Sea-skimming

Sea skimming is a technique many anti-ship missiles and some fighter or strike aircraft use to avoid radar and infrared detection during their approach.

Sea skimming anti-ship missiles try to fly as low as is practically achievable, which is almost always below 50 meters (150 ft), and is often down towards 5 meters (15 ft). When under attack, a warship can detect sea-skimming missiles only once they appear over the horizon (about 28 to 46 km from the ship), allowing about 25 to 60 seconds of warning.

By flying low to the sea, missiles decrease the range at which the target ships can detect them by a significant amount. Flying at a lower altitude increases the amount of time the missile is under the horizon from the perspective of the target ship, making it harder to detect due to radar clutter from the sea and similar effects. The real-life success of sea skimming depends on its exact implementation, the sophistication of the detection equipment, as well as the infrared and radar signature of the missile. Sea skimming can significantly reduce the available response time that a ship's missile defenses have to work within, making these missiles significantly harder to defend against. Sea skimming can also increase the range of a missile, by relying on ground effects.

The use of sea skimming increases the risk of water impact with the missile before reaching the target, due to weather conditions, rogue waves, software bugs and other factors. Sea skimming also hinders target acquisition, as many of the principles that hinder the target's detection of the missile also hinder the missile's detection of the target. Furthermore, sea skimming involves a significant computational load, increasing the required processing power and cost.

The Phalanx CIWS (close-in weapons system) is an automated, high speed defense against anti-ship missiles, designed and manufactured by General Dynamics (now a part of Raytheon). Consisting of a radar-guided 20 mm (0.79 in) Gatling gun mounted on a swiveling base, the Phalanx is used by the United States Navy on every class of surface combat ship, by the United States Coast Guard aboard its Hamilton-class and Legend-class cutters, and the navies of 16 allied nations. Its effective range is very short relative to the range of modern ASMs, from 1 to 5 nautical miles (9 km).

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