Flight Question Time warp uncontrolable rotation

[marcheenek]

Newbie to Orbiter. I'm practicing orbiting and deorbiting and reentry with DGIV and have an issue with the time warp. I'm aiming at Wideawake, which is 4th orbit after undocking from MIR. I set up AeroBrake and BaseSync and try to accelerate time to be on a final orbit, but every time I go 100x DG starts spinning uncontrollably, even if I have it on KillRot or Prograde. No such thing happens if I accelerate only to 10x. 100x causes ship to 'wobble' first then it goes into weirdest spins and rolls, which cannot be stopped. Is this a known bug or I'm doing something wrong?

 

[Nazban]

This is a known bug in Orbiter, The orbiter program cannot take more than 100x speed normally.

 

[RisingFury]

Autopilots are unstable at high time compression. My computer can generally handle up to 100x, but beyond that it just goes wonko. I tend to turn off all autopilots when dealing with high time compression. That includes the AeroBreake's hold AOA autopilot.

If all autopilots are off and your ship still starts to wobble around - though far slower - that's because of gravity gradient torque. I generally let the ship wobble around on orbit and only stabilize it once it's time to do the deorbit burn.

 

[orb]

Orbiter calculates elements every frame, so if you have enabled vertical sync. and monitor's refresh rate is 60 Hz, and you don't use "fixed time steps" feature, you get 600 updates per simulation's second if time acceleration is 0.1x, 60 for 1x, 6 for 10x, 0.6 for 100x, etc. If resolution is 1 update per 2 seconds, single firing of engine can cause uncontrollable spinning of the vessel.

Checking "Disable vertical sync." on Video tab of Orbiter Launchpad can improve calculations, since video frames will be rendered as fast as they can be, but they will be displayed on monitor with page tearing effect. But this can make 100x time acceleration usable for some autopilots.

You can also try set fixed time steps in Debugging options on Extra tab of Orbiter Launchpad, and check how the craft will react then. This way one rendered frame will correspond to set time step. However, I didn't check this option with autopilots.

And to Orbiter-Forum marcheenek.

 

[Grover]

RE:

you can also fix the problem, not for reentry, but it works great for any other maneuvers.

in the orbiter sound config (in the bottom right panel) there is an option to disable AP above 10x time warp, at 10x, i too only experience a slight wobble, but this prevents you accidentally using up all of your RCS fuel by accelerating to 1000x for a lunar transfer with prograde still enabled, then being stuck in an uncontrollable spin.

hope it helps!
-=Grover=-

 

[Xyon]

That has to be the best way I've seen that one explained, orb. :thumbup:

to Orbiter-Forum, marcheenek. I have nothing beyond what Orb said to tell you on this problem.