The Seagnat Control System (sometimes spelled SeaGnat or Sea Gnat) is a British decoy system produced by Chemring Countermeasures Ltd used on many NATO warships to safeguard against incoming missiles.
- Mk214 Seduction Chaff
- Mk216 Distraction Chaff
- Mk245 "GIANT" IR Round
- Mk251 "siren" Active Decoy Round (only on later "DLH" versions)
The rounds are launched as decoys to trick incoming missiles into missing the ship or to prematurely detonating.
Rounds are launched from NATO standard 130mm launchers, either fixed or trainable, and typically mounted in groups of around six barrels.
The Active Decoy Round has three phases: a low g rocket motor to project it away from the ship, a drogue to slow the round, and a para-sail wing that allows the decoy to slowly maneuver as it descends to the water. The device is 125mm diameter by 1m long. It is powered by a thermal battery and its on-board computer allows the transmitters to radiate in either deception mode or noise (smart or barrage). Range is up to 500m from the ship.