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[old thread] Trajectories : atmospheric predictions

Youen

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ashcanpete

ashcanpete

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Hi,

Thanks for all your work on this great mod. The accuracy is quite a bit off for me with the latest FAR (v0.15.5.4 'Hoerner') and the latest Trajectories. Even using a simple command pod and heat shield, the mod constantly overshoots my actual landing site (I land far short of the prediction). Once, I touch the atmosphere, i can watch the red cross drifting constantly shorter and shorter. I made sure to check the Retrograde box and I hold that AoA during reentry. I'm not sure if I'm doing something wrong, I can post an example ship if needed, but I have this issue on multiple very simple command pod setups. Any help would be greatly appreciated.

Maybe I should also mention I'm using the latest KSP (1.0.99). I figured that since FAR is still controlling the aerodynamics, that shouldn't matter, but possibly I'm wrong.

Edited by ashcanpete
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Youen

Youen

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I don't know for inaccuracies, from your description it seems you are doing everything right. Can you just tell me what is that 1.0.99 version? Is it some kind of pre-release? Because I don't see it in the KSP store.

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politas

politas

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On 06/01/2016 at 6:19 AM, Youen said:

I don't know for inaccuracies, from your description it seems you are doing everything right. Can you just tell me what is that 1.0.99 version? Is it some kind of pre-release? Because I don't see it in the KSP store.

Not sure what ashcanpete meant, but CKAN uses Max KSP 1.0.99 as a shorthand  representation for any version of KSP that comes out before the expected major 1.1 upgrade, which we know will break many mods. It actually turned out to have limited functionality, since it turned out that 1.0.5 broke an awful lot of mods.

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ashcanpete

ashcanpete

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On 1/6/2016 at 1:19 PM, Youen said:

I don't know for inaccuracies, from your description it seems you are doing everything right. Can you just tell me what is that 1.0.99 version? Is it some kind of pre-release? Because I don't see it in the KSP store.

Sorry, I meant KSP 1.0.5, not 1.0.99, I misinterpreted what CKAN was telling me.

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Kobymaru

Kobymaru

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1 hour ago, JT2227 said:

Is this broken for Stock KSP? It always seems to be off by hundreds of kilometers for me

Not really, I recently did some "super precise" landings on Kerbin and Eve, within 10km. Why don't you tell us your procedure, and maybe we can figure out the problems.

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Svm420

Svm420

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@Youen I believe an update is needed for the latest FAR. I am getting this exception in my log when trying to use the mod. I will post a full log if needed, but that is the exception. Trajectories then does show any impact due to not having the right forces simulated for FAR. I believe the relevant changes in FAR are to this file Thanks! 

[LOG 19:36:34.511] Trajectories: Initializing aerodynamic model...
[LOG 19:36:34.511] Trajectories: failed to interface with assembly FerramAerospaceResearch
[LOG 19:36:34.511] Using stock model instead
[LOG 19:36:34.511] System.Exception: Failed to GetMethod GetCurrentDensity on type FerramAerospaceResearch.FARAeroUtil with types System.Type[]:
method not found
  at Trajectories.Util.GetMethodEx (System.Type type, System.String methodName, System.Type[] types) [0x00000] in <filename unknown>:0 
  at Trajectories.Util.GetMethodEx (System.Type type, System.String methodName, System.Type[] types) [0x00000] in <filename unknown>:0 
  at Trajectories.VesselAerodynamicModel.initFARModel () [0x00000] in <filename unknown>:0

 

Edited by Svm420
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Baleine

Baleine

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On 4/2/2016 at 1:41 AM, Svm420 said:

@Youen I believe an update is needed for the latest FAR. I am getting this exception in my log when trying to use the mod. I will post a full log if needed, but that is the exception. Trajectories then does show any impact due to not having the right forces simulated for FAR. I believe the relevant changes in FAR are to this file Thanks

 

I have exactly the same problem. Same error and trajectories show stock orbits without accounting for atmosphere

 

EDIT

Ok, found the issue. You need to use Ferram Aerospace Research v0.15.5.4 "Hoerner", because Trajectories is not compatible with later versions of FAR.

However, it should not be very hard to fix the issue.

 

Edited by Baleine
Having found the problem
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Baleine

Baleine

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Problem is deeper than thought. I tweaked the code so I don't have the error anymore, but I did not got any better result.

Here is a reentry from mun with periapse @2km, but Trajectories think I'm gonna slip through the atmosphere...

uo7FFGu.png

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Alturen

Alturen

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Hello! I'm having some trouble, can someone advise me?

Specifically, the impact symbol "X" shown on the body (in this case the Mun) keeps drifting as the craft gets closer to the surface, even in body fixed mode. If I aim for a crater, for example, the crater will have moved off by the time I get there. I read that the mod is designed to account for body rotation, so I tried it on a fresh 1.0.5 KSP install with no other mods, and the same thing happened. Could it be a Linux issue? (I'm on Ubuntu 14.04).

