[old thread] Trajectories : atmospheric predictions

[atomicfury]

Well blizzys toolbar dissapears when you go into mapmode. I just installed the latest version of trajectories and I still do not have a menu or a GUI.

Make sure you have the latest toolbar. Also watch out that toolbar moves when you go into mapmode - you'll have to hunt down where it appears and turn on the Trajectories button.

[Youen]

Well blizzys toolbar dissapears when you go into mapmode. I just installed the latest version of trajectories and I still do not have a menu or a GUI.

Maybe a bug with the toolbar then ? There are a lot of mods that need buttons in map view, no reason for the toolbar to disapear in this view (and it works fine on my computer, I'm using toolbar version 1.7.9). If it's a Trajectories bug that prevents the toolbar to appear in map view, could you look at your KSP_Data/output_log.txt file to search for error dumps? The file is cleared each time you restart the game, so you'll have to start, go in map view, then exit (alt-f4 for example), and check if there is any hint in the file. As an alternative, you could disable blizzy's toolbar integration: edit the file GameData\Trajectories\Plugin\PluginData\Trajectories\config.xml and replace the line "<bool name="UseBlizzyToolbar">1</bool>" by "<bool name="UseBlizzyToolbar">0</bool>" (i.e. replace the "1" by a "0"). This setting can be changed in the GUI, but obviously you'll have to manually edit the file in your case. After that, the button should appear in the stock toolbar.

- - - Updated - - -

Give Waypoint Manager a go. It's easy to save a whole mess of places, and combined with Trajectories it's straightforward to land wherever.

Sounds like a good idea, I'll take a look.

Edited May 25, 2015 by Youen

[Eleven]

Give Waypoint Manager a go. It's easy to save a whole mess of places, and combined with Trajectories it's straightforward to land wherever.

I apologize for going off on a tangent and possibly being OT, but do mean just saving KSC coordinates in WPM, and then just simply lining up a re-entry trajectory to cross over it? Or is there some other more detailed way of doing it with that mod?

[amorymeltzer]

I apologize for going off on a tangent and possibly being OT, but do mean just saving KSC coordinates in WPM, and then just simply lining up a re-entry trajectory to cross over it? Or is there some other more detailed way of doing it with that mod?

For me, yes - I simply can't keep track of where KSC or other points of interest on Kerbin and other spobs are, so a waypoint just helps me find it. I figure it's up to me to aim there and fly/land the bloody thing - that's where Trajectories comes in. I do know that MechJeb's landing assistant let's you pick a spot, so that could be used in conjunction with WPM. Last I heard it didn't work with aero, but perhaps that will be changed soon a la Trajectories.

[PeskyPony]

You should have all the time you want to adjust your aerobraking when you are on the edge of Jool SOI (which is really large), at least it works smoothly for me each time I needed it. You can also predict what kind of maneuver you can do with an aerobrake by putting a node at Jool's Pe to simulate a retrograde burn, which is usually the same as an aerobrake, and see if the new orbit can intercept your target. As atomicfury pointed out, because Jool has such a big gravity well, you are likely to go very fast near Jool, so beware the heat... You might want multiple aerobrakes (I think it's reduces the maximum heat, right?), one to be captured in Jool SoI, another to adjust your orbit?

I'm planning to refactor Trajectories code to cleanly separate aerodynamic models (stock and FAR) as well as the cache system, and use the occasion to allow a different cache for each planet at the same time (currently only one cache is available for the current SOI). Until then, it is indeed a limitation of Trajectories that you can only predict atmosphere entry in your current SOI.

Yes, this is what I'm doing. Placing a node and then playing around with the results. It's just I'm doing a Grand Tour on my first visit to Jool, so I want to save as much fuel as possible, meaning I'd like to be able to correct as far away as I can. Not complaining, since I love the hard work you guys are putting into this. Besides, atmo prediction only inside the SOI is magnitudes better than no prediction at all.

Follow-up, though maybe I should post this in the FAR thread, but if somebody here knows it'd be appreciated: It seems FAR is easier on the CPU than Stock, is that so? The only reason I went back to FAR was because of this mod, but now I'd rather play with whichever gives more FPS.

[StahnAileron]

I've released the new version on KerbalStuff, it should now work with stock aerodynamics (thanks to atomicfury), the bug with other SOI is fixed (it won't predict atmospheric entry until you get in that body SOI, but it won't freeze/lag either), and if you use the latest FAR version (0.15.2) the bug of wings breaking during prediction is fixed as well. So this release should be stable (but as usual, hasn't been much tested before release due to lack of time)

A bit late, but you might want to change the first post to reflect the update. OP/Thread Title is currently v1.2 with stock support still struck out. Considering the fixes done from 1.2 to 1.3, I think people would want to know about the update in a more upfront manner. (I initially only knew about the update because I wanted to look at the change log on Github and noticed the updated version number and "support for stock aero" line.)

[A_name]

A bit late, but you might want to change the first post to reflect the update. OP/Thread Title is currently v1.2 with stock support still struck out. Considering the fixes done from 1.2 to 1.3, I think people would want to know about the update in a more upfront manner. (I initially only knew about the update because I wanted to look at the change log on Github and noticed the updated version number and "support for stock aero" line.)

I had just navigated to the last page of the thread to rant about stock aero not being supported. This is great news!!!

[Youen]

A bit late, but you might want to change the first post to reflect the update. OP/Thread Title is currently v1.2 with stock support still struck out. Considering the fixes done from 1.2 to 1.3, I think people would want to know about the update in a more upfront manner. (I initially only knew about the update because I wanted to look at the change log on Github and noticed the updated version number and "support for stock aero" line.)

