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[WIP][1.8.1, 1.9.1, 1.10.1, 1.11.0–2, 1.12.2] Principia—version Halley, released 2021-11-04—n-Body and Extended Body Gravitation


eggrobin
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35 minutes ago, Sesshaku said:

Cool, just wanted to confirm if it was just hard, or something was wrong with my install.

Any tips for launching from Cape Canaveral? Like at what angle should I aim an orbit and such. Or if it's possible to aim a polar orbit like the soviets from there. I am afraid I don't have much data on real historical maneuvres.

You can achieve polar orbits at any launch site you want, it's just gonna cost you more delta-v the closer you are from the equator. You can use mechjeb Prime Vector Guidance (PVG) to automate launches to a specific orbit inclination. But remember that the minimum inclination you can achieve for efficient use of fuel is always your launch site inclination.

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13 hours ago, Sesshaku said:

Cool, just wanted to confirm if it was just hard, or something was wrong with my install.

Any tips for launching from Cape Canaveral? Like at what angle should I aim an orbit and such. Or if it's possible to aim a polar orbit like the soviets from there. I am afraid I don't have much data on real historical maneuvres.

You can always reach an orbit with a higher inclination than your launch site, no matter where that launch site is located. You cannot reach an lower inclination orbit than your launch site, unless you do something like a dogleg maneuver during the launch.

The angle you aim at for any given launch depends entirely upon what kind of orbit you need to target for the mission you're flying. If you have a target inclination in mind, then you can calculate your Launch Azimuth to figure out what angle you need to be aiming toward.

All that being said, NASA does not launch polar missions from Cape Canaveral. This isn't because they can't from an orbital mechanics perspective, but rather doing so would require overflying the northeastern US or Cuba and South America. The maximum inclination typically achieved when launching out of KSC is about 57 degrees, or thereabouts. NASA primarily conducts its polar launches by launching southward from Vandenberg AFB, as that takes you straight out over the Pacific Ocean.

EDIT: I did not see that there was a reply on a new page to this topic, my apologies for repeating some of what @mateusviccarisaid :sealed:

Edited by Razgriz1
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On 6/13/2021 at 12:32 AM, Razgriz1 said:

You can always reach an orbit with a higher inclination than your launch site, no matter where that launch site is located. You cannot reach an lower inclination orbit than your launch site, unless you do something like a dogleg maneuver during the launch.

The angle you aim at for any given launch depends entirely upon what kind of orbit you need to target for the mission you're flying. If you have a target inclination in mind, then you can calculate your Launch Azimuth to figure out what angle you need to be aiming toward.

All that being said, NASA does not launch polar missions from Cape Canaveral. This isn't because they can't from an orbital mechanics perspective, but rather doing so would require overflying the northeastern US or Cuba and South America. The maximum inclination typically achieved when launching out of KSC is about 57 degrees, or thereabouts. NASA primarily conducts its polar launches by launching southward from Vandenberg AFB, as that takes you straight out over the Pacific Ocean.

EDIT: I did not see that there was a reply on a new page to this topic, my apologies for repeating some of what @mateusviccarisaid :sealed:

To be fair, none of you answered me. I mean you both gave me a lot to read which I'm thankful for. But I was technically just asking how to aim to the Moon from Cape Canaveral in game.

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4 hours ago, Sesshaku said:

To be fair, none of you answered me. I mean you both gave me a lot to read which I'm thankful for. But I was technically just asking how to aim to the Moon from Cape Canaveral in game.

Ah I had not seen that you were asking about the Moon a few posts prior. You can sometimes launch pretty closely to the orbital plane of the Moon, it just depends. If you feel like doing a little bit of math, you can work out roughly where the Moon will be at the end of a transfer orbit, and then plan a launch window such that your AN/DN lines up with this point, and then perform your TLI such that you arrive at the moon at your AN/DN (roughly speaking, since you don't really "arrive" at the moon in N-body orbital mechanics). This is what the Russians had to do when launching to the Moon since their launch sites are too far north to launch into the plane of the Moon. You don't have to be exact, as you can make small trajectory changes once you're on your way, but you want to at least be in the ballpark. Fortunately the Moon's orbit is slow enough that it doen't move a ton over the course of your trans-lunar orbit.

Here is a pretty interesting webpage explaining some of the considerations NASA had to make when choosing launch windows for the Apollo Program.

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5 hours ago, Sesshaku said:

To be fair, none of you answered me. I mean you both gave me a lot to read which I'm thankful for. But I was technically just asking how to aim to the Moon from Cape Canaveral in game.

