Avoid my rocket from spinning?

[brusura]

Hello,

I have modified my launcher with the remote guidance unit instead of the 3 man command pod, but now it start spinning because the torque is not enough I think, but why the spinning at all?

Here is the craft file ( stock ): https://www.dropbox.com/s/so25q5bsb7s1fm0/Lewis%20%26%20Clark%20-%20Station%20Core.craft

the spinning start to be uncontrollable after the first stage

edit: clustering engine is bad for rotation anyway, symmetric or not, this version without the clustering do not rotate like crazy https://www.dropbox.com/s/9pejy5mmptjvnno/Lewis%20%26%20Clark%20-%20test.craft

Edited July 21, 2013 by brusura

[brusura]

Uhm...actually I think to have found the reason just now, because I am using a 3 engines configuration and the mirroring thing put the engines in the opposite direction...

Uhm...answered myself sorry

[brusura]

Well...it went way better until out of atmosphere then it starts a little rotation and when hit last stage again uncontrollable rotation, but the cluster in the last stage is symmetric uhm...

[dave4002000]

You had the right idea with the fuel lines for an asparagus staging system. But your actual stages and their order are all messed up. What i imagine, is that you were decoupling everything below the nuclear engine before the main central stack was finished burning. So you had this huge rocket pushing you from behind, but since you decoupled it, you had no control over it at all.

Try this setup. Everything is exactly the same, i just fixed your staging problems. You should hit the spacebar when the first 2 booster stacks burn out, then hit it again when the second 2 booster stacks burn out. That will leave you with the main central stack still burning and under control. After the staging fix, i had no problems with stability and it flew dead straight all the way to orbit.

::edited link:: I gave the raw format the first time.

https://www.dropbox.com/s/62x51hudakoc9va/Lewis%20%26%20Clark%20-%20Station%20Core%20Fix.craft

Edited July 21, 2013 by dave4002000

[brusura]

Hi dave,

I missed the last decoupler yeah, but that unfortunatly do not change things a bit, the last stage seems to be the problem, the first two first stages overcome the rotation force from the central one, when the first stage is gone I start to see a little compensation from ASAS on the roll axis, then when the second stage is gone the ASAS full compensate on the roll axis, if I turn ASAS off in the last stage it's just spinning without control on the roll axis, if I turn engines off or throttle down and ASAS back on the rocket stabilze, so it's something with le cluster configuration on the last stage.

I dunno how you could flight it straight all the way to orbit without noticing this uhm, maybe it's the way am I flying it? I have ASAS always on and hit F to do the course correction

Edited July 21, 2013 by brusura

[dave4002000]

Well, i let mechjeb fly it before when i was testing and it had no issues, at all. After reading your comment, i just flew the entire launch manually(mechjeb wasn't even installed) and i still didn't have any issues. It did want to roll a little bit, but nothing that i couldn't control by using the 'Q' and 'E' keys. How are you flying your ascent? When do you start your gravity turn?

[brusura]

I have uploaded a video to better explain it, the last stage just keep spinning, if you see, in the video I used the rcs to kill momentum and then let the rocket free without using asas or rcs, it just start spinning again °_°

During the whole flight when I disable asas with F it always want to roll

ps: I have no mods on this installation

[Cheebsta]

Every time I use fins on my rockets that happens. I thought maybe it was because the fins have lift, and are all applying that force in the same direction, since they don't realize this is actually a rocket and not a plane. This is a completely off the top of my head guess though.

[MrTaxman]

I think Cheebsta is correct. I find I have the same problem (spinning) when I use fins on my final stages. I figure it trades atmospheric maneuverability for rock-steady directionality in LKO. *shrug* I figure it's a small problem for a large benefit.

[ASnogarD]

I get the same issues all the time, cant work out what it is... often the usual advice is put on 'moar struts' .

Wanted to make a basic lifter, center stack (engine + duel = stack ) and 6 radially mounted stacks in asparagus staging ... that's it, each tank is strutted, each engine is strutted , the radial mounts have struts to strengthen the connection between center and outer stacks... all symmetrical and balanced, yet the craft spins.

By the time the bugger is in orbit its spinning like crazy and totally ignore Q and E inputs (expected though as it only has ASAS and a Probe).

Done all the usual tricks, disabled gimbals on the outer engines, tried strutting the stacks together, then only to the center, no struts at all (between stacks), cross strutting, checking no strut is in contact with another...

I gave up and added AV-R8 winglets which controlled the spin while in the atmosphere and until I went to do my gravity turn... the second I touched F (Disables SAS if you hold F down) the craft jumped at the opportunity to enter the spinning top competition (and damn it is a good contender for that competition).

It annoys me no end as there isnt a logical reason why, if I had a extra part on the side I could get that... balance was off, or if it wasn't symmetrical I could get that too, but there isnt a logical reason ... just a vague notion I need 'moar struts' ...

... so I gave up until the update, no point in getting more annoyed with the work in progress software until I check out the updates, for all I know the ASAS / SAS / Rotation Rings / Whatever will sort out most the crap I am having with spinning so all the swearing and calling the game everything under the sun will be for naught.

[Cheebsta]

The thing you need to watch with "MOAR STRUTS" is that if you are putting on struts that are not parallel to the rocket up and down, drag on those angles is going to induce a spin if you don't put another strut at an opposing angle to balance it out. Fuel lines also cause this. It typically happens once you stage and struts start to vanish.

[dave4002000]

Ok, i played around with this a little more. It's not the engine cluster that's giving you issues. Because i replaced all those engines with 5 mainsails and the roll problem increased tremendously. What i noticed though, was that you didn't use 4-way symmetry to mount your radial boosters. I know this because i couldn't use 4-way symmetry to mount the mainsails. I had to use 2-way symmetry, twice. I would advise you to start from scratch and use 4-way symmetry on your boosters. With all those random cubic's and struts everywhere, the game probably didn't line up something correctly with the divided symmetry and that's what is causing your roll issue.

[brusura]

Actually I have removed the clustering and used 4 skipper and 1 mainsail and the rolling was gone, anyway I am going to try out the cluster with 4-way symmetry also I am going to do another test without the fins/winglets ( without touching the symmetry ) and see the outcome.

Thanks all for the answers

[dave4002000]

Actually I have removed the clustering and used 4 skipper and 1 mainsail and the rolling was gone

Haha, alright then. I have no idea why our experiences of the same craft differ so much. But as long as you figured it out, that's all that matters