Development of the thruster model (ThrModel)

[AlexKulov]

Hello!
First of all, I would like to thank the community that develops this project and personally Eric T. Stoneking
42 is amazing project, which I use in my research and education activities many times.

I'd like to contribute to this repository and have a few ideas.
But I couldn't find any instructions (like CONTRIBUTIN.md).
For example, I'd like to clarify the thruster model.

1. introduce build-up time и tail-off thruster time (build-up и tail-off time significantly affects the dynamics of angular control, since the thrusters can operate for fractions of a second and not reach the nominal mode). See the picture from the book "Design of thruster control systems for spacecraft"
   https://raketoff.wrk.ru/raketoff/Proektirovanie_reaktivnyh_sistem.pdf

2. Minimum interval between starts
3. Calculate the number of starts and fuel consumption
4. Introduce restrictions for proportional mode: minimum and maximum levels
   (For example, I don't know of any liquid thrusters that can operate in proportional mode, but electric thrusters can).

Could you tell me how I can make my own changes: completely replace the ThrModel function or write my own? How can I add new parameters (such as thrust buildup time or specific impulse), create a separate file (such as Drag/Jitter Input File Name), or add new lines to the Thruster Parameters section of the SC_.txt file?

Thanks for your answer

[ericstoneking]

Hi Alex,

Thanks for the kind words. I'm glad you find 42 useful.

For various reasons (legal, practical, and to be honest personal), I only very rarely accept code contributions. I do try to address bug reports, and I do sometimes accept feature requests. Having limited time and resources, I do have to manage my priorities.

The good news is, you are absolutely welcome (encouraged even) to customize your clone of 42 to suit your problem and your preferences. For your thruster response example, take a look at the filter functions in Kit/Source/sigkit.c. Modify ThrModel to taste. See examples in 42init.c (InitSpacecraft, for instance) of how I read input files. Look in 42report.c for examples of how I write data to output files. See Include/42types.h to add properties to the thruster structure (struct ThrType). The rest I leave to your imagination.

Regards,
-Eric

[AlexKulov]

Sorry for my long range answer (whatever that means).

1. I think Project 42 is more than just a simulator. It's a good library of models and algorithms for anyone interested/work in spacecraft(s) control. And I think it would be great if this library expanded.
2. I looked at a lot of 42 forks and didn't find any well-documented changes that differentiate from "parent" 42. Of course, there are commits, but that's worse than if someone simply wrote down in ReadMe (the exception, probably, is
   https://github.com/pavelgalchenko/deepthought).
3. I already have my repo, the core of which is 42 (like git submodule).
   https://github.com/AlexKulov/42shell
   In it, I'm trying to:
   3.1 Make it easy by Qt for students to get started (independent from Win/Linux)
   3.2 Specifically introduce changes/additions to 42's workflow (models/algorithms) without affecting the core 42 code.
   But sometimes I find that my changes look much simpler (more elegant, more organic) in 42 itself.
4. Perhaps I should create my 42 fork, in which I'll incorporate changes from 3.2 (and document them in ReadMe, as I mentioned in 2.)

In short, I hope to make the fork useful and accessible to a wide range of people, and to briefly describe the changes/additions made (to enrich the many features of 42).
For example, a new thruster model (as I described earlier), a primitive power supply system model, and simple solar orientation, nadir orientation, and point orientation functions (based on latitude-longitude coordinates) were added to the 42shell repository.

Eric, if you have a moment, I'd appreciate a brief comment on any of the points above. I'm especially interested in your opinion on the fork vs. add-on approach (see 3.2), and whether there have been similar initiatives in 42 community.

P.S.: My colleague found this article and said it describes the ThrusterPlumeFrcTrq(...) function. Maybe this will be useful to someone.

Woronowicz_M_S_,_Didier_F_G_R_On_plume_flowfield_analysis_and_simulation.pdf

[ericstoneking]

Fork. There may be similar initiatives out there. It's up to you and them to find each other.