[old thread] Trajectories : atmospheric predictions

[Starwaster]

Earth is about 10 times bigger than Kerbin, so you should translate 6km to 60km if it was in real life (to keep proportions with the planet size, but that's biased since Kerbin's atmosphere is not to scale). That's still acceptable compared to your examples though. But they had to deal with real aerodynamics, wind, etc, while FAR is "just" a "simple" simulation, of which we even have source code. Also, that's for forward simple pod entry, but I get awful results for backward entries at this time (35km or more for a simple rocket), something must be wrong somewhere. It gets worse with deadly reentry shields, but I don't know yet if it's just the same bug that has exagerated results, or if there is some sort of incompatibility with DR.

I don't think its size necessarily translates linearly, or that Earth was in any of our examples.... (RSS?)

As far as Deadly Reentry, it has no effect on aerodynamics so I'm not sure why it would be affecting your results, unless you were testing non-stock aerodynamics, in which case ablative shielding can lose significant amounts of mass during reentry as the shield boils away. (IRL I think it would lose a lot less since most of it is still there, just charred). Anyway, for non-stock aero, lower mass means lower inertia. That could alter your prediction quite a bit couldn't it? Did you try it with stock aero?

Oops I guess I should refresh on a screen that's been sitting there for a day before I reply, yes?

[O Nerd]

Oh, no 0.23.5 support. ;-;

[TheGamingNoobster]

I Found this happening on Minmus

http://imgur.com/a/F6Fsb#0

[Starwaster]

I Found this happening on Minmus

http://imgur.com/a/F6Fsb#0

Holy crap it's a working Spirograph in KSP!

[Youen]

Holy crap it's a working Spirograph in KSP!

Yeah, that's a feature of course, not a bug ;-)

Hmm, ok, it's just the space orbit display that doesn't have enough points at this time (so it draws straight lines between points sampled at huge distances on the trajectory). Also, disabling body-fixed mode should help, as it doesn't make much sense in this situation (it's mostly useful when on a low orbit, for entry, or when flying in atmosphere)

[mulldogs]

Are there particular benefits of integrating in Blizzy toolbar, more than the stock toolbar ? (that's a real question, I find the stock toolbar works just fine for me, but maybe with lots of plugins or I don't know whatever reason you could have)

I just find Blizzy toolbar is less intrusive and smaller than stock as i like just having my fuel read out on the right and all my mod read outs pop up under the left when needed. Just personal preference but I like the way chatterer has made it easy to use both or either with a simple setting in the GUI

[sarbian]

I think you have an other minor source of error. You don't check for Part.PhysicalSignificance, so the few part that have the flag report mass while the game does not use it.

You should ignore any part with p.physicalSignificance == Part.PhysicalSignificance.NONE for mass and stock drag (you'll have to look at ferram4 code for FAR/NEAR, I don't remember how he handles them from memory).

Edit : and +1 for blizzy toolbar as an alternative. You can use the wrapper to use it without even having to to reference his lib.

Edited October 1, 2014 by sarbian

[Youen]

I think you have an other minor source of error. You don't check for Part.PhysicalSignificance, so the few part that have the flag report mass while the game does not use it.

You should ignore any part with p.physicalSignificance == Part.PhysicalSignificance.NONE for mass and stock drag (you'll have to look at ferram4 code for FAR/NEAR, I don't remember how he handles them from memory).

Edit : and +1 for blizzy toolbar as an alternative. You can use the wrapper to use it without even having to to reference his lib.

OK, I'll fix that physicalSignificance thing. Any example of such a part, so that I know if I've already encountered the case without knowing ?

By the way, don't know if you've seen the TrajectoriesAPI library, don't hesitate to tell me if you need other things exposed, in case you would want to use it (which applies to everyone of course).

[Youen]

I've added the mod on Kerbal Stuff (exactly the same version as is already available on GitHub of course)

[sarbian]

Any part with a ModuleLandingGear will have the flag outside the VAB launch. And any part with PhysicsSignificance = 1 in their cfg which are mostly small parts like the various structural Strut, the antennae, the O-10 MonoPropellant & Vernor Engine engine and a few other misc part. Most are quite light so the impact is small, but it did improve MJ landing sim by a couple of meters.

I don't know if I'll use the provided API. MJ does have a working drag sim for landing and it also supports parachute and calculate an optimal time to open them and land where we want to. What is missing is the FAR/NEAR stuff, and eventually the stock lift. It also work in a thread, so it can't really call something not sync with it.

When I have more free time to code I'll most likely ask if I can borrow some ideas and code to use them in MJ itself.

