# Gyros and Space **URL:** \ **Category:** Factual Questions\ **Created:** [December 7, 2002, 9:10am UTC](https://boards.straightdope.com/t/gyros-and-space/141116 "2002-12-07T09:10:09Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Daylon](https://avatars.discourse-cdn.com/v4/letter/d/45deac/32.png) [@Daylon](https://boards.straightdope.com/u/Daylon)\ **Post date:** [December 7, 2002, 9:10am UTC](https://boards.straightdope.com/t/gyros-and-space/141116/1 "2002-12-07T09:10:09Z")
Okay…probably a stupid question…but would a gyroscope exhibit the same effects without gravity? I remember doing the “spinning bicycle wheel” thing in physics class as a kid…when you pulled up and tried to get it spinning vertically, it would jerk to the right. (Due to centripetal force we are told) Here’s the question…would it do that in space as well? Or is that a function of gravity? (Again…sorry for a stupid question) D. ---
**Author:** ![Broomstick](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/broomstick/32/246_2.png) [@Broomstick](https://boards.straightdope.com/u/Broomstick)\ **Post date:** [December 7, 2002, 12:19pm UTC](https://boards.straightdope.com/t/gyros-and-space/141116/2 "2002-12-07T12:19:39Z")
That’s not a stupid question. The answer is: gyroscopes work just as well in space and microgravity as on earth in macro gravity. I do wish to clarify one other item, though - you mention spinning a bicycle wheel (a type of gyro, in this case), pulling it up, and having it pull to the right. That was NOT “centripetal” force at work, but something called “precession”. It does have to do with the spinning, but I don’t have the greatest understanding of it so I won’t try to explain further. Nor does it have anything to do with gravity. ---
**Author:** ![Shade](https://avatars.discourse-cdn.com/v4/letter/s/2bfe46/32.png) [@Shade](https://boards.straightdope.com/u/Shade)\ **Post date:** [December 7, 2002, 12:19pm UTC](https://boards.straightdope.com/t/gyros-and-space/141116/3 "2002-12-07T12:19:42Z")
AFAIK a gyroscope (aka spinning disk) in space will naturally continue to spin. For instance, the earth? ---
**Author:** ![3waygeek](https://avatars.discourse-cdn.com/v4/letter/3/e95f7d/32.png) [@3waygeek](https://boards.straightdope.com/u/3waygeek)\ **Post date:** [December 7, 2002, 3:03pm UTC](https://boards.straightdope.com/t/gyros-and-space/141116/4 "2002-12-07T15:03:51Z")
Yes, gyros work in space, if they’re built to handle the rigors of spaceflight. Many years ago, I worked for a [company](http://www.condorpacific.com/) that made gyros and inertial navigation systems. One platform for our gyros was the Hughes HS601 satellite, used by DirecTV. For more info about gyros than any sane person would need to know, check out _Über die Theorie des Kreisels_ by [Klein](http://scienceworld.wolfram.com/biography/KleinFelix.html) & [Sommerfeld](http://scienceworld.wolfram.com/biography/Sommerfeld.html). Somehow, they managed to write **4 volumes** on the subject. For a less exhaustive overview, check out Goldstein’s _Classical Mechanics_. ---
**Author:** ![Podkayne](https://avatars.discourse-cdn.com/v4/letter/p/edb3f5/32.png) [@Podkayne](https://boards.straightdope.com/u/Podkayne)\ **Post date:** [December 7, 2002, 5:09pm UTC](https://boards.straightdope.com/t/gyros-and-space/141116/5 "2002-12-07T17:09:01Z")
It’s actually really cool . . . they use gyros to stabilize spacecraft, spinning them up or spinning them down to counteract the spacecraft’s motion. This is all accomplished using electrical motors, so they don’t have to use rocket fuel, which will eventually run out. On average all the little corrections cancel out, but sometimes the gyros end up spinning too fast, so they have to do a “dump” where the spin is transferred back to the spacecraft, and they burn the navigational rockets to stop the spacecraft from spinning again. I don’t know why I find that so cool. I just do. ---
**Author:** ![Qadgop\_the\_Mercotan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/qadgop_the_mercotan/32/83_2.png) [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)\ **Post date:** [December 7, 2002, 5:22pm UTC](https://boards.straightdope.com/t/gyros-and-space/141116/6 "2002-12-07T17:22:55Z")
I am getting _too_ far away from my science background, and too close to my self-indulgent side. When I read the OP title, for the life of me, I could not make the connection between a tasty greek sandwich and the final frontier. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [December 7, 2002, 5:34pm UTC](https://boards.straightdope.com/t/gyros-and-space/141116/7 "2002-12-07T17:34:49Z")
> [@](#): > > \*Originally posted by Podkayne \* > **…they use gyros to stabilize spacecraft, spinning them up or spinning them down to counteract the spacecraft’s motion.** Those are called reaction wheels or momentum wheels. They are simple motor-driven wheels mounted on a fixed axis. The term “gyro” (gyroscope) referes to something else, namely a spinning wheel used as a sensor to detect (not change) the orientation of the spacecraft. Most spacecraft use gyros to measure the attitude and reaction wheels to change the attitude. You don’t have to use fuel to “dump” the angular momentum that builds up on the reaction wheels. You can simply turn on an electromagnet and push against the magnetic field of the earth. Such a device is called a magnetic torquer, and most low-earth orbit satellites use them. Getting back to the OP, yes, gyros work in zero gravity. But there is one popular experiment which works because of gravity: hold a wheel with the axis horizontal, spin up the wheel, and support only one end of the axis. The axis will spin around (precess). This happens because gravity pulls the wheel down, but the gyroscope converts this vertical pull into a horizontal push so the axis moves around.