Reporter's Notebook

Gi-normous

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PORT HURON, MICH. – Half the Freedom’s combined-diesel-and-gas powerplant are its two Rolls-Royce MT-30 turbine engines, which ride deep under the waterline in a pair of enormous metal boxes. The ship’s engineering spaces are designed to be unmanned, but when the engines were powered down yesterday, Chief Gas Turbine Systems Technician (Electrical) Raymond Quezada opened up the box on the starboard turbine to show us around.

I suggested the MT-30 seemed bigger than the familiar General Electric LM 2500 turbines that power most of the Navy’s surface combatants.

“Oh man, it’s gi-normous,” he agreed. Quezada described how two sailors with whom he’d served on a destroyer came aboard the Freedom in Milwaukee to check out his new engine room, and they were blown away.

“Whenever people say to me, ‘well, on the LM 2500, it’s this,’ I have to stop them,” Quezada said. “This is nothing like the LM 2500.”

Operating together, the two MT-30s generate about 100,000 horsepower, which can combine with the output from the ship’s two Fairbanks-Morse main diesels, if so directed by a sailor at a console on the bridge. The engines give the ship’s water jets the power they need to vacuum in seawater and then blast it aft, yielding one crew nickname for the Freedom: a giant jet-ski. The ship can rise two feet out of the water at high speed.

Ticonderoga-class cruisers and Arleigh Burke-class destroyers have a set of four LM 2500s, but no propulsion diesels, to drive their traditional twin propellers. Those ships can make 30 knots on about 80,000 horsepower for cruisers and 100,000 for destroyers, but they’re much bigger — more than 9,000 tons, compared to the Freedom’s 3,000. If destroyers are Adm. Arleigh Burke’s “greyhounds of the sea,” the Freedom is the electric jackrabbit they chase around the track. 

Quezada likes the MT-30s because they’re completely self-contained, he said, and they run diagnostic tests on themselves when they start up. The downside, compared to LM 2500s, is that the Rolls-Royce engines use a lot more fuel. But the Navy understood that when it designed the ship, he said.

“Your little Hyundai gets great gas mileage at 60 or 65 miles per hour,” Quezada said, “but your Chevy Corvette or your Dodge Viper gets a lot more power. It uses more gas, but you get what you pay for.”