What's inertial navigation (IN) in missile? What's the key component used for IN?

Answer 1

For something as simple as a gyroscope, the mathematics is incredibly complex. It involves vector analyses, matrices, and partial differential equations to solve the forces created by what amounts to a spinning top.

Suffice it to say that, when a force is applied to a gyro (like if a missile tries to stray from a straight line) the gyro detects that force and, through the complex math, reacts with an equal and opposite counter force to get it back in line. (By the way, it is just this effect that keeps a spinning top upright. It is also this gyroscopic effect that makes keeping a two-wheeler bicycle upright easier.)

In general, a missile needs one gyro per dimension...three altogether. Precession is where the gyro doesn't quite offset the forces applied to it and the top wobbles around (precesses) a bit. As a consequence, the required trajectory is not met unless some corrections are made en route to the target.

Nowadays, guided missiles use GPS to update the gyro settings and offset the precesion it would otherwise have. As a consequence the circular error probable (CEP) of ICBMs and the like is much smaller than they used to be. And as a further consequence, that means the explosive power of the warhead can be considerably less than they used to be and still have reasonable assurance of a target kill.

Answer 2

They can either use gyros, or use a laser ring gyro, which fires a laser through a prism and can detect movement by timing the light through the prism.
The regular gyro has alot of precession which means that its not going to be accurate near the end of its flight, which accounts for the most reliabIe ICBM's only being accurate to about 400 yards and older missiles being incredibly inaccurate, but its pretty good for something that just flew 10,000 miles.

Answer 3

It is a method of navigation that depends upon the inertia of a spinning gyroscope to detect changes in direction. A rapidily spinning disk resists changes of its direction other than along the axis of rotation. The resistance can be measured, showing the acceleration of the missile, and therby giving its tejectory.