Arrowstar
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3/24 Discord AMA - Nate Simpson - SUBMIT QUESTIONS HERE
Arrowstar replied to Dakota's topic in KSP2 Discussion
Hey Nate! There's a small but hardworking subset of the KSP modding community that develops external tools to help users perform spacecraft and launch vehicle mission design. While I might have one of the longest running mods out there in this regard (KSPTOT), I'm definitely not the only one. One of the big issues I've run into with developing with KSP 1 in mind that the developers never provided any insight into how they model forces and torques on the vehicles. Given this, what are your thoughts on: Providing a KSP 2 "theory manual" that contains information regarding the math models you all have developed and implemented in KSP 2? Especially important here are force model definitions and atmospheric model definitions. Providing API documentation that includes units, relevant reference frame definitions, and data type/dimensions where appropriate? Let me give you an example as to why I would love to see this in KSP 2. Right now I'm trying to reverse engineer how KSP 1 computes lift forces on a rocket so that I can write a plugin to generate lift coefficient databases for a given vehicle. This is extremely painful in KSP 1, because A) there's no documentation and B) there's no definitions for anything. I'm basically having to rely on what other modders have figured out before me, but some of it is out of date, etc. Providing the KSP community with those two bulleted items would go a long way to helping us out! Thanks for all the fun so far, looking forward to what KSP 2 has to bring in the future! -
Yes, I was able to reproduce the issues on my end. It was an issue with the new way that MATLAB implemented their tcp/ip connection interface. Reverting to the old way resolved the issue.
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I ended up reverting some files back to a late 2022 state and I think that's resolved it. Give it one more go for me.
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Alright, go ahead and redownload the PR4 package once more. I think I've got it figured out. I honestly have no idea why this broke all of a sudden though. Something changed here though at some point. Hopefully these changes fix the issue.
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Go ahead and redownload the PR4 file. I think I've got it fixed, can you let me know if it works?
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Thanks for the note. That looks like just a warning, so you should still be able to upload a maneuver properly. Does it not work for you? Regardless, I've got it fixed and I'll upload a new verison of PR4 here soon.
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Title says it all. I've got a very low Munar orbit that has a periapsis below the terrain, but it's not being detected as a crash yet. See email. By the way, the issue with the orbit periapsis and apoapsis changing is still not fixed. Periapsis goes down, apoapsis goes up. Looks like an integrator issue to me, but I can't be sure.
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Hi everyone, Given a particular Vessel, is it possible to set its yaw, pitch, and roll? Either directly or indirectly via quaterion is fine with me. Thank you!
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Hi everyone! Tonight I've built KSPTOT v1.6.10 pre-release 4. Here's the change log: LVD: Implemented ability to only plot certain events in the View Profiles. LVD: Events are now numbered in the listbox string with equal number of digits for each event. Also frozen events now get a snowflake symbol instead of **. LVD: Added DERIVEst method for computing gradients and Jacobians. LVD: Fixed bug with getPositOfBodyWRTSun() LVD: Update NOMAD 4 mex that allows for parallel processing while optimizing. Lots and lots of bug fixes, mostly within LVD. @Gilph, there should be a fix in there for the bug you described. Let me know if it worked or not. As always, if you find any bugs, please let me know! Happy orbiting.
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Take a look at the Workaround section of this page. Some of the comments may also have fixes you can try. Substitute any reference to the MATLAB install directory with the MCR directory. https://www.mathworks.com/matlabcentral/answers/397138-why-do-i-get-a-matlabwindow-application-failed-to-launch-error-when-launching-live-editor-app-des
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Okay, how about this. Can you give me orbital elements for the vehicle immediately before and after the Kerbin departure burn when you execute it in KSP?
