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What is causing this thing to roll / pitch / yaw?


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So, I established my first station in orbit arround Mun as a hub and I was all happy and began preparing further exploration missions. But as I docked my first lander to push the station into a better orbit with it, I noticed something strange is going on with this thing. Its just not stable at all. It rolls, pitches, yaws into directions that I cant see a pattern in.

It is built symmetrically as good as I could (see pics below). The fuel is symmetrically located in the tanks to both sides. It might be assymetrical somewhere where I cant tell, but what I really dont understand is the fact that the effect even shows without any thrust beeing applied. In fact, I used the time warp to stop any spinning etc., go back to regular time progression and did nothing to it, just watched it... and the effect kicked in, the station started to yaw / pitch / roll.

Without SAS I can watch it spinning. If I activate SAS, it tries to supress the moving, but soon enough it gets out of hand and SAS cant control it anymore.

First I thought it might be the movement to adjust for relative sun position of my many solar panels. So I retracted them. But that wasnt it. I deactivated torque on all mods that have it. Then I figured I might be to close to the Mun and its gravity could have a strange effect. So I pulled 90 km away, but its still spinning. I switched to a different ship and went back. Went to space center. Restarted the game. Nothing seems to help and I cant find the design flaw.

Another ship that is in a very similar orbit (the one I wanted to dock with) has no such problems at all.

Anyone got an idea what could be causing this? Especially the fact its showing up without thrust applied is something I cant make sense of... :(

PS: I did put all the most stupid Kerbels that I could find into the two labs. Maybe they are having a big party inside and keep pushing the thing into random directions? :confused:

EDIT: the only mod I have installed is the Flight Engineer

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Edited by TrooperCooper
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The usual cause of 'spontaneous' forces acting on a ship that way is part-clipping. I can't see anything obvious but that's all I can offer at the moment :-( Some ships are just like that, did you call it Titanic?

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It could be residual wobble. On large crafts or ones with many joins between parts or weak joins like docking ports the whole craft can flex under force. The problem is the bend at each part is so small that it is hard to stop. Any ASAS systems or RCS systems can even make the problem worse as they try and force just one part to be back on target while powering either the part they are in or an opposite end of the cart to wobble more. Try rotating the craft along it's axis with SAS turned off. The effect should prevent too much wobble. If it calms down and you can stop the rotation without reactivation the wobble then this is a temporary fix.

Apart from more struts, I've not found any other fix for this, if it is what you have.

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You said that once you docked something to it, it started getting those forces? If that's true, you might be clipping some part from the second craft into that station. I don't see any part clipping in those pictures, though.

(That is a really nice looking thing, although it's a little bit big. That's not bad, though.)

Try time-warping. It should disable physics. Once you exit time warp, if it continues the craziness, it's part clipping.

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What you are experiencing are most probably phantom forces, remnants of the so called "velocity Kraken" which used to tear apart ships that were moving too fast. Now, at or above 750 m/s absolute speed, a fix kicks in, making ships moving at that speed stable. However, ships that move slower than that are still moving using the old code which introduces random arithmetic errors into motion of individual parts. As a result, ships tend to rotate in random directions.

When you are in Mun orbit, you are moving at about 500 m/s - not fast enough for the "krakenbane" to kick in.

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If it's all stock, post a craft file (or the save file) if you can.

In addition to what Kasuha said, here's a couple extra things to look for, just in case.

- Zero out the trim using ALT+X

- If you have a joystick installed, make sure it's calibrated.

- If you ever had a joystick installed and then removed it, you'll need to delete the configuration.

This spoiler is for a throttle fix, but you can use the same idea if you're unable to zero out the joystick in-game.

Phantom throttle changes when switching docking mode (and you ever had a joystick installed) – [FIX]

Sometimes when you exit docking mode back to staging mode, the throttle will reset itself to something other than 0%.

For some reason (maybe Unity update?) the game will now grab old joystick values, even if it isn't installed anymore.

You can do one of two things:

- Delete settings.cfg and let the game create a clean one (this will delete all of your graphics settings and keybindings).

- Edit the settings.cfg manually using the information below.

