Why are my orbits always weird?

[Ruskiwaffle1991]

It's a huge problem especially when going to the Mun. Most of the time my rockets seem to be aerodynamically stable but once I pitch downwards to yaw sideways they sometimes roll. 

[CyberDroog]

Have you tried letting K2-D2 fly it? I use K2-D2 for serious flights anyway.  (K2-D2 does some of what MechJeb did for KSP1) But even still, you might get an idea of what's happening at least. If K2-D2 can't control it, then perhaps there is(are) a design flaw(s).

[king of nowhere]

6 hours ago, Ruskiwaffle1991 said:

It's a huge problem especially when going to the Mun. Most of the time my rockets seem to be aerodynamically stable but once I pitch downwards to yaw sideways they sometimes roll. 

first of all, the thread title does not match the question. orbits refers to moving in space, ascent would be more appropriate for atmosphere. it seems your rocket has stability problems.

unfortunately, you do not give us enough information. pictures would be good. maybe your rocket isn't as aerodinamically stable as you think. or maybe you are turning it too hard.

why would it be a problem especially for going to mun? how is that rocket different from others? this may shed light on the problem

[Aelfhe1m]

1. Adding fins to the rear of small rockets can improve aerodynamic stability during early parts of flight. This may not be needed if you have engines with a high degree of gimbling instead. Most but not all rocket engines in KSP have quite large amounts of gimbling (this is shown in the right hand side of the part menu in the VAB)

2. In the VAB turn on the Centre of Mass (CoM) and Centre of Lift (CoL) indicators (buttons near bottom left of screen) and check to see that the blue ball (CoL) is lower than the yellow ball (CoM). If you want to be extra thorough check to see if this changes if you empty the fuel tanks.

Having the CoL above the CoM will cause the nose of the rocket to be more prone to moving off course if you deviate even slightly from prograde. Conversely, having the CoL far below the CoM may make turning slightly sluggish and the rocket more "determined" to stay pointing in the direction its currently travelling.

3. During early parts of flight, it is generally a good idea not to turn too far away from your prograde vector. A good rule of thumb is to keep your direction indicator inside the prograde vector circle on the navball. Tap controls when turning rather than holding them down and use fine control (caps lock on keyboard) if necessary.

4. Start turning early and smoothly rather than trying to make larger corrections later in flight. This will vary depending on the exact design of your rocket (mostly based on the TWR of your stages), but a general rule of thumb is to fly vertical until you reach about 80-100m/s speed then pitch over 5-10° and then keep pitching over gradually until you reach about 45° at around 25 km altitude and be pointing more or less horizontal by 50km. 

NOTE: these figures refer to stock Kerbin atmosphere if you have any mods that replace Kerbin or change the atmosphere, then you may need to adjust for those.

5. Don't worry too much about getting to a perfectly equatorial orbit for going to the Mun. An small orbital inclination can be corrected quite easily (and for little cost in fuel) during transfer.

[RunaDacino]

1. Adding fins to the rear of small rockets can improve aerodynamic stability during early parts of flight. This may not be needed if you have engines with a high degree of gimbling instead. Most but not all rocket engines in KSP have quite large amounts of gimbling (this is shown in the right hand side of the part menu in the VAB)

 

Adding to this, although modded - I found taller/longer rockets to fly much, much nicer than short and stocky ones. Using cryogenic engines, you build very tall for the same deltaV/mass and they... you let go of SAS and naturally do a gravity turn and it's beautiful. 

 

Is there a way you could make your rocket taller without making it heavier?

 

2. On the flipside, payload.

Make sure your payload is not much more wider than the rocket underneath it. A super wide fairing will introduce more lift than the fins at the rear and make you flip out like crazy. If you can keep your fairings relatively straight, you're good. Slightly flared out (with symmetry on bottom and top ideally) also works but... don't make it too wide. This too wide is sth I ran into a lot during my early lander designs and struggled horribly because of it. 

 

Something that can help you there is knowing you can attach fairings to rocket parts. Like, rockomax tank, 2.5m fairing, science junior/random junk, heat shield and pod. You attach the fairing to the pod's bottom rather than cover it as well.