While the end explosive effect of the newer AIM-9X is pretty much the same as the current AIM-9M, the newer missile has a couple of important modifications that improve its chances of finding the target in the first place. An upgraded seeker design expands the seeker system's view, so it can locate targets well off boresight (in other words, targets that aren't right in front of the plane that's launching the missile).
A new thrust vectoring system gives the missile greater agility, allowing it to make sharp turns in mid-air. The basic idea is very simple: In addition to operating the flight fins, the guidance control system controls small vanes at the rear of the missile to divert the stream of hot gas from the rocket motor. By shifting the direction of the rocket's hot gas, the vanes use the thrust force to turn the missile. For example, when the vanes direct the gas to the right, the thrust pushes the back of the missile to the left, and the front of the missile turns to the right. This allows the missile to make very quick course adjustments to follow a fast target.
These modifications, as well as an improved guidance system and other technological additions, will update the Sidewinder so it stays competitive with new aircraft, ordnance and countermeasure technology. After half a century of active service, the Sidewinder should remain one of the dominate missile systems in the world for years to come.
For much more information about the Sidewinder and other missile technologies, check out the links on the next page.