What it might say (from settings.cfg):


AXIS_PITCH
{
name = Logitech Freedom 2.4 Axis 1
id = joy0.1
inv = False
sensitivity = 1
deadzone = 0.05
scale = 1
group = 0
switchState = Any
}
AXIS_ROLL
{
name = Logitech Freedom 2.4 Axis 2
id = joy0.2
inv = False
sensitivity = 1
deadzone = 0.05
scale = 1
group = 0
switchState = Any
}
AXIS_YAW
{
name = Logitech Freedom 2.4 Axis 0
id = joy0.0
inv = False
sensitivity = 1
deadzone = 0.05
scale = 1
group = 0
switchState = Any
}
AXIS_THROTTLE
{
name = Logitech Freedom 2.4 Axis 3
id = joy0.3
inv = True
sensitivity = 1
deadzone = 0.05
scale = 1
group = 0
switchState = Any
}
AXIS_THROTTLE_INC
{
name = None
id = None
inv = False
sensitivity = 1
deadzone = 0.05
scale = 1
group = 0
switchState = Any
}

What it should say (clean install, no joystick):


AXIS_PITCH
{
name = None
id = None
inv = False
sensitivity = 1
deadzone = 0.05
scale = 1
group = 0
switchState = Any
}
AXIS_ROLL
{
name = None
id = None
inv = False
sensitivity = 1
deadzone = 0.05
scale = 1
group = 0
switchState = Any
}
AXIS_YAW
{
name = None
id = None
inv = False
sensitivity = 1
deadzone = 0.05
scale = 1
group = 0
switchState = Any
}
AXIS_THROTTLE
{
name = None
id = None
inv = False
sensitivity = 1
deadzone = 0.05
scale = 1
group = 0
switchState = Any
}

- You said you turned off all the torque. Make sure you turn it all off, then timewarp to stop rotation, then drop back to normal. If it turns again, then it's probably clipping or some other bug.

- Another fix that worked for a recent "spontaneously exploding ship" that wobbled itself apart from phantom forces was to transfer some fuel around and change the mass distribution. Perhaps give that a try.

Not sure if any of that will help, but if I think of anything else, I post it.

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  Vanamonde said:
I have not seen it happen myself, but a number of players have reported sourceless rotations while in Mun orbit. Kasuha's explanation for it seems reasonable to me.

Okay, I can confirm this now. Its not just the station that I posted above, its happening to other ships that I have in Mun orbit, too. Its just more noticeable and difficult for the SAS to keep the effect under control on larger units like the station I guess. I'm going to do some more tests with the exact same vessels arround Kerbin orbit, but at first glance it indeed seems like a local Mun problem...

Thanks for all the helpfull input, guys. :wink:

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As said earlier, SAS can make the wobbles worse. Seems like SAS can't handle slow oscillations of heavy craft.

I've found an easy way to stop at least some wobbles, and it's easy.

1) When your craft is not under throttle, engage SAS.

2) Watch the pitch/yaw/roll indicators.

3) When you think that pitch/yaw/roll commands has reached it's maximum and is about to travel in the opposite direction, TURN OFF SAS.

4) Engage SAS again. Pitch/roll/yaw commands will now start from center.

5) If the craft is still wobbling repeat the process. (go to step 2)

Will probably not work if the craft is under influence of phantom forces/kraken but it has worked on many of my heavier craft.

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  MoeMelek said:
Will probably not work if the craft is under influence of phantom forces/kraken but it has worked on many of my heavier craft.

And that is the case, since it does start to move under influence from some magical force even when I come out of time warp with no thrust applied. So its not the problem of getting it under control once. I probably could manually do that. But as soon as I leave the controls alone, it starts again, since *MAGIC FORCE* is pulling on all ships. Makes docking near Mun a real pain right now. Considering on giving up on having a station there. :huh:

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  • 1 year later...
  • 7 months later...

I'm having this issue in 1.0.5 around Minmus. All of my attempts at orbiting have resulted in an inexplicable negative yaw and positive pitch (yaw is as if I am holding A, pitch like I am holding S). Time warping only halts it for a bit, and turning on SAS is like not having SAS on at all (i.e. it doesn't stabilize the ship, although the magic forces go away, too). It affects all of my ships, and is making my science mode game rather difficult. Attached are the screenshot of the probe, along with the ship's save in the persistent.sfs (since the original craft file is huge).

Screenshot:

  Reveal hidden contents

 

persistent.sfs node:

  Reveal hidden contents

Upon inspection of my save, it appears that the vessel had its trim set somehow. However, it is important to note that I never set the trim manually, and this has occurred on three separate occasions. Near as I can tell, there's something about Minmus's SOI that causes trim to be set. Tellingly, this is the only body that I have had problems with thus far (I obviously haven't gone to any other planet like Moho, seeing as I had to use a Small Circular Intake as a nosecone). Anybody else have any ideas?

P.S. I run KSP on Linux 64-bit. The only mod I have in this install is Kerbal Engineer Redux (for 1.0.4, but it still works). I'll probably try without it, just to see if that fixes the problem.

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