Mikki`s guide of countering "Wobble" during ascend.

[Mikki]

Hi all, some of you may remember me, i am a seasoned KSP player and here is my advice to launch basically everything, even pancakes to orbit. 

Our goal is allways to perform a proper gravityturn, which ends up at between 70`001 meters circular or higher, depending on your missionprofile.

(Launching straight up is still a viable method of leaving Kerbin, nothing against this... )

Checklist on your rocket:

1. Thrust to weight ratio (TWR): A TWR of 1.4 or more and pulling full throttle all the way up trough the lower atmosphere will likely get you in trouble. In reallife rockets are throttled continously  to avoid exceeding pressurewaves along the fuselage (Max pressure limits at various speeds and shapes).

2. Drag: The use of cones and fairings is highly recommended, blunt surfaces will bend your contraption if you like it or not. Even large blunt tails  (i.e. Space Shuttle center tank) without rounded bottom increase drag alot.

3. Reaction wheels: More than one large active reaction wheel on a multistage craft will inevitably create trouble, having seven different reaction wheels all over the multistage rocket in different sizes, is likely to fail. Disable excessive reaction wheel authority during launch and you will be happier. 

4. RCS: We don`t need RCS during launch, never. Disable RCS. (Me at least ) 

5. Center of mass (CoM): Ideally, we want to have a launchvehicle which has and keeps  the CoM above the middle of the height of the rocket. But this is KSP, and we launch how and when we like to launch our pancake, i know. But designing your launchvehicle so that it stays topheavy is beneficial for your space program. Take a close look how soyuz and some proton rockets are buildt, the center stage is sometimes tappered wider on the upper half for this reason.

6. Max pressure: Maximum pressure occours at a certain height, speed and atmospheric condition, and is also depending on your individual launchprofile. Don`t slam your rocket into a wall.

7. Engine gimbal: Most of the available rocket motors for the first stage provide gimbaling by default. Reduce gimbal massively or disable gimbaling completely on asparagus style first stages on the outer engines, and your rocket will never be seen again on Kerbin...

8. Struts: Struts are meant to stiffen your core stage and connect boosters and the like with the core. You get the idea. Putting lots of struts to your craft can be necessary, but usually it takes just a minimum amount for the desired effect.

9. Control surfaces: Adding control surfaces and fins on strategic points on your rocket mostly helps, but avoid overengineering which often results in resonance to other means of control like reaction wheels.

10. Fairings: As far as i have seen fairings work fine in the current state of KSP2 (around EA 0.1.4 +), even giant ones do their job quite well. So i highly recommend the use of fairings, as intended by the devs.

11: Solid Boosters: Solid boosters (Aka ``The Poor Mans Launchpad``) are very usefull to save on methalox stages, its an issue of economy and designing concept to overcome the thick atmosphere on the cheap. I highly recommend the use of solid boosters to save on overall weight of the launchvehicle.

12. Gravity turn: Turning down your rocket gently towards the horizon while gaining altitude is a core challenge in KSP and KSP2, if your 1500 ton twelve stage interplanetary launchvehicle can do this with activated fine controls, you have won the game.

13. G-forces: We have a G-force indicator left to the Kerbal portraits, which is also very usefull to keep a sane amount of thrust while ascend, i don`t observe this feature often myself, but sometimes it is helpfull. 

 

One picture to think about:

Happy launchings!

I hope this little guide was somewhat usefull for one or the other (New) player... 

Edited October 14, 2023 by Mikki
you guess it typo, and spell, G-force

[Socraticat]

Gimbals and control surfaces should be adjusted to the minimum percentage necessary to function properly to reduce the "resonance" that you're talking about. Between that and isolating jobs for certain control surfaces, I can get some decent control over most launches.

Thanks for sharing your tips!

Edited October 10, 2023 by Socraticat