U.S. Warship Strikes Over the Horizon With Help From Unmanned Systems

The U.S. Navy destroyer USS John Finn trialed a new, stealthier method of attack on Tuesday, firing off a missile at a faraway surface target without ever turning on her fire control radar. 

The test was conducted as part of the Navy's unmanned systems battle problem exercise, UxS IBP 21 - a first-of-its kind operation that is intended to give the service a better idea of how it can integrate remotely-operated and autonomous vessels, subs and aircraft into the manned fleet. 

In the over-the-horizon missile trial, manned and unmanned surface vessels and aircraft took bearings on a radio signal from the surface target using passive means, then relayed the data back to the destroyer. John Finn's crew used a "fused" picture generated from that information to engage the target with an SM-6 missile at a range "well beyond the line of sight." No active radar systems were employed. 

"It was totally passive where we didn’t have active sensors on target,” Carrier Strike Group 3 commander Rear Adm. James Aiken told USNI. "We were able to track it because of the [radio signal] that was coming off the target, develop lines of bearing, then launch the missile.”

The SM-6 is an anti-aircraft missile with a secondary anti-ship capability, and it has an estimated range of about 250 nm (the true maximum range is classified). 

The value of passive long-range target detection is in stealth. The U.S. Navy's surface combatants carry powerful radar systems for precision targeting, but as soon as that radar is turned on, the vessel is effectively broadcasting its own position - and providing a homing beacon for the enemy. With expendable unmanned platforms - drone boats, aircraft and subs - positioned over the horizon, the Navy's destroyers and cruisers could offboard the task of target acquisition and tracking. This would give them a better chance of avoiding anti-ship missile fire while engaging the enemy.