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Detumbling is a common problem and challenge for satellite operators during Launch and Early Orbit Phase (LEOP), with a common cause being a tip-off rate induced during separation with the launch vehicle. Having been introduced to the industry however, I have come to encounter cases where satellites experience tumbling (to the point of safehold) even during operational phase, months after a successful LEOP and commissioning.

I would suspect that the form factor of the satellite would be a potential cause, since solar irradiation and atmospheric drag might impart an uneven rotational angular momentum to the satellite body?

On a side note, how do satellite operators typically recover from such incidents? Any examples out there?

Shawn Lim
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  • Wouldn't light pressure or atmo drag be extremely tiny forces? – Darth Pseudonym Mar 15 '24 at 14:16
  • "I have come to encounter cases where satellites experience tumbling (to the point of safehold) even during operational phase..." Could you provide some examples or source for these? – AJN Mar 15 '24 at 15:18
  • @AJN I can't really go into specifics given the security and reputational considerations involved with these organizations. What I can say its has a deployed form factor of around L600 x B600 x H300mm, weighing around 150kg, and inserted in a near equatorial orbit at an altitude of ~550-600km. I doubt providing further specifics would help anyway since these issues aren't publicly broadcasted – Shawn Lim Mar 15 '24 at 15:52
  • @DarthPseudonym Exactly why I'm so perplexed. Obviously it might simply be an operator mishap (e.g. propellant misfiring) that caused the tumbling, but I'm giving the benefit of doubt that other factors might be at play here. – Shawn Lim Mar 15 '24 at 15:55
  • Add torques arising from interaction with earth's magnetic field and gravitational field to the list of momentum sources. – AJN Mar 15 '24 at 17:15
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    https://science.nasa.gov/missions/swift/nasas-swift-temporarily-suspends-science-operations/ – John Doty Mar 20 '24 at 16:33

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The boring and probably most common reason for a unwanted tumble would be leak or otherwise uncommanded operation of the control system, noting this will generally end with fuel exhaustion or other failure of the system AND a high tumble rate (example Peregrine).

A related failure mode is where a sub system fails to operate (stuck valves or similar) removing one axis of control, in many cases this can be worked around by rotating the craft such that a working system is aligned with the needed axis but this can be complex to sequence and is possibly for a poorly structured set of commands to produce a tumble, further recovery from this tumble will may be hindered if the onboard fail safe recovery is trying to operate the failed axis to regain communication.

Where mechanical elements like propellant valves in a thruster are involved there will not be a binary 100% thrust for X time then stop result, instead some form of ramp up and taper off. This can change as platform ages and parts wear or tank pressures fall possibly resulting in oscillations around the desired pointing and higher consumable consumption.

Many craft do fine and ongoing control with reaction/momentum wheels, these however need to be unloaded/de-saturated periodically with a thruster based system, so a craft with working wheels but wonky thrusters may end up with periods of correct operation followed by tumbles that may or may not be recoverable.

As with Peregrine it is often possible for other parts of the system to compensate for a time until some resource or capability is consumed and then sudden obvious failure occurs. This is not an engineering problem but a business decision in how the owner communicates with public/customers about the issue. With the various issues on Hubble the information was public so the various failures of redundant but interlinked systems are known and understood, where a private company might be more opaque and seemingly 'better'.

Other factors that can complicate vehicle stability:

GremlinWranger
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