Fairing CoL Offset (also staged)

[KroShan]

At the end of my new Caveman-Career i unlocked fairings. With fairing the launch felt quite different compared to 1.0.5 without and 1.0.4 with fairings. It seems that the payload causes less flips than the fairing even when they are in similar sice and shape. Thats how i found the offset of the bodylift vector. Its allways in front of the fairing no matter how long you build it in the VAB. I am even more concerned as the vector is still drawn when the fairing is staged. But i am not sure if this force is applied also. It is also interesting that the direction of the shown vector is inverted to what one would expect.

KSP Version: v1.0.5.1028 Windows7 32-bit, updated from v1.0.5.1024 (clean install)

What Happens: Center of Lift (bodylift) is applied in front of the fairing. Bodylift is even applied when the shroud is already staged.

Mods / Add-Ons: All Stock

Steps to Replicate:

1) build craft with fairing. launch with aero overlay (F12)

2) deviate craft from prograde.

3) stage the fairing.

Result: Rocket is too fliphappy since the tourque is much higher than it should be. Especially when the fairing is staged there shouldn't be any effect caused by the fairing.

Further investigation:

If you ad

4) toggle Aero Overlay off and on

you can find that the vector of the fairing bodylift is no longer displayed. So maybe the force isn't applied.

Fixes/Workarounds:

- don't use Fairings!?!

- have wings on the backend of the rocket till the craft is above 30 km

Other Notes/Pictures:

- i tried out for 1.25m and 2.5m fairing - same result

- 2 additional screenshots here http://imgur.com/a/nKlNj

Edited November 13, 2015 by KroShan
Introduction, English is tough, what happens, further investigation

[diomedea]

Good find, checked and can confirm. Would rate this a bug, will be reported for action.

[KroShan]

Thx.

I pm'd sal-vager for the "Kerbal Space Program 1.0.5 New Issues Repository." Are you reporting it on the bugtracker?

[sal_vager]

Yeah, well spotted, though hopefully the effect is small as the lift, drag and CoM of the fairing resets to the fairing base when staged, so while the bodymass (that's the cyan line) looks to be offset incorrectly the force should be small, and dropping as air density decreases.

[EdFred]

So I had a similar thread stared in the KSP General discussion which was closed a redirected here. Is this really not going to be fixed until 1.1? This makes the game rather, um useless for rockets at this point. I have KSP on steam - which autoupdated to 1.05 for me. Is there a way to get a prior version back, because this is pretty much a broken version at this point.

[KroShan]

Off Topic:

diomedia wrote in your thread that it may be fixed earlier.

I have KSP on steam - which autoupdated to 1.05 for me. Is there a way to get a prior version back, because this is pretty much a broken version at this point.

I am also looking forward to 1.1, but i think this Version is quite good, nonetheless this may help you.

Edited November 13, 2015 by KroShan

[EdFred]

Thanks. I did the rollback.

[diomedea]

Thx.

I pm'd sal-vager for the "Kerbal Space Program 1.0.5 New Issues Repository." Are you reporting it on the bugtracker?

Yes, reported on the tracker less than 30 mins after my previous post.

[Claw]

After further investigation, there are three bugs going on here.

1) The location of the body lift line before decoupling the fairing is incorrect. It's applying lift force too far ahead of the fairing (i.e. the overlay is correct).

- My StockBugFixes now contain the fix for this in ModuleProceduralFairingFix. (http://forum.kerbalspaceprogram.com/threads/97285)

2) The location of the cyan overlay line after decoupling the fairing is not correct. That is, it's showing the lift too far ahead, but that's an overlay problem. That's not a force position problem.

- Fix for this is to simply cycle the overlay after decoupling (I did not include this fix because it seemed wasteful to spend CPU cycles checking for and fixing the overlay).

3) The direction of the body lift after decoupling is incorrect. The overlay is showing the direction that lift is being applied, which is in an incorrect direction (i.e. the overlay direction is correct).

- This is not limited to the procedural fairings, but is actually a systemic problem in the body lift algorithms. You can replace the fairing with any part that's wider than it is tall (such as a SAS module, or FL-T100), and the incorrect direction of body lift results.

Cheers,

~Claw

Edited November 15, 2015 by Claw

[sal_vager]

Added to the known issues list, this will require work at the developer level but we'll have to use Claws fix for the time being.

[KroShan]

After further investigation, there are three bugs going on here.

...

Cheers,

~Claw

i am a bit proud of my finding and right guessing regarding the forces of the staged fairing

Thanks for the Stock Bug Fix Modules.

[Streetwind]

Out of interest, are these bugs that apply to stock aerodynamics exclusively? I.e. if I installed FAR, would they go away?

Or are the bugs part of modules that FAR doesn't replace, and appear just the same in such a modded install?

[KroShan]

Off Topic

On 18.11.2015, 14:18:35, Streetwind said:

Out of interest, are these bugs that apply to stock aerodynamics exclusively? I.e. if I installed FAR, would they go away?

Or are the bugs part of modules that FAR doesn't replace, and appear just the same in such a modded install?

I haven't installed FAR on 1.0.5 - but i assume that this bug doesn't occur in FAR. The drag model in FAR is based on a voxel rebuilt craft and not on the drag cubes of the parts like in stock.