I'm interested in approximating the force generated by the grid fins on a Falcon 9 rocket during its descent phase. However, I currently lack specific data and equations for this calculation. Can anyone provide insights, guidance, or resources on how to estimate the force exerted by the grid fins on a Falcon 9 rocket?

I'm looking for simpler methods or approximations that can provide a reasonably accurate estimate of the grid fin forces given the current velocity, air density and angle of attack of the grid fins.

For example, would it make sense to try to recreate something as shown in slide 19 in this presentation? I tried to find the paper associated with it, but it seems that the author never published it.

As mentioned in this thesis, the behavior changes a lot depending on if you are in sub- trans- or supersonic flight. However, this might already be too complicated for my use case.

  • $\begingroup$ The things are composed of flat plates. There should be a healthy amount of information on lift characteristics of flat plates across a wide regime of flow conditions out there. I would suggest estimating the forces by computing for one cell line of the grid fines then multiplying by the number of cell lines. $\endgroup$
    – A McKelvy
    Sep 12, 2023 at 0:26
  • $\begingroup$ Do papers like arc.aiaa.org/doi/epdf/10.2514/3.55704 give you the data you need? $\endgroup$
    – Hobbes
    Sep 12, 2023 at 8:28
  • $\begingroup$ If you don't have any data to compare the results of your calculations to, how will you ever know if what you are doing is correct? $\endgroup$ Sep 12, 2023 at 19:19
  • $\begingroup$ You could run a cheap CFD sim on a grid-fin model, and that would also kickstart you being able to do so yourself! And welcome to Space Exploration! $\endgroup$ Sep 14, 2023 at 4:31


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