To the moon, from Cape? Just head straight 90 degrees west when the launch site intersects the moon's orbital plane (eyeball or use mechjeb). Cape Canaveral is basically on the same inclination as the moon. That's one of the reasons it was chosen for the Apollo program.

Edit. Razgriz1 has beaten me now.

Edited by mateusviccari
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Go to 20:10 in the video.

This is the bug I am facing. The burn indicator doesn't decrease the delta v required for the maneuver.  Is there a fix? Please help...

And which tutorials would you recommend me to learn principia from? I did a fly-by with mun just by the tutorial above, but I don't think this is too much of an in-depth guide...

Edited by theleg
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Posted (edited)
56 minutes ago, theleg said:

This is the bug I am facing. The burn indicator doesn't decrease the delta v required for the maneuver.  Is there a fix? Please help...

And which tutorials would you recommend me to learn principia from? I did a fly-by with mun just by the tutorial above, but I don't think this is too much of an in-depth guide...

This is not a bug, this is how Principia manœuvre execution works: see https://github.com/mockingbirdnest/Principia/wiki/Concepts#flight-planning-user-interface.

Quote

Note that, unlike stock KSP, the Δv counter next to the navball doesn't count down as you burn, and the manœuvre marker does not move. This is because that countdown is only useful as guidance for burns that are modelled as instantaneous (as in stock KSP), but in Principia burns are applied continuously. In order to execute a manœuvre you have to either take a look at the times in the flight plan editor (a countdown to ignition is provided, followed by a countdown to cut-off), or take a look at the shape of the prediction (which should change to become similar to the flight plan) and control your burn accordingly.

With Principia, manœuvre execution is either closed-loop by hand (look at map view, cut the engine when the trajectory does what you want), or open-loop based on the countdowns given in the flight plan (this latter approach is hampered by spool-up times in RO though, so it is better to keep an eye on map view).

Note that MechJeb has an implementation of the timing-based approach (an « Execute next Principia node » button) since around the time of Fuchs (May 2020).

Quote

And which tutorials would you recommend me to learn principia from? I did a fly-by with mun just by the tutorial above, but I don't think this is too much of an in-depth guide...

I don’t think we have much in the way of guides beyond what is on the wiki and the odd video. On the other hand, you may wish to ask questions on the Discord/IRC/matrix channel listed in the OP, there is a fairly active community there.

Edited by eggrobin
typo
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10 minutes ago, eggrobin said:

This is not a bug, this is how Principia manœuvre execution works: see https://github.com/mockingbirdnest/Principia/wiki/Concepts#flight-planning-user-interface.

With Principia, manœuvre execution is either closed-loop by hand (look at map view, cut the engine when the trajectory does what you want), or open-loop basded on the countdowns given in the flight plan (this latter approach is hampered by spool-up times in RO though, so it is better to keep an eye on map view).

Note that MechJeb has an implementation of the timing-based approach (an « Execute next Principia node » button) since around the time of Fuchs (May 2020).

I don’t think we have much in the way of guides beyond what is on the wiki and the odd video. On the other hand, you may wish to ask questions on the Discord/IRC/matrix channel listed in the OP, there is a fairly active community there.

Thanks a lot for taking your time to reply, just to let me know! And thanks a lot for making this mod! 

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On 6/9/2021 at 9:08 PM, eggrobin said:

 See the change log for more details.

no (in game) KSP crashes for two weeks ;-)  @pleroy thank you very much for implementing a way ( #2922 ) to ignore those trouble causing debris 'vessels'.  Thank you both for all the improvements especially the past year.  And to clarify, is it expected that all the enhancements up through Principia Gröbner will apply to any 'older' save created post "del Ferro" (which is the last time I recall it being mentioned that a new save was needed) the same as if I recreated what I was working on in the 'older' save(s) in a new Gröbner save?

Edited by AloE
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6 minutes ago, AloE said:

And to clarify, is it expected that all the enhancements up through Principia Gröbner will apply to any 'older' save created post "del Ferro" (which is the last time I recall it being mentioned that a new save was needed) the same as if I recreated what I was working on in the 'older' save(s) in a new Gröbner save?

Correct, any save created with del Ferro (August 2019) or later should benefit from all the improvements added since then.  Technically any save created with Cardano (March 2017) or later should be readable, but some performance or realism improvements might be missing.

Note that this compatibility code is rather hard to test, so if you run into trouble with ancient saves, please open an issue and give us the save.

