Issues #18, #72, #73, #74, #69: team-07

[Jasn6z]

Pull request type

Please check the type of change your PR introduces:

• Code base additions (bugfix, features)
• Code maintenance (refactoring, formatting, renaming, tests)
• ReadMe, Docs and GitHub maintenance
• Other (please describe):

Pull request checklist

Please check if your PR fulfills the following requirements, depending on the type of PR:

• ReadMe, Docs and GitHub maintenance:

  • Spelling has been verified
  • Code docs are working correctly

• Code base maintenance (refactoring, formatting, renaming):

  • Docs have been reviewed and added / updated if needed
  • Lint (black rocketpy) has passed locally and any fixes were made
  • All tests (pytest --runslow) have passed locally

• Code base additions (for bug fixes / features):

  • Tests for the changes have been added
  • Docs have been reviewed and added / updated if needed
  • Lint (black rocketpy) has passed locally and any fixes were made
  • All tests (pytest --runslow) have passed locally

What is the current behavior?

Enter text here...

What is the new behavior?

Enter text here...

Does this introduce a breaking change?

• Yes
• No

Other information

Enter text here...

[FranzYuri]

Hi @Jasn6z! Great work here! This new class Analysis is incredibly organized and have some very interesting methods.
A few questions though:
First, at snatchforce_calculator, what is the formula you used, and are you sure using the velocity of impact was the way to go? Also, were you indeed intending to have as output a Function object? Was the idea to have a function of altitude vs snatch force?
Secondly, I could not find where you got the formula for chute_radius_finder at line 101 in Analysis.py. Are you sure this formula could be used for toroidal parachutes?

[Jasn6z]

Howdy! To answer your first question, the formula I used for the snatch force was based on two different things. We compared formulas used by the Naval Surface Weapons Center to calculate parachute shock force on payloads in this <https://apps.dtic.mil/sti/citations/ADA180901> report with formulas put forth by the AIAA association *here <https://arc.aiaa.org/doi/abs/10.2514/3.58321?journalCode=ja>*. These equations produce snatch force as a function of final velocity, so I decided to utilize the ground impact velocity. I feel that this is a reasonable assumption to streamline the function, as one would tailor their parachute to a specific landing velocity. With more time, a more refined formula could be made to take more into account and produce a more specific result. As for the outputs of the functions you mentioned, they are indeed supposed to be function outputs. My teammate brought up the idea that someone using RocketPy would find it more useful to be able to see a range of possibilities rather than just one. Our thinking was that a function would be more versatile in allowing an inexperienced user to easily get a range of answers granting them insight on ways to optimize their rocket without any tedium or frustration. In regards to these function outputs, unfortunately, we did encounter an issue we were unable to resolve in the given time. The output of the launch rail exit velocity by mass function was only returning one repeated value as opposed to the many different values we expected. I suspect that this is simply a problem with the internal calculations done by RocketPy’s flight simulation class or at least our understanding of them. I hope this answers your question, and feel free to ask me for any more clarification you need. Thank you for your support -Jae-son Rivera (512)-468-4886 ***@***.*** ***@***.***

…

On Thu, Sep 1, 2022 at 7:17 PM FranzYuri ***@***.***> wrote: Hi @Jasn6z <https://github.com/Jasn6z>! Great work here! This new class Analysis is incredibly organized and have some very interesting methods. A few questions though: First, at snatchforce_calculator, what is the formula you used, and are you sure using the velocity of impact was the way to go? Also, were you indeed intending to have as output a Function object? Was the idea to have a function of altitude vs snatch force? — Reply to this email directly, view it on GitHub <#110 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/A2W33WGSM23GZ44W2RW53JTV4FBSFANCNFSM5734SA3Q> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[FranzYuri]

Hi @Jasn6z ! Again, great work here! I am giving you 50 points for the issues 18 and 69 (both of medium difficulty) and also 50 for the issue 73. Now, about the issues 72 and 74: at 72 the formula you used to find the diameter through the area is wrong, as it should be D²*pi/4=Area. Indeed, searching closely I found it was also wrong at Fruity Chutes, but I still will have to give you a penalty, resulting in 40 points instead of 50.
At 74, I read the sources you gave me and, looking at the calculations presented at https://apps.dtic.mil/sti/citations/ADA180901, you forgot the shock factor (x1), that should be multiplied by the drag force of the parachute fully open in its final velocity (you can read further at pages 10 and 11).

As shown here, we cannot ignore this coefficient or consider it to be 1, as it affects greatly the final result. Therefore, I unfortunately will not give you points for this task.
With all that, you got 140 points for this pull request! A gigantic congratulations for you and your team!

If you have doubts or disagree with my assesment fell free to contact us in any way you like (here, on discord, linkedin or so on).

[Gui-FernandesBR]

Regarding issues 18 and 69, May recieve an extra 20% points since it was the onlly team solving this challege

[FranzYuri]

HI again! Unfortunately, after closer examination we concluded that it would not be fair to give your team points for the issue 72, as it was not a complete solution for the challenge. For designing a parachute, it was expect the code to find at least the height and radius for an ellipsoidal parachute, internal and external radii for a toroidal, allow user to choose the area of the vent and so on. The current implementation presented on the method chute_radius_finder does not help on any of that and also fails to find the right D0 of the parachute, as I said earlier.