AIM-9 fin question

[Bucic]

What is this marked element?

[Griffin]

A rolleron:

A spinning wheel resists lateral forces acting on it. In this case, the gyroscopic motion counteracts the missile's tendency to roll -- to rotate about its central axis. The simple, cheap rollerons steady the missile as it zips through the air, which keeps the seeker assembly from spinning at top speed. This makes it a lot easier to track the target

http:http://science.howstuffworks.com/sidewinder4.htm

[Woodstock]

http://en.wikipedia.org/wiki/AIM-9_Sidewinder

...

However this system also requires the missile to have a fixed roll axis orientation. If the missile spins at all, the timing based on the speed of rotation of the mirror is no longer accurate. Correcting for this spin would normally require some sort of sensor to tell which way is "down" and then adding controls to correct it. Instead, small control surfaces were placed at the rear of the missile with spinning disks on their outer surface, these are known as rollerons. Airflow over the disk spins them to a high speed. If the missile starts to roll, the gyroscopic force of the disk drives the control surface into the airflow, cancelling the motion. Thus the Sidewinder team replaced a potentially complex control system with a simple mechanical solution.

[Bucic]

I'm surprised that such details are described on Wikipedia :) Thanks.

[DamianJG54K]

This was really interesting. Didn't know about that.

[Bucic]

BTW, who would have thought that we'll see such details on 3D models in flight sims. The picture I a LO FC 2 screenshot :) http://lockon.co.uk/index.php?end_pos=1671&scr=default#3d