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On 6/20/2021 at 4:59 PM, theleg said:

which tutorials would you recommend me to learn principia from? I did a fly-by with mun

Since you already did a Mun flyby, this post has some additional things with which to experiment & also serves as a few suggestions for anyone else new to Principia...

I find it helpful to use pre-created saves & click all the buttons & sliders in various combinations & see what they actually do (and how they affect performance on a given machine).  Here are links to two pre-created saves:

1) The first save has a pre-created flight plan with ~18 minutes until ignition that helps with tinkering with the various transfers in @eggrobin's tutorial at the following link.  I find it to be a good way to get familiar with the dynamics of how the Principia maneuver sliders, plan length slider, & various 'steps' settings change the trajectory plot in the various reference frames:

eggrobin's tutorial: https://github.com/mockingbirdnest/Principia/wiki/A-guide-to-going-to-the-Mun-with-Principia

Here is a link to a folder with a KSP 1.11.2 save made with just Principia Gröbner & FARc.  The save starts in 80k circular equatorial Kerbin orbit.  I also included in the folder the full FARc craft in case anyone ever wants to launch to the parking orbit.  I use it for practice myself, as well as with others.  Practice using RCS translation to adjust the flight path as well as try out Principia time warp physics & spin stabilization along the way.

IhNDwnv.gif

 

zqJJMJ5.gif

 

2) The second is an interesting save posted by @maccollo & is a bit old...I loaded it in KSP 1.11.2 with Principia Green but get a crash when trying to load it with Gröbner.  The save is found at the following thread...yes the ship really does "see" the Mun from a square like path around it...worth loading & flying it just for the view:

869eQMu.png

Also,

  • While learning & especially if using older CPUs like I do...it helps to fly one vessel at a time & remove the *potatoroid* folder found at \GameData\Squad\Parts\Misc\PotatoRoid since asteroids are "vessels".

 

  • KSP Trajectory Optimization Tool use its "Create New Bodies File From KSP" while your Principia save is loaded in KSP with the KSPTOT plugin then load that bodies.ini into KSPTOT for your 'near future' analysis.  Also, load the resulting 'bodies file' in a text editor to see the orbital elements (especially the inclination & Longitude of ascending node (raan)) for each of the celestials which can help with 'close enough' plane alignment like mentioned above (for more complex investigations make sure to use the KSPTOT pre-release 1.6.8.x & read especially KSPTOT pages 179 & 178 for key details):
    8SpaNll.png yjJmWvX.png

 

  • Example Duna & Minmus Transfers: see  dates & dV as example ballpark starting points for practicing & experimenting with approximations of such transfers...
ZrmTlel.png 2DiHDRv.png

 

Edited by AloE
added Principia time warp physics gif, Duna transfer example, Orbit analysis image
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Hello,

at first i want to say big thanks to authors of Principia, because it is realy impressive piece of work (and all related math documents are perfect for study).

Well, but my question is about Principia with last big update of KSP to version 1.12.0. Im not able load KSP anymore and i found, that this happens because of Principia. When i remove Principia form GameData folder, game loads as usualy. With Principia it stays jammed shortly after start of loading and last i see is message "Loading Part Upgrades". I don't see any notes about issue like this there in forum or between github issues.

So my first question is if this is known problem and i just need to wait for fix, or am i only person with this problem and i have some trouble in my game installation?

Edited by JeromeHeretic
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3 hours ago, JeromeHeretic said:

Im not able load KSP anymore and i found, that this happens because of Principia.

Principia is very specific with game versions. If the version number is not exactly the same as a supported one, it will crash the game.
You'll simply have to wait until the proper update is out.

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Ah yes, as you wrote it i remember, that long time ago i did this trick, but it is long time ago.

But now, when i try override config check result is the same as in my previous post.  So, is it working to you with 1.12.0, when you override config check or not? I can live with version 1.11.2 and wait for principia fix, no problem with that, but i'm not sure if its problem in my installation or not.

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Greetings! I have been playing around with Principia for some time and I'm absolutely amazed by the sheer complexity of this mod and what possibilities it brings to the gameplay.

However, my eyeballed maneuvers barely do any justice to the precision and complex math behind these orbits, so I have a few questions to devs and/or someone who attempted the same thing:

  1. What software did you use while developing Principia to validate it's behavior? For example to check that the same initial conditions lead to the same orbits after N seconds, etc.
  2. Did you debug Principia by restarting KSP after every change or you had some other environment to tackle with physics simulation (C++ core) that would visualize orbits without KSP?

