[old thread] Trajectories : atmospheric predictions

[Mystique]

180 and -180 should give the same output (especially with version 1.1.3-rc1 which solved a small bug about that). Make sure you set ALL sliders to 180 for retrograde entry though (each slider influences a different altitude). Next version will include more easily accessible "prograde" and "retrograde" preset buttons for convenience and to avoid confusions. Of course, make sure you actually follow what you've planned (keep pointed perfectly retrograde if that's what you've planned). Also, some bug fixes in version 1.1.3-rc1 may help prediction accuracy (mostly for FAR, but some fixes may improve NEAR predictions as well).

At least for Duna seems like things got MUCH better! Thanks, I'll keep testing.

[SanderB]

I'm trying to use this with FAR and in the trajectories settings screen from the map it says it doesn't recognize the aerodynamics model. Is there something I can do to fix it? I have version 1.1.3 and Mechjeb.

[Rosco P. Coltrane]

Holy mother of Jesus! I don't know how I played KSP without this mod. Hat's off to you, Kobymaru.

On another note, sometimes you get a little too much information:

That's even bigger than the Jool system there.

[Exitalterego]

That's some very pretty space art you have there Rosco

Luckily, you can easily get rid of it by toggling the body-fixed option to off in the Trajectories settings. That will make it a lot more usable

[Youen]

Body-fixed mode is great for landing where you want on bodies without atmosphere (you see the trajectory you'll have after each maneuver node relatively to the rotating body, so it's easy to set a vertical descent exactly above your target). It has other uses, such as adjusting a geostationnary orbit, flying above or under contract waypoints (works great with and without atmosphere), etc.

But for general orbits, and especially excentric orbits, it just doesn't make sense, so as Exitalterego said, you can just turn it off to display trajectories in the inertial frame of the body (as KSP does for all its orbits).

When you see something similar to your screenshot, it's often an under-sampled spiral (if your vessel is far away from the rotating body, it almost doesn't move while the body is rotating, so its trajectory relatively to the body is a spiral, but as only a few points are sampled on that spiral and straight lines are drawn between points, you end up with a big mess).

- - - Updated - - -

I'm trying to use this with FAR and in the trajectories settings screen from the map it says it doesn't recognize the aerodynamics model. Is there something I can do to fix it? I have version 1.1.3 and Mechjeb.

That's weird, I never heard of such a behavior before. What version of FAR did you install (and can you confirm FAR is actually loaded and working as intended in the game?) The KSP log could help troubleshoot the issue (KSP_Data/output_log.txt )

[SanderB]

Actually i figured that I had an outdated version of FAR and that's why it didn't work. Now with FAR 1.4.6 it works.

[FreeThinker]

Question : I would like to use the Trajectrories API to calculalte drag of a vessel just above the athmosphere. What are the License requirements to use the API?

[Youen]

Question : I would like to use the Trajectrories API to calculalte drag of a vessel just above the athmosphere. What are the License requirements to use the API?

The whole mod is under MIT license (see the first post at the bottom there is a link), so you can use it freely, you just have to include a copy of the license if you redistribute source code. This applies to the mod code and the API as well.

I guess it's just a formulation issue, but I don't see what you want to do (calculate drag *above* the atmosphere?).

[SaturnV]

Anyone think that those white & red lines are too thick than the stock trajectory lines?

[Superfluous J]

Anyone think that those white & red lines are too thick than the stock trajectory lines?

They have to be thicker than the stock lines or they'd not be as noticeable. When you have them on, you obviously want to see them. I leave them off until I want to know where my landing spot is or how my aerobraking will go.

[undercoveryankee]

The whole mod is under MIT license (see the first post at the bottom there is a link), so you can use it freely, you just have to include a copy of the license if you redistribute source code. This applies to the mod code and the API as well.

I guess it's just a formulation issue, but I don't see what you want to do (calculate drag *above* the atmosphere?).

Real atmospheres don't have a hard cutoff altitude, so spacecraft in low orbits experience drag that causes gradual orbital decay and have to periodically "reboost" to the desired orbit. Parts of the Trajectories code could be useful to simulate the proper amount of decay.

[Kobymaru]

Real atmospheres don't have a hard cutoff altitude, so spacecraft in low orbits experience drag that causes gradual orbital decay and have to periodically "reboost" to the desired orbit. Parts of the Trajectories code could be useful to simulate the proper amount of decay.

