Gyro wheels how do they work?

[Everten P.]

Excuse the partial miracles reference but can someone tell me how those gyroscopic wheels work?

I heard scott manley talk about it and it interested me... It would also be nice if someone could tell me how the magic "navball" worked as well thanks...

[TheDarkStar]

Gyro wheels store angular momentum, from what I understand. Real life things similar to the navball indicate direction based on what the gyros say (probably by measuring how fast they go).

Someone who actually knows this in detail should say a bit more on this.

[Brotoro]

A spinning gyroscope has a lot of angular momentum, and it therefore resists if you try to turn its axis in a different direction. If you have a sufficiently massive gyro or set of gyros on a spaceship, then applying torques to their axes will result in equal an opposite torques being applied to the spacecraft, thereby turning the craft. KSP rather exaggerates this effect, giving us quite powerful torque to control the attitude of our spacecraft.

The navball is linked to a set of three gyros that have their axes pointed in perpendicular directions that provide a stable platform in space. As the spacecraft rotates around in space, this stable platform (mounted in pivoting rings) maintains its orientation in space...and its orientation relative to the spacecraft is displayed by driving the orientation of the navball.

In real spacecraft, such as Apollo, it was necessary to periodically synchronize the position of the stable gyro platform to the outside universe by sighting on stars.

Edited April 29, 2014 by Brotoro

[Seret]

Ok, first thing you need to understand: gyros are weird. They behave in odd counterintuitive ways. If you've ever held one in your hand you'll know what I mean. They react to an applied torque with a torque in a completely different direction.

Essentially all gyros are just a device in which something has some rotational movement, and which generates a measurable signal when an external torque is applied to it.

There are a few different kinds:

Traditional gyros

Basically just a wheel that is driven by a motor. In fact any wheel works as a gyro, it's gyroscopic forces that help bicycles and motorbikes stay up (or lean into corners). If you mount one inside three sets of gimbals it can be set up so that it always points in the same direction no matter how the thing it's attached to moves. That's a gyrocompass, which are still used on things like ships. They're very accurate but big, bulky and slow to initialize.

Strapdown gyros

These don't need gimbals, they're used in sets of three mounted in the x,y, and z directions and move with the thing they're attached to. The main kind are ring laser gyros, this is what modern aircraft and spacecraft use. They shoot two lasers in opposite directions around a ring in such a way that they set up a standing wave when they interfere. If something makes the gyro spin it will ever so slightly change the wavelength of the lasers and that shows up as a change in the standing wave.

Ring laser gyros have the advantage of not using gimbals, so don't suffer from gimbal lock, they're faster to set up, lighter and more compact. They aren't as accurate as spinny gyros though, and aren't north-seeking, so they can only tell you how you've moved, which is not quite the same as knowing exactly which way you're facing. In practice that means the system needs to get an accurate fix from something like GPS every so often to zero the errors.

The other kind of strapdown gyro you're likely to see is a miniaturized vibrating gyro. These don't actually spin at all, they just vibrate a tiny rotor back and forth, but they're able to detect torque the same way as any gyro. They can be made very, very small. So small they're built in silicon chip foundries and you can package one up complete with all of its control electronics into a single chip. They're commonly used for things like roll over sensors in cars and electronic spirit levels.

Edited April 29, 2014 by Seret

[Randox]

Might enjoy this video explaining and demonstrating gyroscopes. Pretty short too:

Edited April 29, 2014 by Randox

[lajoswinkler]

Excuse the partial miracles reference but can someone tell me how those gyroscopic wheels work?

I heard scott manley talk about it and it interested me... It would also be nice if someone could tell me how the magic "navball" worked as well thanks...

Consider how difficult it is to change the inclination of an orbiting body. It generally wants to stay in its orbit. Gyroscope's ring particles are in a similar condition, except they're all connected, and instead of gravity, electric force is keeping them connected to the axis (atomic bonds). When you spin the ring, there is no reason why it would change the axis of spinning. It "wants" to stay in its determined axis of rotation, and any attempt to change the "orbits" of particles in the ring results in the need of energy, which is being shown as a resistive force.

[Everten P.]

Awesome! You guys never cease to amaze me in your cooperation

[Yasmy]

Here's a neat demonstration of reaction wheels:

Edited May 6, 2014 by Yasmy

[FREEFALL1984]

I need a Cubli, who do I throw my money at

[bsalis]

I need a Cubli, who do I throw my money at

I want two!

When i first saw this video i checked, and quickly googled again now. Sadly, i don't think they are mass produced for sale.

These guys created them for research: http://www.idsc.ethz.ch/Research_DAndrea/Cubli

[HeadHunter67]

Might enjoy this video explaining and demonstrating gyroscopes. Pretty short too:

I'm surprised that so many people here on the forum seem to never have done this experiment in high school science. I've heard people on the forums and Facebook imply that they think a spacecraft reaction wheel violates Newton's Third Law somehow.

It's more fun with an office chair!

[magnemoe]

A spinning gyroscope has a lot of angular momentum, and it therefore resists if you try to turn its axis in a different direction. If you have a sufficiently massive gyro or set of gyros on a spaceship, then applying torques to their axes will result in equal an opposite torques being applied to the spacecraft, thereby turning the craft. KSP rather exaggerates this effect, giving us quite powerful torque to control the attitude of our spacecraft.

The navball is linked to a set of three gyros that have their axes pointed in perpendicular directions that provide a stable platform in space. As the spacecraft rotates around in space, this stable platform (mounted in pivoting rings) maintains its orientation in space...and its orientation relative to the spacecraft is displayed by driving the orientation of the navball.

In real spacecraft, such as Apollo, it was necessary to periodically synchronize the position of the stable gyro platform to the outside universe by sighting on stars.

KSP reaction wheels are more powerful than the real world ones used in space, this is for gameplay reasons. Only manned craft who uses them are IIS. Another issue is that you can use ksp reaction wheels to offset an unbalanced ship powered by engines without gimbal, this does not work as the wheel would have to spin up faster and faster.

rotating and stopping however avoid this, you spin up gyro, this cause you to rotate and you then brake the gyro then you point the right direction.

[RuBisCO]

KSP reaction wells do not suffer from momentum "saturation": they seem to be able to spin up to infanite speeds and thus absorb a infinite amount of momentum. I always hope for a KSP mod or update to fix this such that you soon need to us RCS to neutralize built up monentum. In the mean time its a simple matter of change .cfg file setting to make reaction wheels of command pods more realistic and much weaker.

Another thing about real life reaction wheels is they tend to fail! Often spaceships (Kepler Space Telescope the most recent example) often need the wheels to spin for years to hold orientation perfectly, the bearings eventually fail. The solutions is more expensive bearings or magnetic bearings which experience nor physical wear. There is already a mod with things breaking down a reaction wheels should be one of them, again spaceships often have spare wheels, just 3 are needed, but an extra is always added for take over for any of the others if they fail.

Edited May 7, 2014 by RuBisCO

[Seret]

Do they really need to be more realistic though? Adding simulation that only makes the game more frustrating to play is fine for a hardcore simulator, but I don't think KSP needs to go there.

[RuBisCO]

Do they really need to be more realistic though? Adding simulation that only makes the game more frustrating to play is fine for a hardcore simulator, but I don't think KSP needs to go there.

Then we should have a difficulty setting so as to provide both the new players an easy experience and the experienced players more challenging calliope.