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[WIP][1.5.1, 1.6.1, 1.7.x] Principia—version Fourier, released 2019-10-28—n-Body and Extended Body Gravitation, axial tilt

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@AlliedForth @hypervelocity @scimas: I have added some words to the FAQ but basically reusing a save that was not created with Principia will have strange results because the celestials will be in different places.  It should not crash, but it may or may not be what you expect.

This is unrelated btw to the notion of adding new vessels: vessels get created and removed all the time as part of normal gameplay (e.g. when stages separate or when a rendezvous happens) so this is something that we have to handle properly. 

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9 hours ago, pleroy said:

d btw to the notion of adding new vessels: vessels get created and removed all the time as part of normal gameplay (e.g. when stages separate or when a rendezvous happens) so this is something that we have to handle properly. 

Hi everyone, just a small question, i understant that principia need more work of stabilisation and search of equilibrium in forces etc... when you conceive new planets through Kopernicus. But what are the mods that have done this job or now ?

I imagine that RSS is ok about that, but what about Outer planet mod, for example ? Have you tried the latest release with principia recently ? 

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On 4/22/2018 at 4:58 PM, msnbcorp said:

Hi everyone, just a small question, i understant that principia need more work of stabilisation and search of equilibrium in forces etc... when you conceive new planets through Kopernicus. But what are the mods that have done this job or now ?

I imagine that RSS is ok about that, but what about Outer planet mod, for example ? Have you tried the latest release with principia recently ? 

@msnbcorp I might be wrong, but if I am not misinterpreting the OP, it seems the below is "surprisingly stable":

 

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On 22/4/2018 at 1:28 AM, msnbcorp said:

Hi everyone, just a small question, i understant that principia need more work of stabilisation and search of equilibrium in forces etc... when you conceive new planets through Kopernicus. But what are the mods that have done this job or now ?

I imagine that RSS is ok about that, but what about Outer planet mod, for example ? Have you tried the latest release with principia recently ? 

Go on principia github and hunt down a closed issue. The issue was about supporting different gravity models / integrators for different solar systems through config files. That issue had another github profile linked. That linked guy specifically designs solar system that should be stable even under proper N body gravitation, ie stable with Principia.

I will try to find it myself once I get on a pc, but hopefully you will find it before that.

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Thanks for answering.

Other question : how goes principia with momentum conservation ? 

Does it take care of this or could it work fine with an other mod like persistentrotation ? 

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I have an install of rp-0 on 1.3.1 with both principia and persistent rotation, and things do persistently rotate through timewarp. I haven't tested angular momentum conservation vs saves/reloads reverts.

However, i think there is an issue with how principia implements axial tilt that leads to spin-stabilised craft changing orientation during SoI change, potentially causing loss of sunlight, if that's what you're after

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After few tests, it appears that persistent rotation does not really calculate rotation while unloaded (it calculate it only when needed, it seems, for performance reasons i suppose). So when unloaded if you want to take care of persistent rotation for other mods (for example the great background processing or TLS that calculate illumination and EC running/charging while unloaded) you currently can't really. (these type of mods use standard rotation for unloaded calculation as persistent rotation don't manage the unloaded rotation)

I have search for a workaround, but no luck.

I think that as principia is dedicated to real physics and made external calculation continuously, it should be a good idea to implement it directly in this mods ...

 

Future release idea may be ? 

Edited by msnbcorp

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On 4/30/2018 at 2:10 AM, nanomage said:

I have an install of rp-0 on 1.3.1 with both principia and persistent rotation, and things do persistently rotate through timewarp. I haven't tested angular momentum conservation vs saves/reloads reverts.

However, i think there is an issue with how principia implements axial tilt that leads to spin-stabilised craft changing orientation during SoI change, potentially causing loss of sunlight, if that's what you're after

That is true. Missions which rely on spin stablised probes holding orientation (for solar panel orientation like Pioneer V, or to remain aligned for capture burns like Pioneer I) are pretty much impossible with Principia.

I bug reported it on Github and it's a known issue.

https://github.com/mockingbirdnest/Principia/issues/1639

Edited by Damien212

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On 4/22/2018 at 3:58 PM, msnbcorp said:

Hi everyone, just a small question, i understant that principia need more work of stabilisation and search of equilibrium in forces etc... when you conceive new planets through Kopernicus. But what are the mods that have done this job or now ?

I imagine that RSS is ok about that, but what about Outer planet mod, for example ? Have you tried the latest release with principia recently ? 

I have created a set of patches for a few planet packs here, though I will warn you, with New Horizons, Kerbin's rotation period speeds up to 35 minutes and I haven't figured out how to fix it.

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On 4/30/2018 at 9:59 PM, msnbcorp said:

I think that as principia is dedicated to real physics and made external calculation continuously, it should be a good idea to implement it directly in this mods ...

Future release idea may be ? 

