Gyroscopes
can be very perplexing objects because they move in peculiar ways and even seem
to defy gravity. These special properties make gyroscopes extremely important in
everything from your bicycle to the advanced navigation system on the space
shuttle. A typical airplane uses about a dozen gyroscopes in everything from its
compass to its autopilot. The Russian Mir space station used 11 gyroscopes to
keep its orientation to the sun, and the Hubble Space Telescope has a batch of
navigational gyros as well. Gyroscopic effects are also central to things like
yo-yos and Frisbees!
The effect of all this is that, once you spin a gyroscope, its axle wants to keep pointing in the same direction. If you mount the gyroscope in a set of gimbals so that it can continue pointing in the same direction, it will. This is the basis of the gyro-compass.
If you mount two gyroscopes with their axles at right angles to one another on a platform, and place the platform inside a set of gimbals, the platform will remain completely rigid as the gimbals rotate in any way they please. This is this basis of inertial navigation systems (INS).
In an INS, sensors on the gimbals' axles detect when the platform rotates. The INS uses those signals to understand the vehicle's rotations relative to the platform. If you add to the platform a set of three sensitive accelerometers, you can tell exactly where the vehicle is heading and how its motion is changing in all three directions. With this information, an airplane's autopilot can keep the plane on course, and a rocket's guidance system can insert the rocket into a desired orbit!
If you have ever played with toy gyroscopes, you know that they can perform all sorts of interesting tricks. They can balance on string or a finger; they can resist motion about the spin axis in very odd ways; but the most interesting effect is called precession. This is the gravity-defying part of a gyroscope
This
mysterious effect is precession. In the general case, precession works like
this: If you have a spinning gyroscope and you try to rotate its spin axis, the
gyroscope will instead try to rotate about an axis at right angles to your force
axis, like this:
In figure 1, the gyroscope is spinning on its axis. In figure 2, a force is applied to try to rotate the spin axis.In figure 3, the gyroscope is reacting to the input force along an axis perpendicular to the input force.
Jeff Danger, Science
Ranger
Cool Science Show For Kids