Flight Question Stock DG unstable in orbit

[mike_espo]

Using a few of the stock scenarios for the DG, I find that while in a circular orbit of roughly 300km, ecc~.002 that the DG tumbles a lot! I would think that it would be fairly rock stable at 300km.

Is this a bug or am I missing something?

thanks

 

[ar81]

If you have non spherical gravity enabled, blame sun and moon for changing your orbit. If disabled, blame orbit eccentricity for changes in altitude.

 

[mike_espo]

Its not so much altitude, but attitude that is changing, even if I enable level horizon, thrusters fire constantly to maintain attitude.

 

[garyw]

They will. Try letting the ship settle into a prograde orbit first. That will reduce the thruster firings or just hit numpad 5 (killrot) that should do the same.

 

[Brassbud]

I'm a little confused by your last post. Your attitude with respect to the horizon should and will change over time unless the period of your rotation matches exactly the period of your orbit (a feat nearly accomplished by the Moon).

Now, even if this is the case, the gravity gradient torque will cause your ship to oscillate as well, unless you are flying a spherical ship or are already in the most ideal orientation.

 

[unknown_orbiter]

Hey simple answer: Get into your orbit, burn prograde all the way, then turn it off. Yur ship will have enough rotational momentum to keep it pseudo-prograde for quite some time. When you drift too far, re-prograde and repeat. Time-warping while in an autopilot (prograde, antinormal, auto-level etc) will cause wobbling and violent shaking.

 

[mike_espo]

Thanks guys. It seems to do better when ship is in prograde attitude.

 

[tblaxland]

I suspect you have gravity gradient torque enabled. There was a more detailed discussion of its effects recently in this thread:
http://orbiter-forum.com/showthread.php?t=4850&highlight=gravity+gradient

 

[SlyCoopersButt]

What Unknown_Orbiter said was exactly what I do when I need to use Ion engines in Earth orbit. I need to run such engines months at a time in roughly prograde direction using that method as hydrazine could never last.

 

[ar81]

Also if you have turned your hover engines on you may wonder why ship behaves in undesired manners.

 

[tblaxland]

Also if you have turned your hover engines on you may wonder why ship behaves in undesired manners.

Yes, always check that your 4yo son has not been playing with the throttle sliders before starting the simulator session...

 

[Fixerger]

Try pressing * key. If not help, check out your quicksave for THlevel line.

 

[Brycesv1]

if ur orbiting around the earth then ul always be facing the same direction even when the earth is in a different relative location. it makes kind of an optical illusion where u think your rotating but its just the earth going around you. rotate at the same speed that your going around the earth and ul stay level with the horizon