The U.S. Navy, aiming to make its attack submarines even more stealthy and lethal at extended ranges, took a big step forward with a contract announcement Tuesday.

The Office of Naval Research awarded Aerojet Rocketdyne a contract that aims to increase the efficiency of the engine of its Mark 48 heavyweight torpedo, a weapon designed to kill deep-diving Soviet submarines and advanced surface ships, according to a release from the company

The award, worth $2.6 million, will go toward developing a prototype engine that gets more bang for the buck out of the Navy’s standard Otto fuel propellant. If awarded, the second phase of the program would integrate the engine into a full-scale propulsion system, the announcement said.

The award is part of ONR’s Torpedo Advanced Propulsion System project, which has some lofty ambitions attached to it, said Bryan Clark, a former submarine officer and analyst with the Center for Strategic and Budgetary Assessments.

The idea behind extending the range of the torpedo is to keep valuable submarines away from potential targets and allow a third party (a P-8 Poseidon overhead, for example) to relay the targeting data, Clark said.

“Through third-party targeting, you can use it as a standoff weapon,” he said. “If you can extend that range to 50 or more miles, you can attack submarines without your sub having to hold that target organically with its sensors.”

At those ranges, it’s unlikely the submarine would give away its position by firing a torpedo, he said. Using this method, he added, the service can get the most out of the weapons packed on the attack boat.

“If you have 30 torpedoes onboard, you may only have one or two targets within range of your sensors and weapons,” Clark said, arguing that with third-party targeting, one could conceivably use the submarine as a submerged arsenal.

The concept is similar to the cooperative engagement technology that the surface navy is developing, where an aircraft such as an F-35 or E-2D detects an incoming hostile track and relays kill-quality target data to the ship for engagement with a long-range missile, such as an SM-6.

The technology allows ships to remain stealthy by keeping off its big air-warfare radars, and instead relying on airborne sensors for targeting data.

Applying the same concept to the submarine world still has some issues, however, because torpedoes fired at long ranges take a good long while to reach their targets, Clark said. That means the Navy will have to puzzle out how to relay targeting updates to the Mark 48 as it travels toward the enemy ship from so far away.

David B. Larter was the naval warfare reporter for Defense News.

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