SAS Bug

[Viper31st]

built a ship, with a command-capsule for 3 kerbals (one pilot, one technician, one scientist), launched it, and directly after lift-off, the problems began...started to spin, had massive problems to keep it under control, after some sweaty minutes, i reached space, i tried to burn an orbit, but it don´t work, cause i had to correct the ship permanently, was absolute unflyable.
at building my ship, i installed 3 gyros, to make sure, i had enough momentum in space, cause this thing was heavy.

any idea?

i´ve had this problem since 2-3 days ago. normally i would restart KSP and load my last safe-game, after reloading KSP it works, as it should, but now....i am very frustrated....

[Chibbity]

Did you actually turn SAS on? "T"

[Viper31st]

yes i did....my pilot did an EVA and enters the capsule again, but didn´t get better...same problem, after saving my game, and restarting KSP, for a short time, SAS worked as it should, after that, it didn´t work....what the hell is happening here...i also checked via steam for errors, found some, downloaded those files, restartet KSP but it didn´t work......

[Yuki]

Picture of your craft would help.
To give it a shot: Do you have enough electricity? You mentioned THREE SAS systems and a quite heavy craft, those need quite some electricity.

[Fajita Jim]

Did you rotate the principle craft? AKA is your navball pointing up?

[rafalsli]

Actually I have the same problem with all my crafts (space, plane). They're just not stable. After a minute into the flight they cannot keep a heading. SAS or not they start spinning around. At this point game is unplayable, because it takes both costant corrections and luck to get anything into orbit. Any constructive help would be appreciated.

[Viper31st]

Originally posted by Yuki:

Picture of your craft would help.
To give it a shot: Do you have enough electricity? You mentioned THREE SAS systems and a quite heavy craft, those need quite some electricity.

is 20 000 units of electricity enough?
guys believe me, i have turned on SAS, there is a ton of electricity, got enough fuel, nav-ball is pointin up, i play this game for a long time now, 2-4 years, i guess, don´t think i am a beginner, but you don´t know that....anyway....the problem seem to be fixed by de-installing the game and re-install it. save games would not be harmed by that step.

[Viper31st]

An update:

since i re-installed KSP, i managed to do some pretty nice flights, with my ships (of course SAS turned on and got enough electricity)...but suddenly......again, this riidiculous thing happen....SAS failure.....during lift-off phase....safed the ship, brought it into an orbit, saved the game, ended KSP, restartet it, reloaded the game, and still SAS goes crazy....

for the info, i have no mods installed, only the game, no dlc´s added......checked the game via steam for errors....nothing.....
slowly i am very frustrated and slipping into "rage-mode"....slowly....

[desrtfox071]

So, I've never had SAS demonstrate a "bug". I've seen unflyable ships due to balance/lift. I've seen SAS stop due to electricity, antenna connection, etc. I've seen SAS behave "weird" due to me using a misaligned command pod, for example.

I second the "please attach a pic of the ship" for any of these sort of issues.

[Viper31st]

ok....the ship-thing...believe me, there is nothing "misaligned, and yes, i can post a picture of it, but there is nothing wrong with the design, believe me....do yourself a favour, read what i have written, the thing is...sometimes it happens, that the ship turn over the point, that i have selected by SAS (prograde, retrograde, etc. ). For example: i turn on SAS, give full throttle (at launch-pad), and then i ignite the engines. SAS should help you, to keep your "ship" under control, but yes, i switched it on, but it does not have any effect, it is like, i never switched it on....that is what it feels like. next thing...in space, if i want to point my ship from pro-grade to retrograde, i press the button, given me by the SAS and then the ship starts spinning into the direction, it should, but it will not stop, it will spin in the same direction, again and again, and everytime, it spins faster and faster.
after, ending KSP-session, by quitting the game, restart it, end it again, cause the problem still exists, restarting my pc (my pc is ok, for those, who maybe think, it is all about my pc!), restarting KSP again....and suddenly it works....

Originally posted by desrtfox071:

So, I've never had SAS demonstrate a "bug". I've seen unflyable ships due to balance/lift. I've seen SAS stop due to electricity, antenna connection, etc. I've seen SAS behave "weird" due to me using a misaligned command pod, for example.
.

note: it is not really smart to think, only because you never had experienced such problems, that they don´t exist...(not offensive...)

[Viper31st]

what sort of screenshot, did you wanna have? inflight? hangar?

