The AIM-9 Sidewinder is one of the oldest, most affordable, and most successful air-to-air missiles, having caused at least 270 kills globally to date.
Guidance and Control Section Composition
The guidance and control section of the Sidewinder is composed of three main components:
1. Infrared Seeker Assembly: Detects the target.
2. Electronic Assembly: Converts the detected target information into tracking and guidance command signals.
3. Gas Servo Assembly: Comprises a gas generator, manifold, pistons, rocking arms, solenoid valves, and thermal battery. This assembly converts electrical guidance commands into mechanical movements of the control fins. Four control wings attached to the guidance and control section provide aerodynamic lift and direction changes during free flight. These movable surfaces are electrically controlled and operated automatically by the gas servo assembly.
Umbilical Cable
The missile's umbilical cable, also connected to the guidance and control section, facilitates the exchange of electronic signals and cooling gas between the missile and aircraft before launch.
Reticle Infrared Seeker Composition
The front end of the missile is made of glass lenses rather than a steel warhead. One of the most critical components is the reticle infrared seeker, a common optical system design in traditional heat-guided missiles. This system comprises:
- A primary mirror and a reticle infrared detector.
- A flat secondary mirror.
In its simplest form, the reticle consists of two parts, one half-transparent and the other half-opaque, arranged in this manner.
Working Principle of the Infrared Seeker
The reticle infrared seeker operates as follows:
- A heat source enters through a set of lenses into the rotating reticle around its axis, which itself also rotates circumferentially.
- Infrared light will flicker at the point marked on the reticle.
- This maps the path relative to the retinal axis, generating signals of different phases and amplitudes.
Conversion of Infrared Signals to Sound Pulses
A key component of the seeker is the dichroic filter, which isolates and passes the desired infrared wavelength. The sensor will only detect the infrared source during the transparent portion of the reticle, producing a periodic pulse sequence of a specific frequency. If the missile is within its line of sight, the pulses emit a distinct sound.
Upgraded AIM-9X
The AIM-9 Sidewinder missile will be upgraded to the AIM-9X over the coming decades. The AIM-9X is slightly smaller compared to the older version. When placed side by side, the AIM-9X features a thrust vector control system on the rear, unlike the fixed nozzle of the older version. The AIM-9X has independently rotating tail fins, whereas the older version only has rollerons for stability.
AIM-9X Specifications
- Range: 35 kilometers
- Speed: Mach 2.5
The AIM-9X integrates many components from older Sidewinder versions, including the rocket motor, warhead, and active optical target detector. Despite this, its performance far exceeds older Sidewinders, featuring a solid-propellant rocket motor, approximately 3 meters in length, and a launch weight of 84.3 kilograms. Its range and speed are classified, but it is expected to reach 35 kilometers and achieve a speed of 2.5 Mach.
Sidewinder Missile Operation
Using Older Versions of the Sidewinder:
Step 1: The pilot must chase the target and only release the missile upon hearing the maximum sound peak, which is derived from the enemy's infrared heat signal.
Step 2: The missile ignites its solid rocket motor and launches towards the target.
Step 3: As the missile accelerates in the air, the airstream spins the tail rollerons, stabilizing the missile in flight by acting as gyroscopes against rotational forces.
Step 4: Servo pumps and pistons adjust the canards to compensate for the target's evasion from the center.
Step 5: The missile is designed to overcompensate and move to the guided position of the target rather than chasing the aircraft.
Step 6: Upon reaching the target, the proximity fuse triggers the 9.36-kilogram annular blast fragmentation warhead, pushing metal fragments outward in a ring pattern, destroying any aircraft in its path.
AIM-9X and IIR Seeker
Older versions of the Sidewinder sometimes locked onto the sun or flares deployed by aircraft rather than enemy planes. The AIM-9X uses an infrared camera to take photos seen by the seeker and then uses computer algorithms to confirm the target. The IIR seeker can recognize the shape of aircraft and compare it with a database, enhancing tracking capability. Once locked on, it can avoid flares and successfully hit the target.
