Inclined Orbit Unstable? Need More Information.

[Corax]

I think I need some information regarding inclined orbits. I currently have a mission in an inclined munar orbit, swinging back and forth between around ±30° of latitude. I\'m aiming for an altitude of around 3km ±200m. There is not much margin for error - some ridges rise close to 3km...

I haven\'t been able to keep the orbit stable for more than a few hours at best - several times now I have realigned apoapsis and periapsis to within some twenty meters. After a few orbits, they drift apart, I haven\'t been able to identify a pattern though. Sometimes AP appears to rise or fall; sometimes PE, other times both apsides change.

Now there are a few unknowns for me - I haven\'t been in such low an orbit for such a long time before (at least without going on rails), and most of my orbits so far were either equatorial or polar.

I was under the impression that as long as there is no atmospheric friction (and disregarding mass anomalies, solar wind, etc.), orbits would be stable no matter the inclination, but my understanding of orbit mechanics isn\'t firm enough to insist on it

[togfox]

Ill state the obvios before an expert comes.

Did you leave rcs or mechjeb on?

[Corax]

Ill state the obvios before an expert comes.

Did you leave rcs or mechjeb on?

No SAS or ASAS, no autopilot, and no RCS except for the reboosts. Simulation running at 1x time factor.

[r4m0n]

That is normal, physics simulation was quite a bit of error, so any orbit left running on 1X or 2X will be all over the place... If you go to 5X, the orbit will be set in stone and stay that way until you get back out of rails... Nothing you can do, really.

[Corax]

That is normal, physics simulation was quite a bit of error, so any orbit left running on 1X or 2X will be all over the place... If you go to 5X, the orbit will be set in stone and stay that way until you get back out of rails... Nothing you can do, really.

The only problem with that is you can\'t go on rails below 5km...

[Zephram Kerman]

apsides

I just learned a new word. +1 Internets for you! 8)

[Corax]

So, to reiterate, is it correct that:

From a physics standpoint, any orbit outside an atmosphere and above the maximum terrain elevation around any body should be stable, no matter the altitude or inclination; what would mess it up would be inaccuracies in the simulation?

Or, in other words: Theoretically I should be able to orbit the Mun just above the highest mountains, at any inclination, without the orbit being influenced from the outside in any way (Kerbin, the Mun itself, ...)?

My admittedly limited knowledge of orbital mechanics says it would work that way, but I\'m still not convinced I\'ve got all my facts and formulae right

[r4m0n]

So, to reiterate, is it correct that:

From a physics standpoint, any orbit outside an atmosphere and above the maximum terrain elevation around any body should be stable, no matter the altitude or inclination; what would mess it up would be inaccuracies in the simulation?

Or, in other words: Theoretically I should be able to orbit the Mun just above the highest mountains, at any inclination, without the orbit being influenced from the outside in any way (Kerbin, the Mun itself, ...)?

My admittedly limited knowledge of orbital mechanics says it would work that way, but I\'m still not convinced I\'ve got all my facts and formulae right

Within the game simulation limitations, that is correct. In the real world things are a bit more complicated, with uneven gravity fields and multiple gravity sources, so a orbit too low on the Moon would probably eventually crash somewhere.

But in the game, if you could switch to on-rails mode at 5km, you would keep orbiting forever.

[Corax]

Within the game simulation limitations, that is correct. In the real world things are a bit more complicated, with uneven gravity fields and multiple gravity sources, so a orbit too low on the Moon would probably eventually crash somewhere.

But in the game, if you could switch to on-rails mode at 5km, you would keep orbiting forever.

Ok, that\'s what I meant with influences from the Mun or Kerbin.

Thanks for clarifying, no more sleepless nights because of this