[Viper31st]

https://steamcommunity.com/sharedfiles/filedetails/?id=1805099860

https://steamcommunity.com/sharedfiles/filedetails/?id=1805099806

https://steamcommunity.com/sharedfiles/filedetails/?id=1805099806

from hangar

[desrtfox071]

Originally posted by Viper31st:

ok....the ship-thing...believe me, there is nothing "misaligned, and yes, i can post a picture of it, but there is nothing wrong with the design, believe me....do yourself a favour, read what i have written, the thing is...sometimes it happens, that the ship turn over the point, that i have selected by SAS (prograde, retrograde, etc. ). For example: i turn on SAS, give full throttle (at launch-pad), and then i ignite the engines. SAS should help you, to keep your "ship" under control, but yes, i switched it on, but it does not have any effect, it is like, i never switched it on....that is what it feels like. next thing...in space, if i want to point my ship from pro-grade to retrograde, i press the button, given me by the SAS and then the ship starts spinning into the direction, it should, but it will not stop, it will spin in the same direction, again and again, and everytime, it spins faster and faster.
after, ending KSP-session, by quitting the game, restart it, end it again, cause the problem still exists, restarting my pc (my pc is ok, for those, who maybe think, it is all about my pc!), restarting KSP again....and suddenly it works....

Originally posted by desrtfox071:

So, I've never had SAS demonstrate a "bug". I've seen unflyable ships due to balance/lift. I've seen SAS stop due to electricity, antenna connection, etc. I've seen SAS behave "weird" due to me using a misaligned command pod, for example.
.

note: it is not really smart to think, only because you never had experienced such problems, that they don´t exist...(not offensive...)

Ok, so i looked at your shots. Let me say a couple of things first. I never said that my experiences are universal. I do however have quite a few hours spent in the game and have experienced a lot of things, and can say that maybe you are overestimating your own position.

Looking at the pictures, I'd say there certainly is a lot of room for problems with that ship. Let's start with the basics - fuel drain. Given that you have fuel tanks outboard of your main "stack" any non-isotropic drain of fuel could cause that ship to behave terribly. Second, the same is true for the outboard engines, especially if they are allowed to gimbal, and even moreso if those outboard side boosters flex at all under load.

I'll also say that the vessel in the pictures is probably going to have major issues in any atmosphere at speed, so based on your description of the issue, I'd say you're getting aerodynamic effects once you get up to speed, that is causing the drag to be at the very front of your rocket, vs the back where you want it, which is inducing the craft to wander, then flip over. Also, it probably flexes a bit in between causing horrible oscillation. Probably no amount of SAS is going to be able to make that stable because the aerodynamic forces will want to make that ship fly backwards, and the faster you go, the moreso. SAS will probably hold it for a while, as long as it doesn't get very far off prograde, but as soon as it does, it won't be coming back because the SAS won't be able to torque it around in order to fly in the opposite direction of what is aerodynamically stable for that vessel.

The fix for this would be to make sure that the booster part of this vessel has an extremely large drag in back. This probably can't be achieved with this design though, so you'll have to either go really, really slow through the atmosphere or completely redesign the ship. One thing that might help is adding a long section to the back of the middle core and giving it some "fins". This could help it have the necessary lift/drag vs CG positioning.

In space the drag vs CG thing shouldn't matter, but all the asymmetry/flex issues will still matter, and you may also have excessive thrust on it while in space, exacerbating the issues. So, while in space, restrict the engines to something like 10% thrust will probably help.

[Buflak]

Could you share your .craft file?

[Viper31st]

ok again...it has nothing to do with the ship/rocket itself...maybe there is room for improvement, but it works, i used it many times, WITHOUT any issue, you looking at the wrong point, if you think, that it has to do, with drag, or booster-parts, or engine-gimble. the moment, when the problem showed up, was up in space, no thrust, only maneuver, by clicking on the SAS icons, and the part, with the lift-off, yes, it felt like SAS was NOT enabled. but it was...

no critics to your critics, about how i built my ship, but again, it worked many times, there is nothing wrong with it, in my opinion.

[Viper31st]

Originally posted by rafalsli:

Actually I have the same problem with all my crafts (space, plane). They're just not stable. After a minute into the flight they cannot keep a heading. SAS or not they start spinning around. At this point game is unplayable, because it takes both costant corrections and luck to get anything into orbit. Any constructive help would be appreciated.

again....this is, what i am talking about