It has not escaped our notice that the specific physics computations we have implemented immediately suggest a possible extension to support angular momentum conservations.  As a matter of fact, quite a few of the classes that manage parts, vessels and pile-ups were designed with this in mind: "if, in addition to position and speed, we also had rotation and angular momentum, then it would still work because...".  We just never got to implement it.  A bit of design will be required, but I think that the foundation is sound.

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Is there a way to display Ap/pe of two (or more) bodies simultaneously, e.g. Ap/Pe of both Kerbin and the Mun?

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For the new moon (lunation number 227), the new release (Darboux) is out.

This release:

See the change log for more details.

We support two versions of KSP: downloads are available for 1.4.3 and 1.3.1. Make sure you download the right one (if you don't, the game will crash on load).

Darboux does not support KSP 1.2.2, as Realism Overhaul and Real Solar System now support 1.3.1.

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Principia most certainly intrigues me, but I was wondering if it's possible to "turn off" the mod in settings when starting a new game?

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5 hours ago, SpaceN00b said:

is there still a link to cramer 1.2.2?

Cramer for 1.2.2 is at https://goo.gl/XgRdRP.  We won't be looking into bugs or otherwise supporting Principia versions that target 1.2.2, though.

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Rephrasing my previous question: are there options in the difficulty menu when starting or editing a game to switch between principia physics and stock physics? I figured I'd ask before I ruin the progress in my older save.

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6 hours ago, mr. engino said:

Rephrasing my previous question: are there options in the difficulty menu when starting or editing a game to switch between principia physics and stock physics? I figured I'd ask before I ruin the progress in my older save.

No, as of now such an option isn't available. It is also advised to not install or remove Principia in the middle of a save. Reference

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15 minutes ago, scimas said:

No, as of now such an option isn't available. It is also advised to not install or remove Principia in the middle of a save. Reference

Ok. I guess what I could/should do then is make a copy of my KSP and install principia there; I'd have to anyways, since I have kopernicus mods installed...

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4 minutes ago, mr. engino said:

I guess what I could/should do then is make a copy of my KSP and install principia there; I'd have to anyways, since I have kopernicus mods installed...

Not sure if Kopernicus automatically means this, @pleroy might answer that better, but if you're using the stock system with slight modifications you'd have to modify the Jool system yourself. Principia changes the otherwise very unstable system to make it (at least somewhat) stable, but as soon as the system is modified Principia won't add its modifications to the system.

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1 hour ago, Delay said:

Not sure if Kopernicus automatically means this, @pleroy might answer that better, but if you're using the stock system with slight modifications you'd have to modify the Jool system yourself. Principia changes the otherwise very unstable system to make it (at least somewhat) stable, but as soon as the system is modified Principia won't add its modifications to the system.

@Delay is right: if using Kopernicus, you want to look at this section of our FAQs.

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Well, I gave it a try, from first experiences I find it quite fascinating. A question for the masses though: just out of curiosity, would something like MechJeb still work, or would it wig out from the new physics?

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18 hours ago, mr. engino said:

Well, I gave it a try, from first experiences I find it quite fascinating. A question for the masses though: just out of curiosity, would something like MechJeb still work, or would it wig out from the new physics?

it won't be as accurate as it was before with stock physics but I still find it useful though - it helps me approximate manoeuvre nodes and plot trajectories. I use the data that MechJeb offers and try and replicate it within Principia's flight planner. Simple orbital operations such as inclination changes or Ap/Pe changes work just fine with MechJeb and you can plot them as usual.

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On 5/15/2018 at 2:14 PM, mr. engino said:

Well, I gave it a try, from first experiences I find it quite fascinating. A question for the masses though: just out of curiosity, would something like MechJeb still work, or would it wig out from the new physics?

"bit wiggy"

it doesn't know anything about N-body and uses KSP's maneuver nodes which don't know anything about N-body.

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While the Principia UI looks good on a 2560 × 1440 screen like in the screenshots of the OP, on smaller screens, it eats just too much space off the screen.

I’m trying now to add an option to make the mod’s UI more compact.

Step 1 I’ve done is adding the Blizzy’s toolbar support. Using the Blizzy’s toolbar, the player can keep the main Principia window hidden most of the time, and thus, save some screen space.

68747470733a2f2f692e696d6775722e636f6d2f

The buttons are:

  • top row in the screenshot above (from left to right):
    • switch Principia GUI on/off (doubles the AppLauncher button);
    • show/hide the Settings (main) window;
    • show/hide the Plotting frame selection window;
    • show/hide the Flight plan window;
  • bottom row in the screenshot above (from left to right):
    • select target celestial;
    • select target vessel;
    • toggle patched conics;
    • toggle sun lens flare.

Any ideas of what other buttons could be added?

 

A possible Step 2 (not implemented yet) could be compactification of the Plotting frame selection window, because this

4Cqn1qb.png

is too sparse.

I believe,  it could be as tiny as in this sketch:

gbSn0MW.png

(with the mode descriptions in tooltips).

You could just keep it on the screen not bothering to hide it every now and then.

Edited by Teilnehmer

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