In the video linked in this answer the spacecraft is said to be "gyroscopically balanced" (at about 00:20).

I'm going to ask about the terminology associated with the phrase "gyroscopic stabilization" - attitude control of a spacecraft which involves the use of gyroscopes.

Here is what I believe is true: A gyroscope is traditionally a rotating wheel in a mount that contains additional degrees of freedom. The term "scope" suggests some kind of measurement, and while a gyroscope can be a rotating wheel, it can also be a ring of optical fiber (or other waveguide) or a micro-fabricated Micro-electromechanical systems (MEMS) chip.

So if a spacecraft uses gyroscopes that do not contain rotating wheels, and it uses thrusters or magnetotorquers or solar reflectors for torque, can we still correctly say that it is gyroscopically stablized without the use of any rotating parts?

  • $\begingroup$ @Andreas OK that is good to know, thanks! $\endgroup$ – uhoh Oct 26 '16 at 11:51
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    $\begingroup$ The first use of the gyroscope was as an attitude sensor, that's why the name '...scope' is used. $\endgroup$ – Hobbes Oct 26 '16 at 12:46
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    $\begingroup$ @Andreas -- "Gyroscopic stabilization" does not describe the attitude sensor. It instead describes alternatives to attitude control thrusters that are based on rotating equipment such as momentum wheels, reaction wheels, reaction spheres, and control moment gyros. Control system engineers do use the term gyroscopic stabilization" (e.g., scholar.google.com/scholar?hl=en&q=gyroscopic+stabilization), but it appears to be more widely used in non-aerospace regimes. An example in aerospace: arc.aiaa.org/doi/pdf/10.2514/3.1898 . $\endgroup$ – David Hammen Oct 27 '16 at 13:55
  • $\begingroup$ @DavidHammen Yes, if I look at google scholar, I must admit many scientists speak of gyroscopic stabilized where I would have used gyro stabilized. That is a misnomer in my opinion, but thats how it is. I have deleted my misleading comment. +1 on your hint $\endgroup$ – Andreas Oct 27 '16 at 15:33

Gyroscopes used as sensors can be mechanical, ie with spinning parts, or electrical in which case lasers are often used. Movement is measured and the output is some sort of data which goes to a guidance system.

Gyroscopes used to provide physical force to stabilize or orient a craft have to be mechanical as the electric signals or lasers used in electronic gyroscopes have essentially no mass.

You are right that both can be used for stabilization, however for something to be called gyrostabilized it has to have the mechanical element providing the force changing orientation to be a gyroscope. At least that's the dictionary definition. Common usage seems to be a bit different calling anything gyroscopically stabilized if a gyroscope is involved at all. So it depends, I'd generally go with common usage.

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  • $\begingroup$ The last sentence needs some clarification. What do you mean by "mechanical element"? Could it be a thruster or magnetotorquer, or do you mean something massive and spinning? For example, here is a gyro-stablized camera system using a fiberoptic gyro and some motors, but no massive, spinning parts (as far as I can tell). $\endgroup$ – uhoh Oct 26 '16 at 12:33
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    $\begingroup$ Camera stabilization often works by moving a lens or the CCD to counteract the movement of the camera. This is an exception to the rule. For spacecraft, if it's called gyro-stabilized, you can count on there being a mechanical gyroscope. $\endgroup$ – Hobbes Oct 26 '16 at 12:44
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    $\begingroup$ Well, you can't have a non-mechanical device providing force to change orientation, so it would have to be for changing orientation. I've edited to make that clearer. $\endgroup$ – GdD Oct 26 '16 at 14:01
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    $\begingroup$ The 'mechanical gyroscope' will be there for adjusting the attitude. I expect nobody uses mechanical gyroscopes for measurement anymore. Electronic attitude sensors are simple and cheap. $\endgroup$ – Hobbes Oct 26 '16 at 14:03
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    $\begingroup$ Simple, cheap, light, more accurate, and they can't tumble or flip. $\endgroup$ – GdD Oct 26 '16 at 14:05

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