Rotation slowdown

Ajaja

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Can someone explain why rotation of DG in this scenario slowdowns in Orbiter and stops after few days (at x1000)? Orbiter v111105, all realism and perturbation check-boxes switched on. Is it real physical effect or bug of the Orbiter?

Code:
BEGIN_DESC
Contains the latest simulation state.
END_DESC

BEGIN_ENVIRONMENT
  System Sol
  Date MJD 51984.6193805043
END_ENVIRONMENT

BEGIN_FOCUS
  Ship 1
END_FOCUS

BEGIN_CAMERA
  TARGET 1
  MODE Extern
  POS 6.29 87.43 168.01
  TRACKMODE GlobalFrame
  FOV 60.15
END_CAMERA

BEGIN_HUD
  TYPE Surface
END_HUD

BEGIN_SHIPS
1:DeltaGlider
  STATUS Orbiting Moon
  RPOS -21383.43777466 -1845179.64788319 20424.66085243
  RVEL 1152.91890578 -26.09960045 -1151.95106142
  AROT 177.34961990 -86.21468711 167.64336454
  VROT 0.00048558 0.00023087 -206.39536863
  AFCMODE 7
  PRPLEVEL 0:0.03642400 1:0.01158935
  NAVFREQ 0 0 0 0
  XPDR 0
  AAP 0:0 0:0 0:0
END
END_SHIPS
 

insane_alien

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I suppose you have gravity gradient torque turned on?

if you do then that's why.

It's tidal locking which really does happen in reality. The moon is tidally locked for instance. although it took a lot longer than it would take for a delta glider or space shuttle.
 

Ajaja

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Yes, but killing 200 deg/s rotation for 2 days by gravity gradient torque at Moon orbit - it's little unbelievable.
 

TSPenguin

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Might be exaggerated by time acceleration. Anyone got a spare rig to let this run for two days?
 

martins

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You could run it in orbiter_ng without a client. Should give frame rates in the vicinity of 10^4Hz, so even 100x time acceleration would still provide step sizes around 10^-2s.
 

agentgonzo

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It's tidal locking which really does happen in reality. The moon is tidally locked for instance. although it took a lot longer than it would take for a delta glider or space shuttle.
It won't be tidal locking in orbiter. Tidal locking is a consequence of deformation of the body along with gravity-gradient torque.
 

martins

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It won't be tidal locking in orbiter. Tidal locking is a consequence of deformation of the body along with gravity-gradient torque.

It will, because orbiter supports a damping term to the angular moments, which lumps all effects like deformation and sloshing. It may be set too high for the DeltaGlider. You could try playing around with this.

Any information on how long a space shuttle would need to tidally lock in a typical Earth orbit if starting from an inertial frame and leaving it to its own devices?
 

agentgonzo

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It will, because orbiter supports a damping term to the angular moments, which lumps all effects like deformation and sloshing.
I did not know that!

Any information on how long a space shuttle would need to tidally lock in a typical Earth orbit if starting from an inertial frame and leaving it to its own devices?
I would guess a very very long time. The amount of torque that causes tidal locking is related to the size of the tidal bulges. In the space shuttle these bulges are going to be absolutely tiny due to the small size of the shuttle and its rigidity. But then again the lower mass will mean that it requires less torque to turn.

I don't know whether these two effects cancel out, but my gut feeling is that they don't and the shuttle would take longer to tidally lock (this is different to gravity-gradient stabilization) than, say, our moon. I wouldn't be surprised if the time for the shuttle to tidally-lock if left to its own devices (and negating drag) was greater than the age of the universe.
 
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