Chaff (electronic warfare)

In electronic warfare, which covers the entire electromagnetic spectrum chaff (electronic warfare) is a mass of radar-reflective material that acts as a decoy, reflecting the radar more brightly than the target.

The individual pieces of chaff, which are typically an aluminum film on plastic, need to be cut to dimensions related to the wavelength of the radar considered the greatest threat. There may be different chaff payloads to be used against missiles at different parts of their flight path; one type may be intended to distract midcourse guidance radar while another, final defense form, is intended to seduce the final attack. Chaff may be used in conjunction with other electronic warfare, such as deceptive jammers, and final hard-kill defense systems such as the RIM-116 Rolling Airframe Missile.

Current chaff dispensing usually is in an expendable cartridge that, once leaving the launcher, either bursts into a cloud or spreads as a stream. A shipboard family, for example, includes a RF seduction decoy (CHAFFSTAR), RF distraction decoy (LOROC), and infrred (HIRAM) and dual RF/IR seduction decoy (GEMINI). .

Historical forms
Earlier forms might be cut continuously from a roll, or, in the earliest forms, code-named Window by the Royal Air Force in the Second World War, literally thrown out as bundles.

On the night that the invasion fleet moved to the "D-Day" landings of Battle of Normandy, the Royal Air Force ran two deception operations using chaff to simulate false convoys; it is significant that 617 Squadron, usually considered the most accurate bombing squadron in the RAF, was committed to this mission:
 * Operation TAXABLE: 16 Lancasters of 617 Squadron approaching Cap d’Antifer.
 * Operation GLIMMER: 6 Stirlings of 218 Squadron directed at Boulogne.

During Operation LINEBACKER II of the Vietnam War, the initial use of chaff, in "corridors" dropped from chaff-laden fighters, did block specific radar beams, but served to mark the flight paths over which the following bombers would approach. One critical tactical change was changing from corridors to clouds.

Launchers
While they can be launched manually, military aircraft usually dispense chaff from magazine-loaded, increasingly intelligent expendable coutermeasures devices such as the AN/ALE-47. Such dispensers usually can release flare (electronic warfare) in a cartridge with the same form factor as the chaff, and even more expendable cartridges, such as radar jammers and intelligence sensors, are in the same package.

Surface vehicles, rather than dropping cartridges, usually shoot small rockets with warheads packed with chaff. The NATO standard form factors are:
 * 112 mm RBOC launcher
 * 130 mm SRBOC launcher