For stock drag, this might work (until 1.0 of course), but if you want to use FAR, this won't work because the mod calls the FAR code directly. If you're above the atmosphere, FAR will think there is no air and will return no forces. If you really want to do that, I suggest you dig into FAR (FARBasicDragModel.RunDragCalculation() and FARWingAerodynamicModel.CalculateForces() ) and see if you can tweak or patch it to return forces for above the atmosphere cutoff.

[Narval]

Can you add apoapsis marker to aerobraking trajectory, it will be very nice for precission flight.

Waiting for 1.1.3 released version, what works with FAR.

[Kobymaru]

Waiting for 1.1.3 released version, what works with FAR.

It has been released in KerbalStuff and CKAN for a while, and I just uploaded it to my GitHub releases page.

[KerbMav]

Real atmospheres don't have a hard cutoff altitude, so spacecraft in low orbits experience drag that causes gradual orbital decay and have to periodically "reboost" to the desired orbit. Parts of the Trajectories code could be useful to simulate the proper amount of decay.

I remember that there already was a mod that did exactly this, no?

Edit: At least the decay part seems to work according to a post in this thread.

http://forum.kerbalspaceprogram.com/threads/70881-0-25-Orbit-Manipulator-Series-(Updated-March-12-2014)

Edited February 4, 2015 by KerbMav

[Hyratel]

is it possible to get a non-map view of the landing site? I got this with the intent of using it for pinpoint science contract missions, but it's dangerous to go into map mode when you're making 3 km hops on minmus

[Superfluous J]

is it possible to get a non-map view of the landing site? I got this with the intent of using it for pinpoint science contract missions, but it's dangerous to go into map mode when you're making 3 km hops on minmus

Both Navhud and In-Flight Waypoints make finding those waypoints a breeze. I've never used Navhud's waypoints because In-Flight's are so awesome.

[Kerbas_ad_astra]

Both Navhud and In-Flight Waypoints make finding those waypoints a breeze. I've never used Navhud's waypoints because In-Flight's are so awesome.

I don't think that's what Hyratel is asking -- those are the goals to be reached (and In-Flight Waypoints is certainly good at showing them), but (I gather that) Hyratel wants to see the actual landing spot.

[hab136]

I don't think that's what Hyratel is asking -- those are the goals to be reached (and In-Flight Waypoints is certainly good at showing them), but (I gather that) Hyratel wants to see the actual landing spot.

Yeah, like this:

(Video taken from the first post, on the "wishlist" items - so apparently the devs know about it)

[Rakh]

The imgur slideshow on the original post shows this mod working on the Mun (where it would adjust for rotation but, obviously, not atmospheric drag).

In practice, I can't get that to happen. The mod just doesn't do anything at all when I'm orbiting a body without an atmosphere. Was this feature removed, or am I missing some toggle I don't know about?

[Tank Buddy]

First of all, I would like to thank you for making this mod. It is such a help.

My install of Trajectories does not display the impact location on airless bodies. Is there a setting I'm missing? I have re-downloaded it from Kerbal Stuff but I'm not getting any different results.

[sashan]

Would be nice to simulate parachutes. Whel landing on Duna they are usually deployed at around 400m/s, the craft is flying almost horizontally. Would make a big difference to landing point.

[Youen]

The imgur slideshow on the original post shows this mod working on the Mun (where it would adjust for rotation but, obviously, not atmospheric drag).

In practice, I can't get that to happen. The mod just doesn't do anything at all when I'm orbiting a body without an atmosphere. Was this feature removed, or am I missing some toggle I don't know about?

My install of Trajectories does not display the impact location on airless bodies. Is there a setting I'm missing? I have re-downloaded it from Kerbal Stuff but I'm not getting any different results.

On some bodies, there is a bug that hides the red cross below the ground. You can turn on "body-fixed mode" that will display the whole trajectory relatively to the rotation frame of the body, which means where the trajectory intersects the body really shows where you'll hit the ground. Be sure to disable it when you don't need it, it would give weird results if you are in higher orbits.

With this option enabled, you can place maneuver nodes, and adjust for a vertical descent exactly above the point you want to go (I find this is the easiest way to precisely reach a point on a rotating body, but maybe not the most fuel efficient I don't know). You'll notice the node is not exactly placed on the trajectory, because of the rotation offset, but you can still adjust it and see the results.

[sashan]

One question - would it work on .25? If not, which version would? I can't run .90 till I get a new PC... My current one is ancient krap.

[Youen]

One question - would it work on .25? If not, which version would? I can't run .90 till I get a new PC... My current one is ancient krap.

Latest version uses specific 0.90 API, so it won't work on 0.25.

You can see compatibility on Kerbal Stuff in the changelog. v1.0.0 is the last for 0.25.