How to prevent uncontrollable tipping during ascent

[Stealth2668]

When I'm ascending, sometimes I will do my gravity turn and when I'm at the right angle I can't stop tipping. I know it's some sort of design flaw but IDK what it is. Should I have winglets (the controllable ones) above my CoM or below it on my rocket for the best control while turning?

Edited September 2, 2014 by Stealth2668

[Kryxal]

If you're using winglets, they go at the BASE of the rocket, though it's reasonable to put a second, smaller set on for second-stage control (depending where you expect to be staging, of course).

It might help if we could see the rocket, and it would also help to know mods in use and the engines you're making use of. I'm tempted to suggest more reaction wheels, but if you're using BTSM (for instance), that tends to not be the best idea...

[ratchet freak]

does your engine has gimballing? just the pod's torque is probably not enough

[Murph]

If you're doing a single huge turn, you might want to try doing a real gravity turn (vertical until 10km, then horizontal is not the way it should be done…). Pitch over gradually using small control inputs, starting somewhere around 5-10km (assuming stock aero), keeping your heading within 5-10º of prograde at all times, with the aim of being horizontal by 50km or when your apoapsis has reached the desired altitude.

MechJeb can be used as a good teaching aid, to show you how to do a steady, progressive gravity turn.

If you're using NEAR or FAR, adding tail fins and/or control surfaces may well be what's needed (as well as a proper gravity turn).

[Kasuha]

There are multiple possible reasons why your rocket may tip so a screenshot would definitely help.

Most likely reason is lack of control authority (reaction wheels or control surfaces) and unbalanced drag (symptoms suggest low drag part at the top, which is usually the command pod, or high drag part at the bottom which may be an SRB you're carrying along for some reason.

[Moonfrog]

tipping normally occurs in the most extreme sense with a tall heavy top payload. Your craft may not be an extremely tall with an extremely heavy payload, but that is why it happens. As you tip the lever force pulls it around. Solutions can involve more torque, which works in small tipping cases. Or you may have to redesign your rocket to be shorter and wider rather than thin and tall. Other option is to somehow cleverly get most of the heavy weight near the centre of mass so the top part is not the heaviest section.

I feel if u understand why it happens u be able to come up with a solution.

[nuclearping]

I'm also struggling with this problem. But I also think that this is just caused by my bad design building too "top heavy" rockets and wanting to bring as much payload as possible into space at once.

MechJeb helps alot for a smooth ascend, but also causes tipping if I don't "intervene" during the gravity turn. I found out that these things help:

1) Simply don't add too much payload.

2) Adding RCS Pods to the payload section helps avoiding tipping. But once it tipps over you still can't recover it tho.

3) Tipping mostly occurs until an altitude of ~20km and below a velocity of ~500-600 m/s. Above this the problem seems to smooth out.

4) When you're using MechJeb you can edit the "Ascend path", telling MJ when to start the GT and what Curve it should apply.

Edited September 1, 2014 by nuclearping

[Stealth2668]

If you're using winglets, they go at the BASE of the rocket, though it's reasonable to put a second, smaller set on for second-stage control (depending where you expect to be staging, of course).

It might help if we could see the rocket, and it would also help to know mods in use and the engines you're making use of. I'm tempted to suggest more reaction wheels, but if you're using BTSM (for instance), that tends to not be the best idea...

Ya, this was pretty much the issue. I moved them to the bottom then it was OK. I've since deleted the design though so I can't post pics. The tips however are still useful so thanks everyone

[Smorfty]

If your rocket is big (> 2.5 meter parts)

Put Vernor Engines at the bottom of your lifter.

Four of them: front, back, left, right. (I.E. not diagonally)

And remember to turn on RCS when you launch.

This way, they'll work like a lever.

I've launched rockets with +100 tons of payload with only four Vernor Engines and they've worked fine.

[Stealth2668]

If your rocket is big (> 2.5 meter parts)

Put Vernor Engines at the bottom of your lifter.

Four of them: front, back, left, right. (I.E. not diagonally)

And remember to turn on RCS when you launch.

This way, they'll work like a lever.

I've launched rockets with +100 tons of payload with only four Vernor Engines and they've worked fine.

Nice, I didn't even know those were in the game (haven't played in a while) Also, I'm playing career so I don't think I have those unlocked yet. I'm only about to unlock my first 160 science tech so IDK how far along those are.

[SRV Ron]

Swapping ends can be caused by a number of issues from certain parts in the payload section to broken struts on big rockets.

Examples;

This rocket with the cupola is unstable without fins while stable with the 3 man capsule.

This rocket swapped ends until a broken brace issue was fixed.

When fixed, it flew flawlessly.

[Thanny]

Vernors on the top with RCS active is definitely the way to go for top-heavy rockets. I got my fuel station into orbit in one piece that way, with 20 of the big Kerbodyne tanks (empty).