[WIP][1.8.1, 1.9.1, 1.10.1, 1.11.0–2, 1.12.2–5] Principia—version ‎‎Kronecker, released 2024-11-01—n-Body and Extended Body Gravitation

[王小谦同学]

2 hours ago, Agustin said:

you'll probably need to upload the LOG file through an external link if you want the developers to help you. Search where it is located on your system in the How to get suppot thread you can google.

 

Sorry, I am in China, so I can't use google drive, I hope you can use this link and download it @pleroy @eggrobin

https://pan.baidu.com/s/1xL2wAyckeDCafz3nxr1XgA

[pleroy]

@王小谦同学: I was able to download your KSP.log file, but unfortunately this is not the log file that we need for debugging.  Please see the FAQs for information on reporting bugs, and where to find our log files.  Also, if you have a save that you could upload that might be helpful.

[王小谦同学]

17 hours ago, pleroy said:

@王小谦同学: I was able to download your KSP.log file, but unfortunately this is not the log file that we need for debugging.  Please see the FAQs for information on reporting bugs, and where to find our log files.  Also, if you have a save that you could upload that might be helpful.

I reported in GitHub, with the file, the game did not seriously crash, but somehow freeze, and not respond.

https://github.com/mockingbirdnest/Principia/issues/1864

[Agustin]

Hello I just want to pass by and say thank you so much. It is so beautiful and fun watching all the trajectory paths drawn from different perspectives, and helpful too because it is more precise than the stock phyics, and so much more interactive in the sense that it has more gameplay mechanics playing with different types of orbits. It's great and I love it (now playing on RSS) So yeah. Just wanted to say that.

[eggrobin]

For the new moon (lunation number 229), the new release (Δημόκριτος) is out.

Vessels are now managed by Principia when they are in the atmosphere, which means that atmospheric flights have Principia histories and predictions in map view.

The “Trappist-1 for Principia” mini-mod has been improved to better reflect the physical properties of the celestials.

See the change log for more details.

We support two versions of KSP: downloads are available for 1.4.4 and 1.3.1. Make sure you download the right one (if you don't, the game will crash on load).

[Agustin]

nevermind

Edited July 13, 2018 by Agustin

[scimas]

@eggrobin The change log says "this version supports 1.3.1 and 1.4.x," does that mean I can use it with 1.4.3 too, or only 1.4.4? Also, the topic title is still showing "[1.3.1, 1.4.3]."

[pleroy]

25 minutes ago, scimas said:

@eggrobin The change log says "this version supports 1.3.1 and 1.4.x," does that mean I can use it with 1.4.3 too, or only 1.4.4? Also, the topic title is still showing "[1.3.1, 1.4.3]."

I tested it with 1.4.3.  It works fine.  Not tested with older releases 1.4.x but should be ok.

Edited July 13, 2018 by pleroy

[drtedastro]

thanks for all of the great work and support.

cheers.

[ThreePounds]

This is my first time looking at the mod and I am absolutely blown away by it. It's surprisingly intuitive, which I didn't expect given what the mod sets out to accomplish, as I was able to get a lunar transfer and injection without consulting any tutorials. Buttons are were you expect them and clearly state what they're for. Just for giggles I loaded up a copy of my career save to see what my space craft are up to and all of them are where I'd expect them to be.

Playing with this mod is some sort of eye opener. It's such a huge step up from the simplistic stock physics and I feel like a child exploring n-body physics.

I seriously wish I had discovered this mod earlier. I'll be spending many hours in it in the future I'm sure.

[Delay]

5 hours ago, pleroy said:

I tested it with 1.4.3.  It works fine.  Not tested with older releases 1.4.x but should be ok.

Is this the first ever version of Principia able to run on an un-supported release of KSP then?

Edited July 13, 2018 by Delay

[pleroy]

8 minutes ago, Delay said:

Is this the first ever version of Principia able to run on an un-supported release of KSP then?

Probably not: we have been supporting 1.2.2 until mid-May 2018.

[DocRockwell]

I've been looking forward to this release, thank you for making such an awesome mod.

