Patch 1.02, Spinning to space

[Flynotsohigh]

Yesterday, during playing some KSP, and enyoing my first orbital flight, suddenly I've been kicked out. First I was like "Thanks Obama", but then I realised it was a patch. Today I'm trying KSP again, wanted to do some mission, but every rocket I build so far is very unstable, spinning even at lower speeds like 100m/s. Impossible to takeoff and killing the fun (Tried with SAS and without, doesn't matter). Do I have to do a practicum at ESA to play this game now? Since 1.02 I can't start a single rocket because every rocket (which actually have worked perfectly before the patch) is spinning like hell in lower atmosphere. Am I doing something wrong? I started a lot of rockets before patch and didn't have any problems at all, but now I am just wainting for help or another patch because that is not working in any way.

[diomedea]

Yes, a crash course at ESA, NASA, or any aeronautics school would help.

KSP 1.0 implements credible aerodynamics now. That means, when moving in dense atmosphere, the aerodynamic forces are fierce enough to make a craft spin until its Center of Pressure is downstream in respect to the Center of Mass. The trick is to build crafts that already have the Center of Mass forward of the Center of Pressure (or, use the Center of Lift in the editor, as KSP does not show the Center of Pressure). That makes crafts stable in flight.

[katateochi]

it isn't "needs MOAR boosters anymore", it's "needs MOAR fins". I have found that a quick fix for some of my rockets is just to slap a bunch of fins around the bottom and if you switch the aero-forces display on (f12) you can really see what they do in preventing the bottom of the rocket from rotating. I've also found you need a lighter touch when going into the gravity turn and again turning on the aero-forces display does help show what's going wrong if you do start to spin.

I'm a little miffed that it seems that all rockets need fins now. I've been trying to recreate Dragon lander and Falcon9 LV (and have the first stage so it can be landed). Falcon9 doesn't have fins, but in KSP it really needs them, so.....I turned them around and stuffed them inside the lower tank. It works and has the aesthetic look that I'm after, it just might enrage the "no part clipping" crowd.

[mikegarrison]

Yes, a crash course at ESA, NASA, or any aeronautics school would help.

KSP 1.0 implements credible aerodynamics now. That means, when moving in dense atmosphere, the aerodynamic forces are fierce enough to make a craft spin until its Center of Pressure is downstream in respect to the Center of Mass. The trick is to build crafts that already have the Center of Mass forward of the Center of Pressure (or, use the Center of Lift in the editor, as KSP does not show the Center of Pressure). That makes crafts stable in flight.

It has been an odd week.

On Saturday, I was launching rockets using MechJeb, going straight up to around 6000m, then going hard over and flying automated SAS all the way to orbit. No fins. No shakiness. 4400 m/s to get to orbit. Any stupid shape I wanted.

On Monday and Tuesday I was learning to build smaller rockets, kick them over slightly right off the launchpad, just play with the thrust and let them turn themselves, no SAS. About 3000 m/s to get to orbit. Fins were necessary. No aero forces after about 25000 m. Re-entry could be avoided just by staging chutes in space. I decided to try playing totally stock, just to see how it would work.

After the patches, now that gravity turn isn't working for me anymore. The rockets just wobble around randomly. But SAS causes them to go all wonky, so that's not an option either. I've been having to steer them by hand and not let them just fly themselves. I've had to go much more straight up. Aero forces still pretty strong into the 40000 m heights. Good thing that I tried to learn the new re-entry before, because now reports are the chutes burn up if you pop them while you are going too fast.

Anyway, it seems like every time I log in, the game physics work differently.

[Temeter]

Use the aerodynamic overlay, F12. Blue arrow means lift, and if, for some reasons, the upper part of your rocket creates (body) lift during flight, then your rocket will spin out fast.

One way to deal with it is to lower the center of lift during flight, notably by putting fins on the end of a rocket.

Edited May 2, 2015 by Temeter

[GluttonyReaper]

I'm a little miffed that it seems that all rockets need fins now. I've been trying to recreate Dragon lander and Falcon9 LV (and have the first stage so it can be landed). Falcon9 doesn't have fins, but in KSP it really needs them, so.....I turned them around and stuffed them inside the lower tank. It works and has the aesthetic look that I'm after, it just might enrage the "no part clipping" crowd.

I suspect that might have something to do with the low gimballing on the engines in KSP. Most modern rockets have much larger amounts of freedom with gimballing, which lets you do things like launch rockets with a single SRB strapped to the side and still keep stable.

[Majorjim!]

Use the aerodynamic overlay, F12. Blue arrow means lift, and if, for some reasons, the upper part of your rocket creates (body) lift during flight, then your rocket will spin out fast.

One way to deal with it is to lower the center of lift during flight, notably by putting fins on the end of a rocket.

The OP is talking about rockets spinning like a bullet not tipping over. I have experienced this too. I simply turned the rocket on the pad and let it naturally turn. And no more starting a turn at 1000m!

[AaronLS]

I'm experiencing tumbling on my rockets that were fine before as well.

I have a suspicion of why this is.

Is the resistance from drag modeled per part? Before all of the items in a stack generated drag, but now only the top item generates drag since the items behind it in the stack no longer create drag. Thus this would cause your rocket to act as if you threw a dart backwards.

If only the top of the stack is experiencing drag, such that there is a disproportional amount of drag on the top of the rocket.

Even if I put a fins on the bottom it doesn't help much unless I put alot, and that only helps the first stage. After that stage is ejected, the rocket then again tumbles. It seems like a ton of fins are required to create MORE drag than there is on the top, so that when the rocket is askew of prograde there is more drag on the bottom to bring it back lined up with prograde.

When the rocket is slightly askew of prograde in a thick atmosphere, the top item of the the stack generates drag, and the rest of the stack having no drag means that top item wants to flip to the back.