Solid Solution to the problem of need a new launch procedure

[SessoSaidSo]

Is there any solid means of preventing the flipping of the rocket besides attaching fins? I have tried active RCS assistance and still all I get is flips. I understand the problem very well, however, it seems that the only way to launch anything is to make it look like its from the 1950's. I am starting to just slowly launch straight up.

[spinomonkey]

I think the solution is either fins- or have enough punch from the liftoff that drag can't stop you. That being said... I've been forced to use fins thus far.

[Bill Phil]

How are you building your rockets>? If you build them right, they can steer on gimbal alone.

[Flayer]

I think it is also worth mentioning that the Reliant does not appear to have a Gimbal. I switched to the Swivel for increased control of my ascent.

[Alshain]

I've been able to launch without fins. But most rockets do have fins of some kind. Some use the protruding engine nacelles or even SRBs to double as fins. Really all you need is air pressure to be equal on both sides of an object to hold it steady.

Edited May 2, 2015 by Alshain

[NFUN]

I think it is also worth mentioning that the Reliant does not appear to have a Gimbal. I switched to the Swivel for increased control of my ascent.

Yeah, that used to be the main difference between them. In earlier versions they both had the same ISP, but the... Swivel traded some thrust for gimbal. Now that it has more ISP there isn't much reason to use the Reliant anymore, as it takes about no science to get the Swivel.

[LordFerret]

The Reliant engine lacking a gimbal can be part of the problem, it's a major annoyance for me anyway. Need for keeping a reign on your thrust and ascent velocity (and G's) is also an issue. Fins do help. I find sometimes that SAS can help (a little), but more often than not (for me) SAS just seems to fight with itself.

You should check out the boat-load of tips in GoSlash's thread here. I've asked for a Mod to sticky it, wish someone would.

[EtherDragon]

Ok first, start off by Reading This Tutorial. Seriously read it, love it, understand, then read it again.

Here is the main reasons your finless rocket flips over:

Center of Mass is near the tail.

Thus any Drag on the Nose has more Leverage than Drag on the (finless) tail.

Also, the greater your speed, the more air-resistance - hence more drag - hence more flippiness.

Here are the solid recommendations for those who are allergic to fins. Get an epee pin, and stop being alergic.

If that doesn't work, then do this instead - go slower. Speed = Drag = Torque = Flip.

If you must launch a rocket without fins, because it's "National Don't Use Fins Day" where you live, then you must follow this procedure:

Turn down your thrusters. Going too fast will kill you so don't.

Keep yourself nice and slow-ish about 350m/s until you are way up there (like 30km way up there)

On the way up, do your gravity turn very very gently. If your nose deviates more than about 5degrees from our flight-path you will flip.

And here's a big tip on speed - going slower at first, actually helps you have a more efficient gravity turn.

Your goal is to aim for 45degrees by 15km. So go slow enough to give your rocket time to arc over.

Once at 45 degrees and 15km and climbing you can throttle up. But make sure you keep your nose pointed strait at that Surface Mode Prograde Marker!

Launching a finless rocket on "National Don't Use Fins Day" requires precise control. Good luck!

(I prefer to call in sick on "National Don't Use Fins Day" and stay home until the next day, so I can use fins to keep my rockets stable.)

Also:

Edited May 2, 2015 by EtherDragon

[SessoSaidSo]

The point is, how many modern launch vehicles actually use fins? If the aero is supposed to me realistic, why do realistic launch vehicles not work?

[JWag]

The point is, how many modern launch vehicles actually use fins? If the aero is supposed to me realistic, why do realistic launch vehicles not work?

Real launch vehicles don't have fins because they have very good control algorithms that monitor angle of attack more precisely than you or I can. They are also flying ascent profiles that were exhaustively studied, modeled and simmed long before the rocket was ever assembled. Real launch vehicles are also flown in the same configuration over and over, building up a huge database of performance that feeds back into the algorithms.

When you and I throw something together in the VAB and toss a Kerbal on top and put it on the pad 15 minutes later, we haven't done any of that. I spend a couple of minutes doing "trade studies" in KER sometimes, but often I just fly the darn thing. We don't have a fancy guidance computer, or carefully calculated thrust profiles or anything. If SpaceX or ULA or Roscosmos or Arianespace did that, they'd be just as flip-happy.

EtherDragon's advice to keep initial velocity low is good. We have the luxury of extremely deep-throttling engines (an advantage none of the real rockets have).

I'm happy to see the new tiny fins. I've really been wishing for something like that.

Edited May 2, 2015 by JWag

[Jouni]

The easiest way to avoid flipping is to build bigger rockets. The bigger the rocket is, the less it cares about aerodynamics.

I've had some trouble with 1.25 m rockets, especially if the main engine is an LV-T30. 2.5 m rockets are much easier to fly.

[JWag]

I don't think the LV-T30 has ever had a gimbal. If you use one of those on a 1.25m rocket, you're only steering with the (wackily OP) reaction wheels.

We have another disadvantage when playing with a keyboard: It's very hard to make tiny adjustments to your trajectory in KSP. Unfortunately, when you're at max-Q the last thing you want to do is slew your control device to full lock.

Edited May 2, 2015 by JWag

[problemecium]

If it hasn't been covered, here's what I've discovered (copied from another thread where I posted it):

KSP 1.0.2 is very, very sensitive about where the center of mass is vs. the center of drag / aerodynamic pressure. You can't see where that is in the editor, but it seems to generally be roughly in the middle of the ship. Thus rockets that drain their fuel from the top are doomed unless they have some pretty powerful fins. But rockets that drain their fuel from the bottom have a much easier time of things, or in other words, you have to block fuel flow to the engines and then run a fuel duct to them from the top of the ship. It's hard to make ships this way that aren't ugly, but once I started getting the hang of it my launches immediately became significantly easier. So, uh, "pro tip" I guess.

[PuchForLife]

I just hit caps lock before launch to give me fine control it helps with woble to

[Jouni]

There's a simple technique for keeping the center of mass of a rocket high enough during the ascent. It's called "staging".