Is the bug that caused crashes when you had several gravity assists on one flight path fixed? My campaign's been stalled at 1977 with several probes launched onto a grand tour.

Can RSS Expansion (https://github.com/PhineasFreak/RSSExpansion) be added to an ongoing save game?

[pleroy]

10 hours ago, DocRockwell said:

Is the bug that caused crashes when you had several gravity assists on one flight path fixed? My campaign's been stalled at 1977 with several probes launched onto a grand tour.

Dunno, did you report it on GitHub?  We fixed two bugs that could match that description (see the change log) but it's hard to know for sure.

10 hours ago, DocRockwell said:

Can RSS Expansion (https://github.com/PhineasFreak/RSSExpansion) be added to an ongoing save game?

Nope, the solar system is constructed when you start a new game.

[Dolin]

A question: does principia integrate the complete n.body motion of EVERY massive body in game (celestials and vessels) or do you somehow differentiate between the integration of planets and vessels?

In other words, does principia, at any point, neglect the influence of ships on planets and therefore shave off some computations?

Thanks for the insight.

[Johould]

On 7/17/2018 at 3:45 AM, Dolin said:

A question: does principia integrate the complete n.body motion of EVERY massive body in game (celestials and vessels) or do you somehow differentiate between the integration of planets and vessels?

In other words, does principia, at any point, neglect the influence of ships on planets and therefore shave off some computations?

Thanks for the insight.

Are you thinking of making a gravity tractor?

[Dolin]

14 hours ago, Johould said:

Are you thinking of making a gravity tractor?

Quite the contrary: I'm concerned about in-game performance.

I'm using RSS with a ton of mods and I see a noticeable difference in performance with and without Principia.

In the case that everything (planets and vessels) is thrown into the integration scheme, I thought that maybe the motion of celestials could be completely solved before the game even loads for say a thousand years, with an arbitrary timestep, and the results stored on file.

Then the plugin would update the celestials' positions by reading them off a file, and the live integration would be reserved only for vessels. Trajectory predictions would only need to be updated live for vessels as the motion of planets is already assumed known.

 

I think this would be advantageous since in most cases all planets and moons make up half or more of all the gravitational bodies in game, which entails quite a few computations thrown away.

I think I've heard that asteroids are in fact treated as vessels in KSP, so it should still be possible to build a gravity tractor. But we could take this a step further and neglect the influence of vessels on other vessels,  no gravity tractor in this case but even more compitations skipped.

 

If, otoh, Principia already does something like this then there's not much room for improvement, hence my enquiry

[Johould]

2 hours ago, Dolin said:

In the case that everything (planets and vessels) is thrown into the integration scheme, I thought that maybe the motion of celestials could be completely solved before the game even loads for say a thousand years, with an arbitrary timestep, and the results stored on file.

That's the ephemeris occasionally mentioned in the changelog. I don't know the exact time range or storage, but the motion of celestials is precomputed.

[scimas]

7 hours ago, Johould said:

That's the ephemeris occasionally mentioned in the changelog. I don't know the exact time range or storage, but the motion of celestials is precomputed.

No, that's not what ephemeris is. Ephemeris, in the context of principia, is how the integrates the motion of celestials. The integrator to use and the time step size of the integrator.

9 hours ago, Dolin said:

In the case that everything (planets and vessels) is thrown into the integration scheme, I thought that maybe the motion of celestials could be completely solved before the game even loads for say a thousand years, with an arbitrary timestep, and the results stored on file. 

But then you have the problem of not being able to extend to arbitrary solar systems. In its current state principia can adapt to any planet pack as long as it provides proper configuration files. Which means you can start playing RSS with the state of solar system at any time in the past or future as long as you provide the proper initial state.

If you were to solve the system in advance for thousand years, you would need to store about 52 million instances of the system, an instance being position, velocity and angular orientation of each body. That is about 5 billion floating point numbers. And if I did the (rough) calculation correctly, that would be about 35 GB of raw data. Of course you could come up with clever tricks to compress it, but how much? And even then, I have no clue about the comparison between time taken for doing the calculation live vs looking up the values from a table for every update.