Basically I wonder if it is possible to create playground where I could programmatically enter a flight plan and see/analyze resulting orbit in our solar system (either with Principia core or some other software that does similar job).
I don't have required physics/math background for that sort of things but it will be interesting to at least try to make something like a trajectory optimization tool mentioned above or automatic gravity assist planner. Maybe some RPC to Principia are possible?

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On 6/26/2021 at 5:35 AM, JeromeHeretic said:

Ah yes, as you wrote it i remember, that long time ago i did this trick, but it is long time ago.

But now, when i try override config check result is the same as in my previous post.  So, is it working to you with 1.12.0, when you override config check or not? I can live with version 1.11.2 and wait for principia fix, no problem with that, but i'm not sure if its problem in my installation or not.

It's because mods with native C++ dlls now crash KSP load process if the dll resides in gamedata.  Pleroy will need to move the native C++ folder to somewhere outside gamedata.  The paths are presently hardcoded to GameData so it will require devs to fix it in the code.

I have a manually patched version that gets around this, and works in 1.12.0.  Contact me if you want it, under the understanding that you absolutely must not bug official Principia channels with any issues from it.

 

Edited by R-T-B
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2 hours ago, R-T-B said:

 It's because mods with native C++ dlls now crash KSP load process if the dll resides in gamedata.

OMG, this is so stupid!  Changing the path where we look for the C++ DLLs is easy enough, but this is going to be a support headache: "just drop the archive in GameData" won't work and users will get utterly confused.

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1 hour ago, pleroy said:

Changing the path where we look for the C++ DLLs is easy enough, but this is going to be a support headache: "just drop the archive in GameData" won't work and users will get utterly confused.

You can likely work around that by having the dlls having another extension instead of *.dll

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3 hours ago, R-T-B said:

I have a manually patched version that gets around this, and works in 1.12.0.  Contact me if you want it, under the understanding that you absolutely must not bug official Principia channels with any issues from it.

 

3 hours ago, R-T-B said:

Understand, this patch is absolutely without any warranty and authors don't know what you changed, so no support for that patch. Yes, i like to have it (untill official patch for 1.12.0 will be released). But i can't send you a private message, because i'm new member (in fact i registered only because this questions about principia, usualy when i have problem i found answers in proper thread, until now) and i need more posts before private messages are allowed. So please, send me PM (this i can read).

 

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22 minutes ago, Gotmachine said:

You can likely work around that by having the dlls having another extension instead of *.dll

This is also a possibility.  Unsure if the .so extensions need similar treatment or not.

Edited by R-T-B
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9 hours ago, R-T-B said:

 

It's because mods with native C++ dlls now crash KSP load process if the dll resides in gamedata.  Pleroy will need to move the native C++ folder to somewhere outside gamedata.  The paths are presently hardcoded to GameData so it will require devs to fix it in the code.

I have a manually patched version that gets around this, and works in 1.12.0.  Contact me if you want it, under the understanding that you absolutely must not bug official Principia channels with any issues from it.

 

Are the 1.12 work around dlls still available?

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24 minutes ago, Einstein_Cross_X1 said:

Are the 1.12 work around dlls still available?

Yes.  I will send you a PM.

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On 6/27/2021 at 7:05 PM, pleroy said:

this is going to be a support headache

yes...how you guys keep up with & manage all the details amazes me...

& an update for my prior post, apparently I did not notice the engine model changes apparently from the era of1.6, oh dear...lol...despite editing it in 1.11.2 before making the save I just shared in my recent post...appears that 1.11.2 still supported a deprecated model version (heck...I liked the version with the glittery gold insulation) that is no longer found in 1.12!...arghhh...I just revised the craft & updated it in the folder as Principia2MunV5.craft.  I will also need to eventually remake the save again for it to also look proper in 1.12.x...oh well, now at least KSP 1.12.x is the 'final' major KSP version.  So, apparently, a 1.12.x word of caution to anyone else who liked the glittery gold terrier in their older crafts...

interesting that time warp hides the gap...

old craft rebuilt in KSP 1.11.2, looks like somehow I still applied a deprecated version of the LV-909 "Terrier" Engine model that no longer appears in KSP 1.12
qSOVB3a.gif rF3ucwk.gif
Edited by AloE
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has anyone else been experiencing, what i can only call, a slow speed game crash after playing for 45 minutes or so? the skybox texture begins to flicker for me, then slowly all other textures begin to flicker and go dark. i believe the simulation is still running at that point, but the game crashes if i attempt to change scenes.

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