I would have, but it's not my thread so in fact I can't. I've just PM'd Kobymaru but no guarantee he'll be arround. Feel free to subscribe to the notifications on KerbalStuff though (at least there we can add multiple developpers to the same mod so anyone can publish updates).

[Sokar408]

Remember to change the title. It still says it only supports FAR

[INSULINt]

Super excited that this has been updated for stock!

[A_name]

Super excited that this has been updated for stock!

Me too! Hopefully this will help me in my efforts to crash an asteroid into KSC!

[Booots]

Me too! Hopefully this will help me in my efforts to crash an asteroid into KSC!

... Wait. What?

On a constructive note, all of my aerobrakings have overpredicted drag so far. I use a simple retrograde pointing and then watch as my predicted orbit slowly grows larger as I go through the atmosphere. I do have a bunch of things in Universal Storage bays and service bays; are you taking into account occlusion for things like that?

[orosee]

I had a problem with landing on Kerbin (stock aerodynamics), I was returning from Mun with a simple vessel, aiming for the pyramids on a very shallow trajectory (the re-entry made 3/4 circumference within the atmosphere) but after setting the prediction crosshair, I still had to use more than 300 m/s dV of remaining fuel to keep the crosshair in spot - it just kept moving "left". This definitely never happened to me before 1.0.x.

Anyway, absolutely GREAT to have it and I'm sure any problems will be ironed out soon.

[Youen]

I had a problem with landing on Kerbin (stock aerodynamics), I was returning from Mun with a simple vessel, aiming for the pyramids on a very shallow trajectory (the re-entry made 3/4 circumference within the atmosphere) but after setting the prediction crosshair, I still had to use more than 300 m/s dV of remaining fuel to keep the crosshair in spot - it just kept moving "left". This definitely never happened to me before 1.0.x.

Anyway, absolutely GREAT to have it and I'm sure any problems will be ironed out soon.

Stock model support is very recent, I wouldn't be surprised if there are (subtle?) inaccuracies or edge cases that are not handled yet. Also, wings are not predicted, so if you have some it would explain the issue. Another thing I've noticed with FAR (don't know how it works in stock) : wing fins make more drag when they are used for steering, which is the case for example if you enable SAS, and I think this has an impact on the landing position, but it's difficult to know exactly what is causing what (bugs, approximations, imprecise orientation, etc.)

[diomedea]

... Another thing I've noticed with FAR (don't know how it works in stock) : wing fins make more drag when they are used for steering, ...

All control surfaces exert a force perpendicular to the surface when invested by airflow also in stock KSP. That way, when they are deflected provide not only the force required for steering, but also a force component opposite to the direction of the airflow, that is the same as drag.

The picture here shows the force (the long yellow lines from the inner wing ailerons, used as flaps) angled backwards.

[Entropius]

Yay stock support! Thanks! Even if wings are causing inaccuracy it's nice to see progress. For what it's worth, my 2 reentry capsules have so far had absolutely perfect accuracy landings. So it's fine for capsules (and assumably vacuum landings).

Just a thought for those who are reporting inaccuracies, I'm wondering if the presence or absence of the Stock Bug Fix mod might be a factor. I seem to remember there being a bug involving the drag caused by landing gear/wheels to be present when retracted, rather than extended.

[Eleven]

Yay stock support! Thanks! Even if wings are causing inaccuracy it's nice to see progress. For what it's worth, my 2 reentry capsules have so far had absolutely perfect accuracy landings. So it's fine for capsules (and assumably vacuum landings).

Just a thought for those who are reporting inaccuracies, I'm wondering if the presence or absence of the Stock Bug Fix mod might be a factor. I seem to remember there being a bug involving the drag caused by landing gear/wheels to be present when retracted, rather than extended.

I have Stock Bug Fix installed, but the few times I've used Trajectories to figure out where I wanted to land (flawlessly so far) I have not had wheels or landing gear on those landers....

[Chittychad23]

None of the parts attach to each other. all they do is fall through the surface.

[Baythan]

None of the parts attach to each other. all they do is fall through the surface.

Does this statement have something to do with Trajectories? This mod does not add, remove, or change any parts, all it does is calculate trajectories through atmosphere and onto the surface of rotating bodies.

If you are having an issue, more information would be helpful.

[Eleven]

None of the parts attach to each other. all they do is fall through the surface.

Does this statement have something to do with Trajectories? This mod does not add, remove, or change any parts, all it does is calculate trajectories through atmosphere and onto the surface of rotating bodies.

If you are having an issue, more information would be helpful.

I've a feeling he just posted in the wrong thread. I also have a feeling as to which thread he *meant* to post in

[cybersol]

Whoaa, I missed that this had been updated for stock. Time to remove FAR only from the title again?

[David H]

Kobymaru

http://imgur.com/gallery/Bo0WY/new

Edited May 31, 2015 by David H

[severedsolo]

I realise this isn't exactly Trajectories fault - but maybe someone can come up with a suggestion.

So you line up your trajectory, then stage leaving just your capsule behind. The landing marker then jumps about 10 - 90 degrees west. Now I appreiciate that this is a result of the vessels drag profile changing, but does anyone have a good rule of thumb as to where to aim your initial marker, if you are going for KSC?

[SanderB]

severedsolo I don't think that's quite possible. I think you'll have to add at least 1 translational RCS port aligned with the CoM and a little onboard monoprop (from the capsule monoprop tank) so you can precisely target your landing once you've staged your capsule. At first you'll want to overshoot the projected landing before staging, but the sensitivity of the mechanics will force you to make some additional adjustments once staged.

[SelectHalfling0]

does this work with heatshields/fairings in stock?