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Can you send me a picture of what the trajectory looks like when you use the burns in KSP as provided by LVD? And can you send another picture with a close up of the Kerbin departure burn? Here's why. I suspect that your departure burn isn't being modeled correctly and you're not in the right place. That is, the true anomaly of the burn is probably not where you think it is in KSP. There's basically no way for LVD to be as off as you're showing it is without there being a modeling error somewhere. If you track that down, you should have the answer to the issue.
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Thanks! And which part of the scenario is the problem? Where are you not getting close enough?
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Could you provide me with the LVD MAT case file you are working with? It can be hard for me to understand what you're struggling with without being able to see it. Thanks!
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OP, do Kerboscript scripts generally work with your mod?
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Alright, here's what you need to do to start, I think: Restart KSPTOT entirely. Make the bodies.ini file for your configuration. Open up KSP, go to a spacecraft or any rocket on the pad. Then in the main KSPTOT GUI window (with the porkchop plot), File -> Create Bodies File from KSP. Update the file you just created to use numerical propagation for the celestial bodies, as I think this is what Principia is doing under the hood. Add the following to each body's entry: propType = numerical_integration Just as a warning, this can be pretty slow, so if you can get away without the numerical propagation of the celestial bodies, I would skip this step. Load this file. File -> Load Bodies From File. Re-open LVD. Turn on Third Body Gravity. Scenario -> Edit Initial State. Push the Edit 3rd Body Gravity Properties button. Select the bodies you want to use. Turn on the 3rd body gravity model. Open up your first event. Select the Force Model Propagator. Hit the Propagator Options button. Select 3rd Body Gravity and save/close the dialog. Repeat this last step for each event in your mission. Let me know if this helps!
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Thanks for the info. In LVD, do you have third body gravity forces turned on? And are you using the Principia bodies.ini file that I include with KSPTOT?
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It sounds like what you're doing is a bit more complicated that RMS was designed for. You'll probably need to use the more general purpose LVD. All RMS does is give you a transfer orbit and DV vectors to hit your desired target exactly. You can't specify a target orbit because it was really designed to be used for rendezvous with spacecraft. RMS definitely doesn't work with Prinicipia. If you want to go N-body, you'll need to use LVD. It's the only tool in KSPTOT that can handle that, but I'll tell you up front that the learning curve for n-body gravity is a bit steep. Feel free to ask questions!
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Yes, the central body for a transfer from Earth to the Moon wouldn't be the Sun. The main porkchop plotter tool isn't actually what you want to use here. For a simple rendevous analysis, use the Rendezvous Maneuver Sequencer tool (Tools -> Maneuver Planning). For a more detailed analysis, you can use Launch Vehicle Designer, which despite the name handles generalized spacecraft and rocket mission design and analysis. Start with RMS first and you can graduate to the more difficult LVD later. Let me know if you have any other questions!
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This is almost certainly a case of the sphere of influence radius assumption in MFMS (it being infinitesimal). It could also be that the burn isn't in the right spot in KSP, and since your eccentricity is very small, mean anomaly/true anomaly can get squirrelly. Try the maneuver in LVD, which is using a physics engine similar to KSP, to see if you can figure out what actually happened. Unfortunately, without the contents of your ksptot.log file, I can't really say. I would urge you to use Launch Vehicle Designer over MA, though. LVD is more stable and I've done a much better job with it. Despite the name, LVD does the same thing MA does, just much better.
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Hey Dakota, thanks for the info! Could you comment on my thought about providing documentation and a theory manual for those of us who work on projects that involve modeling KSP dynamics outside of KSP?
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My biggest concern is documentation actually. My software only needs minimal access to KSP 2's data, but what I really need is a theory manual that describes the force and torque models on your vehicle. That includes drag models, atmosphere models, lift models, engine thrust models, etc. It's my biggest hope that the devs will provide this information to us modders so we don't have to reverse engineer it ourselves.
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Glad to see this project is still alive!
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Feel free to add me as a signatory to the letter. I develop the KSP Trajectory Optimization Tool (KSPTOT), which includes a KSP plugin mod.
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