Flight Question Plane contantly changing

[Will]

Hello.

After getting into a stable orbit I tried to align orbital planes with MIR, this is nothing new and I have done it before. After the first burn at one of the nodes both my inclination and MIR's were constantly changing (at different rates) even though the rate of change still said 0 degrees per second. Also the orbit MFD said that both of our periapsis, apoapsis, altitude and eccentricity were also constantly changing. I had not installed any addons or changed any settings between that flight and the previous one.

Thanks for any help!

 

[Johnman]

I am no expert, but this happened to me when I had non-spherical gravity sources activated (among other settings regarding increased realism). Make sure you don't have anything like that active.

You can always delete Orbiter.cfg to reset all settings to default.

 

[Urwumpe]

That is normal behavior of real spacecraft, so don't worry about it too much. It is caused mostly by non-spherical gravity, a phenomena that you can disable. Then you only have the effects of sun and moon acting on your spacecraft, which also slowly change your orbit.

The change of your orbital parameters is another thing. Orbit MFD displays something called "osculating elements" in spaceflight, that are orbit elements that only approximate your real trajectory in your current position, the true orbit is the sum of many small segments of osculating elements. Such "approximating" elements have the advantage that they can be calculated in real time for display without expecting a small super-computer next to you.

You need to monitor your orbit elements for a few orbits to get more accurate information and filter out "periodic perturbations" (deviations from your average orbit, that are neutralized at the end of it) from your orbit. Or what is more practical, do critical orbit maneuvers in smaller steps, so you can correct the measurement errors before they grow too large.

 

[N_Molson]

The Moon and the Sun also change your orbit, depending of their relative positions to Earth.

 

[Grover]

in the paramaters tab of the launchpad there are two options that can cause this, nonspherical gravity sources and radiation pressure. both of these add a realistic uncertainty to the sim, like Urwumpe said, it happens to the real life spacecraft.

turn them off for this to stop, but leaving them on gives a realistic take of the sim, thats why its an option

-=Grover=-

 

[statickid]

Yeah I pretty much ignore those as they have no real consequence on the flight.

 

[n72.75]

IMFD's map program might be of some use. It can be set to show predicted orbital trajectory for a set amount of time.