CoM and CoT

[Khalani]

So How should I design my rockets so they don't flip over during launch?
I searched for some tutorials and some say CoM at the bottom, CoT near it.
At the moment my bigger rockets tend to flip over all the time :/

[Chibbity]

A proper rocket is like an arrow.

Mass at the tip, long sturdy shaft, feathers at the bottom.

So actually you want COM high, and COL low. Obviously COT should always be at the very bottom, In the same way that a bow string sends the arrow flying from behind. Add lot's of fins/aero surfaces to the rear of your rocket to help stability in flight.

[Khalani]

Alright, thanks. I'll try to crash a bit less ;)

[Chibbity]

Originally posted by DaFG Khalani:

Alright, thanks. I'll try to crash a bit less ;)

No problem.

Also, going too fast too early can cause flipping in some cases. So try not to be launching off at insane TWR's.

Reaction wheels never hurt either. Even if you just add them to an early stage you'll discard, they aren't that expensive.

[RoofCat]

you can also have "front wheel drive" rockets - with CoT high up. Very stable solution. In fact may be a bit too stable for a gravity turn, but I haven't encountered many problems so far since some of the engines will stay at bottom anyway. Because there is free spot, right?
Just attach some boosters higher up. It won't be great for the decoupling safety, but is perfectly doable. Decoupling may be solved with spinning - centrifugal forces.

Flipping happens mostlly due to either flat nose or light payload. Low density to be more accurate - large in size (high drag and distance from the main mass) yet light. Design them intelligent.


no screenshots in 2017...

[Jim Harlock - Pirate]

I tend to make my rockets Skinny and tall. Make sure your payload isn 't much bigger around than your rocket. Also, Something that helps me is to adjust the thrust of your first stage engines. Make your initial TWR just above 1...like 1.1 or so. That way, your rocket starts off slow and picks up speed as it burns fuel. I start my gravity turn at about 3-4 km up and slowly turn the rocket over. Helps my quite a bit.

[Chris99673]

The reason why your rocket might tilt while launching might be because the COT isn't on the same vertical axis as the COM. That's very important... but you don't have to worry about that if you build your ship symmetrical.

[[insert_name_here]]

The thing is, if your COM is too high, your rocket becomes really top-heavy and it's very difficult to do a gravity turn low in the atmosphere, so I prefer a lower COM. But the COL should always be as low as possible.