When the Arleigh Burke-class guided-missile destroyer USS Mason (DDG 87) came under attack multiple times in October 2016, the ship was able in at least one instance to use its defenses to shoot down the incoming Noor anti-ship missiles.
But there are times when a ship can't shoot down the missiles – and thankfully, U.S. Navy vessels have plenty of options.
There are a number of reasons why a U.S. Navy ship may not be able to fire. In some cases, it may be due to restrictive rules of engagement. Other times, the inability to shoot may be due to battle damage. Perhaps there's concern about what a miss might do.
In those cases, the Navy relies on decoying an inbound missile in one of several ways.
The guided-missile destroyer USS Mason (DDG 87) steams through the Atlantic Ocean. Mason is participating in Joint Task Force Exercise (JTFEX) 08-4 as part of the Theodore Roosevelt Carrier Strike Group. (U.S. Navy photo by Mass Communication Specialist 2nd Class Katrina Parker /Released)
One option is via electronic countermeasures, or "ECM." Specifically, the goal is to interfere with the guidance systems on the missiles by confusing or blocking the seekers on radar-guided ones.
The confusion angle is very simple. An ECM system like the AN/SLQ-32 would create false targets. This gets the missile to hopefully chase into empty ocean. Another method is to reduce the seeker's effective range with jamming. This would allow the ship to get outside the seeker's ability to acquire a target — again sending the missile off on a merry chase to nowhere.
An antenna for the AN/SLQ-32 system on board USS Nicholson (DD 982). (US Navy photo)
However, missile makers are wise to the countermeasures and haven't stood still. The field of electronic counter-countermeasures exists to help make seekers both more powerful and more intelligent, enabling them to beat the ECM. Thankfully, there is another option.
Most U.S. Navy ships also have launchers for chaff. Like the deception portion of ECM, it creates a false target for a missile seeker. Unlike the deception portion of ECM, since it is actually physically metal, it creates a real "target" for the seeker to home in on.
Furthermore, firing a bunch of the rockets makes a bigger "target" – which the incoming missile will hopefully go for.
You can see a Burke-class destroyer launch a chaff rocket in the video below.
During the Argentinean air attacks on the Royal Navy on May 25, 1982, a Royal Navy frigate, HMS Ambuscade, fired off chaff to decoy incoming Exocet anti-ship missiles. The missiles flew through the chaff cloud and locked on to the Atlantic Conveyor, a merchant vessel carrying supplies for the British forces. Two missiles hit the vessel, which sank three days after being hit.