9 hours ago, Dolin said:

I think this would be advantageous since in most cases all planets and moons make up half or more of all the gravitational bodies in game, which entails quite a few computations thrown away.

Actually the number of vessels can grow quite big in a career game, and very quickly too. You have all those satellite contracts, your communication satellite networks, planetary bases, space stations and what not..

On 7/17/2018 at 2:15 PM, Dolin said:

In other words, does principia, at any point, neglect the influence of ships on planets and therefore shave off some computations?

I'm not completely sure about this, but I think I remember it mentioned sometime that celestials do ignore vessel influence. Although I can't think why that would be; you are anyway computing the force on a vessel due to a celestial, the force on the celestial is just the negative of the one on the vessel..

[Johould]

8 minutes ago, scimas said:

No, that's not what ephemeris is. Ephemeris, in the context of principia, is how the integrates the motion of celestials. The integrator to use and the time step size of the integrator.

Huh, where do interpolation schemes come in? Is that just interpolation within a single time step? Sets of coefficients for polynomial interpretation is how NASA releases projected positions in the real solar system, I thought they were a bit more related.

[Teilnehmer]

4 hours ago, scimas said:

Although I can't think why that would be; you are anyway computing the force on a vessel due to a celestial, the force on the celestial is just the negative of the one on the vessel..

I recon the acceleration would be far beyond the floating point precision, i.e. exactly zero.

[GrubbyZebra]

So figured I give this a shot just because, and about 35 days in I get the following message:
 

Error extending trajectory for Laythe. Error trying to fit a smooth polynomial to the trajectory. The approximation error jumped from +2.30344324226492217e-03 m to +8.35706270893752298e+03 m at time +1.57920000000000000e+06 s. The last position is [+2.82771976953634682e+10 m, +5.89455954369199753e+10 m, +3.17994282982390106e+08 m] and the last velocity is [-3.61414693067490953e+03 m s^-1, -1.47464668046310658e+03 m s^-1, +9.66125813160947615e+01 m s^-1]. An apocalypse occurred and two celestials probably collided because your solar system is unstable.

(Basically, Vall got thrown out into a Kerbol orbit). I guess the Joolian system is still unstable? Not a big deal, really just want to how to hide the message box so it isn't taking up so much of my screen.

 

Edited July 28, 2018 by GrubbyZebra

[Delay]

36 minutes ago, GrubbyZebra said:

I guess the Joolian system is still unstable?

What'S the ingame year at? You must have played for quite a long time then.

@pleroy Would it be possible to - at some point in the future - rework the way history length works? The problem I have with the way it is right now is that I usually play with the history length quite high up (e+6 area), which works well for missions to the Mun and beyond, but if a vessel is in L(K)O for a while the history leads to a lot of lag and I have to turn it down.

[GrubbyZebra]

48 minutes ago, Delay said:

What'S the ingame year at? You must have played for quite a long time then.

@pleroy Would it be possible to - at some point in the future - rework the way history length works? The problem I have with the way it is right now is that I usually play with the history length quite high up (e+6 area), which works well for missions to the Mun and beyond, but if a vessel is in L(K)O for a while the history leads to a lot of lag and I have to turn it down.

Literally less than 40 days in to a brand new game. Have OPM installed though, so maybe that has something to do with it?

[scimas]

23 hours ago, Johould said:

Huh, where do interpolation schemes come in? Is that just interpolation within a single time step? Sets of coefficients for polynomial interpretation is how NASA releases projected positions in the real solar system, I thought they were a bit more related.

I have no idea.

19 hours ago, Teilnehmer said:

I recon the acceleration would be far beyond the floating point precision, i.e. exactly zero.

That makes sense.

39 minutes ago, GrubbyZebra said:

Literally less than 40 days in to a brand new game. Have OPM installed though, so maybe that has something to do with it?

Yes, principia modifies the stock system so that the Jool system is stable. But if you make any changes to stock, it will treat it as a new planetary system and won't make stability changes to Jool system, you will have to do those on your own.