in this case.

Author Response

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Author Response File: Author Response.pdf