By Tom Harris
Harris, Tom. "How Sidewinder Missiles Work." 03 October 2002. HowStuffWorks.com. 26 February 2010.
The Sidewinder AIM-9 (air intercept missile 9) is a short-range, air-to-air missile. It is launched an airborne aircraft and used to take down an enemy aircraft Missiles like the Sidewinder are called smart weapons because they have built-in seeking systems that let them home in on a target.
The technology of smart weapons really evolved following World War II. Early guided weapon prototypes were usually built around radar technology, which was expensive and problematic. Pilots had to keep their aircraft in a vulnerable position after firing in order to keep a radar lock on the enemy until the missile could find it. Most of these missiles had a nearly 90 percent failure rate.
In 1947, a Naval physicist named Bill McLean took it upon himself to build a better system -- a missile that would seek out the heat from an enemy aircraft's engine system. Since the missile would home in on the target's own emitted energy, rather than reflected radio energy, the pilot could "fire and forget" -- that is, he could launch the missile and get clear. In place of the bulky radar equipment, the missile would use a relatively small heat-sensing photovoltaic cell to "see" the target. This meant it could be built much smaller than the current radar prototypes, and at a much lower cost.
Officially, the Navy had no interest in non-radar guidance systems, but at the China Lake, California, Naval Ordnance Test Station (NOTS) where McLean was employed, researchers had enough freedom to pursue unconventional projects. Under the guise of missile fuze development, McLean and his colleagues worked out the design of the first Sidewinder prototypes. Six years later, in September 1953, the missile had its first successful test run.
Since then, the Sidewinder has taken many different forms, each model adding new technology and capabilities. While today's semiconductor guidance systems are much more advanced than the vacuum tubes on the originals, the Sidewinder's operation is pretty similar.
The central idea of the Sidewinder system is to home in on the heat, or infrared energy, emitted by an enemy aircraft's engine exhaust or hot fuselage. To accomplish this, the Sidewinder uses nine major components:
- A rocket engine that burns a low-smoke solid propellant material, provides the thrust required to propel the missile through the air
- Rear stabilizing wings, outfitted with a stabilizing rollerons (similar in design to a pinwheel), which provide the necessary lift to keep the missile airborne
- A seeker, something like the CCD in a video camera, which detects the infrared light from the target; this may be coupled with a conical scanning system to scan a large section of the sky
- Guidance control electronics, which process information from the seeker to calculate the proper course for the missile
- A control actuation section, which adjusts flight fins near the nose of the missile based on instructions from the guidance electronics
- Flight fins, which steer the missiles through the air by generating drag (wind resistance) on one side of the missile, causing it to turn in that direction
- A warhead that explodes when the Sidewinder is very close to its target
- A fuze system that triggers the warhead explosion when the missile reaches its target
- A battery to provide power to the onboard electronics
Newer missiles have a couple of important modifications that improve their chances of locating a target in the first place. An upgraded seeker design expands the seeker system's view, so it can locate targets well off boresight. A thrust vectoring system gives the missile improved agility, allowing it to make sharp turns in mid-air. 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.
