Long Fairing Makes Rocket Flip-Prone

[SievertChaser]

Yeah, it's that kind of thread. I have a ship riding a small hydrogen-oxygen stage with a thin-skinned tank; because the two use 1.25 m engines, I just covered everything in a long fairing.

And the stack ended up ludicrously flip-prone when flown by MJ; even a slight turn sends them tumbling. I've created extra drag by using a 3.75 m first stage with eight fins, and it still ended up flipping.

Anyone ever fought the issue?

[Manwith Noname]

There was an issue with fairings in older versions whereby the drag force was being applied waaaaaaaaaay ahead of the fairing nose, so the torque generated was much larger than it should be.

I thought this had been fixed but it's possible it could still be lurking in some way I guess.

[Washell]

Originally posted by Manwith Noname:

I thought this had been fixed but it's possible it could still be lurking in some way I guess.

Easy enough to check by hitting F12 and see whether the drag arrow is properly inside the fairing or way ahead of it.

@Dennis: Picture of the rocket in question?

[Stickmiin]

you can also counter that with some tail fins, they arent the prettiest but they work :p

[Kenonan]

Maybe take at least part of the fairing off? If you dont go more than 300 m/s for the first ~15km you should be totally fine. Unless you are shipping a rover or something like that, I've never had a huge use for fairings.

[SievertChaser]

Originally posted by Kenonan:

Maybe take at least part of the fairing off? If you dont go more than 300 m/s for the first ~15km you should be totally fine. Unless you are shipping a rover or something like that, I've never had a huge use for fairings.

I had not one but two 1.25 m sections under there. So I'd get even more drag.

Originally posted by Stickmiin:

you can also counter that with some tail fins, they arent the prettiest but they work :p

Had eight of them, no effect.

Originally posted by Washell:

Originally posted by Manwith Noname:

I thought this had been fixed but it's possible it could still be lurking in some way I guess.

Easy enough to check by hitting F12 and see whether the drag arrow is properly inside the fairing or way ahead of it.

I've seen reports that the F12 overlay ignores the existence of cargo bays.

Right now it seems to be an MJ problem rather than an aero problem.

[King_BR0K]

yes mj needs a very stable rocket
try limiting aoe to 3

[SievertChaser]

I did try. Didn't really help.

The current release build appears to be sensitive to oversteeeing. The dev build has proven slightly handier, but overall I managed to get a rocket flying (see my recent showoff thread and screenshots) by grossly violating the basic instructions of ensuring rocket stability and removing all fins.

[Rhedd]

Originally posted by dennis.danilov:

I did try. Didn't really help.

The current release build appears to be sensitive to oversteeeing. The dev build has proven slightly handier, but overall I managed to get a rocket flying (see my recent showoff thread and screenshots) by grossly violating the basic instructions of ensuring rocket stability and removing all fins.

Fins are totally unnecessary 99% of the time. Notice how many real rockets have fins? I very rarely put a fin on anything. I'm sure anyone who reads my posts gets tired of hearing me say it, but my rockets never flip.

What's the ground thrust-to-weight ratio on this ship that always flips?

PS: One tip if MJ keeps flipping your rocket is to turn Corrective Steering OFF. Limit the AoA, but turn that steering off and leave it that way.

[SievertChaser]

Originally posted by Rhedd:

Originally posted by dennis.danilov:

I did try. Didn't really help.

The current release build appears to be sensitive to oversteeeing. The dev build has proven slightly handier, but overall I managed to get a rocket flying (see my recent showoff thread and screenshots) by grossly violating the basic instructions of ensuring rocket stability and removing all fins.

Fins are totally unnecessary 99% of the time. Notice how many real rockets have fins? I very rarely put a fin on anything. I'm sure anyone who reads my posts gets tired of hearing me say it, but my rockets never flip.

What's the ground thrust-to-weight ratio on this ship that always flips?

PS: One tip if MJ keeps flipping your rocket is to turn Corrective Steering OFF. Limit the AoA, but turn that steering off and leave it that way.

1.6-to-1.8; 2+ gets me flipping. I'm slowly getting there, but in ye olden 1.0.5 fin spam was quite adequate.

I'm using AoA set to 5, what's your suggestion?

Yeah, I'm definitely no longer attached to fins. Especially when I need to get into space fast.
http://steamcommunity.com/sharedfiles/filedetails/?id=691625184
http://steamcommunity.com/sharedfiles/filedetails/?id=691625639
http://steamcommunity.com/sharedfiles/filedetails/?id=691625754

[Rhedd]

AoA should be fine at 5.

I know it sounds crazy, but seriously try launching with a TWR of around 1.3. I actually like to aim for about 1.25 or so. Frankly, I'd consider anything over 1.5 to be excessive. These figures are based on real-life rockets, and they work great.

There might be a bug with really long farings, but I haven't run into it. I've launched extremely large sections of a munbase built out of Planetary Base Systems parts, covered in quite long farings, and not noticed a problem.

Set your MJ ascent path to a 60% turn shape, get your TWR in the 1.3 range, and give it a try. See how it goes.

Also, if your rocket flips at high altitudes or you see flames on the way up, try turning an engine off (assuming your rocket has more than one and it can be balanced) at about 20-30km to keep from exceeding maxQ and flipping.

Watch your time to apoapsis. If it exceeds a couple of minutes, your thrust is excessive. (Although it can be hard to keep it that low.)