Thanks! =)

Edit : WAIT!  *forehead smack*  I used hyperedit to get to the mun on that install.. that's a mod. And the problem in my first install happened when I used the simulation option of Kerbal Construction time to test a craft in orbit of the mun. And I just confirmed that the X does not drift when I travel normally to the Mun...

So I suppose tajectories may not work if you teleport to the body directly. PSA! I guess.. Sorry for the bother =D

Edited by Alturen
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MattQGamingHD

MattQGamingHD

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I'm around Bop and i am trying to set co-ordinates for the Kraken but i can't seem to find a way to lay the co-ordinates out because it says to add commas between them, I've added commas and it still doesn't work. So could you tell me how i would layout the co-ordinates for a landing so it gives me the marker for the target landing.

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Spheniscine

Spheniscine

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On 1/5/2016 at 7:13 AM, ashcanpete said:

Hi,

Thanks for all your work on this great mod. The accuracy is quite a bit off for me with the latest FAR (v0.15.5.4 'Hoerner') and the latest Trajectories. Even using a simple command pod and heat shield, the mod constantly overshoots my actual landing site (I land far short of the prediction). Once, I touch the atmosphere, i can watch the red cross drifting constantly shorter and shorter. I made sure to check the Retrograde box and I hold that AoA during reentry. I'm not sure if I'm doing something wrong, I can post an example ship if needed, but I have this issue on multiple very simple command pod setups. Any help would be greatly appreciated.

Maybe I should also mention I'm using the latest KSP (1.0.99). I figured that since FAR is still controlling the aerodynamics, that shouldn't matter, but possibly I'm wrong.

Hm yes I can corroborate that the current version of Trajectories + FAR "Hoerner" does tend to underestimate drag at high altitudes.

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Youen

Youen

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On 21/2/2016 at 3:21 PM, MattQGamingHD said:

I'm around Bop and i am trying to set co-ordinates for the Kraken but i can't seem to find a way to lay the co-ordinates out because it says to add commas between them, I've added commas and it still doesn't work. So could you tell me how i would layout the co-ordinates for a landing so it gives me the marker for the target landing.

Looking at the code (haven't used this feature for a while myself), you should enter two numbers separated by a a comma "," or a a semi-colon ";"

The decimal separator is a dot ".", unless there is some kind of weird behavior depending on your system locale, I haven't verified. In this case, maybe for example you could try using a comma for decimal separator, and a semi-colon between the two numbers? Let me know if this works better...

Also, maybe you're trying to enter these coordinates : 

68° 25′ 48″ N 117° 1′ 48″ E

My system only understands decimal angles, so that would be 

68.43; 117.03

You can use this kind of converter if you need (though obviously the map will show you unrelated places on earth, how come we can't select Bop in any good GPS converter?)

On 23/2/2016 at 6:34 PM, FunnelVortex said:

How well does MechJeb work with this? Can this be used to create a maneuver node for MechJeb to execute? 

You can use Trajectories to plan a maneuver node, and then use MechJeb to execute it, that should just work. You won't be able to use MechJeb planning features to automatically create the node though (just create it by hand and adjust until you are happy with the predicted trajectory)

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MattQGamingHD

MattQGamingHD

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31 minutes ago, Youen said:

Looking at the code (haven't used this feature for a while myself), you should enter two numbers separated by a a comma "," or a a semi-colon ";"

The decimal separator is a dot ".", unless there is some kind of weird behavior depending on your system locale, I haven't verified. In this case, maybe for example you could try using a comma for decimal separator, and a semi-colon between the two numbers? Let me know if this works better...

Also, maybe you're trying to enter these coordinates : 


68° 25′ 48″ N 117° 1′ 48″ E

My system only understands decimal angles, so that would be 


68.43; 117.03

You can use this kind of converter if you need (though obviously the map will show you unrelated places on earth, how come we can't select Bop in any good GPS converter?)

You can use Trajectories to plan a maneuver node, and then use MechJeb to execute it, that should just work. You won't be able to use MechJeb planning features to automatically create the node though (just create it by hand and adjust until you are happy with the predicted trajectory)

Thx I understand it now :D

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Kobymaru

Kobymaru

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Hi! What happens very often to me is that the marker is underground. That's either when showing the current impact point or when setting the Target.

I believe, that's because the marker is always on Sea-level, and any terrain above sea level covers it.

 

Would it be possible to implement the marker in such a way, that it is visible all (or at least most) of the time?

 

Also, could you implement a readout for the coordinates of the impact point?

Edited by Kobymaru
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Youen

Youen

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If I remember correctly, I did attempt to set the cross on the ground, not on sea level ; but it doesn't work correctly indeed. Maybe I'll end up adding a fixed offset...

About the coordinates readout, a first step would be to fill the box with the target coordinates when using the "set current impact as target" button, which would also show the syntax that can be used. And someone also asked about displaying the distance between the target and predicted impact, so adding the impact coordinates would make it more complete.

Unfortunately I can't give any estimate about when all this could be done (first priority is to investigate compatibility issues with latest FAR version anyway).

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