Speaking about stock lift, that reminds me of something. Did you know about ModuleAerodynamicLift & ModuleControlSurface CalculateForce method ? It's what you need to get stock lift force.

[Youen]

Did you know about ModuleAerodynamicLift & ModuleControlSurface CalculateForce method ? It's what you need to get stock lift force.

OK, didn't know that, it should help, thanks :-)

[How2FoldSoup]

This looks awesome! I'm downloading right now...one question though. Is there IVA usability or are there any plans to integrate glideslope infos or some info into an IVA screen via RPM? I think it would be awesome! Especially for b9 cockpits.

[Youen]

This looks awesome! I'm downloading right now...one question though. Is there IVA usability or are there any plans to integrate glideslope infos or some info into an IVA screen via RPM? I think it would be awesome! Especially for b9 cockpits.

Not at this time, but as it was already requested before, I just added it in the feature requests

[Entropius]

In the latest version, I noticed 2 things happening: (1) Laggy performance on the Map View and (2) My debug log was getting spammed with orange text messages like “Mesh.vertices is too small. The supplied vertex array has less vertices than are referenced by the triangles array.â€Â

Removing the mod appears to make the problem go away, so I'm pretty sure it's Atmospheric Trajectories at work. Also worth noting, that disabling the trajectory drawing option via the toolbar button didn't stop the symptoms.

[Youen]

In the latest version, I noticed 2 things happening: (1) Laggy performance on the Map View and (2) My debug log was getting spammed with orange text messages like “Mesh.vertices is too small. The supplied vertex array has less vertices than are referenced by the triangles array.â€Â

Removing the mod appears to make the problem go away, so I'm pretty sure it's Atmospheric Trajectories at work. Also worth noting, that disabling the trajectory drawing option via the toolbar button didn't stop the symptoms.

I already noticed that vertex issue message (I don't think it's related to the latest version), but it doesn't happen all the time, and so far I don't know when it happens or not. I haven't investigated further yet. Added on the bug tracker, for what it's worth, as I won't have time to work on that for a few days.

[Starwaster]

I already noticed that vertex issue message (I don't think it's related to the latest version), but it doesn't happen all the time, and so far I don't know when it happens or not. I haven't investigated further yet. Added on the bug tracker, for what it's worth, as I won't have time to work on that for a few days.

And here I was blaming KW Rocketry's engines....

[Youen]

I've updated the first post (shorter description, and user manual). Let me know if something is not clear or missing.

[LostOblivion]

This rocks!

Requests: I think you should drop the thick white line until you enter the atmosphere (it should remain blue until then), then it would turn red (like now), and then it would turn white (like now). Also, I think the lines are a bit thick. A thinner line to match the regular orbit lines would be preferable I think.

Another thing. I usually reenter using pods and notice the small black circle dot is usually opposite from where it should be to correct the reentry. This is at a 180 AoA.

[Youen]

Yes, other people have requested the same thing (not displaying trajectories until it diverge from the stock one), it's already in the feature requests.

I haven't tested guidance for a 180° AoA, it may indeed be reversed. Or maybe this comes from the pod shape that doesn't behave like a wing (positive angle would go down instead of up?). Guidance on the nav ball is mostly targeted as space planes (for which a very small change in AoA results in a big change in landing position). Anyway, that's now added in the bug tracker (but the rate of bug reports is currently way higher than bug fixes ;-))

[Akira_R]

This rocks!

Requests: I think you should drop the thick white line until you enter the atmosphere (it should remain blue until then), then it would turn red (like now), and then it would turn white (like now). Also, I think the lines are a bit thick. A thinner line to match the regular orbit lines would be preferable I think.

Another thing. I usually reenter using pods and notice the small black circle dot is usually opposite from where it should be to correct the reentry. This is at a 180 AoA.

Did you make sure to set the AoA to 180 on all the sliders on the GUI in the map screen?

[LostOblivion]

Yes, but a simple workaround is to point the nose opposite of the black circle. So if it says 1 % up, you point it 1 % down, etc.

[Niemand303]

Srandart Update Question #1: Any compatibility issues?

[Crimor]

God damn, why haven't I seen this before now, keep up the awesome work.

[Youen]

Srandart Update Question #1: Any compatibility issues?

You mean with KSP 0.25 ? I haven't tested yet, I guess I'll have to recompile and distribute a separate package (I'll keep updating bug-fixes for 0.24 for some time too).

[Smorfty]

God damn, why haven't I seen this before now...

because it's fairly new