USS Union (1842)

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USS Union (1842) was the U.S. Navy’s experimental steamer built to test a new way of powering ships with steam. It was laid down at the Norfolk Navy Yard in 1841, launched in 1842, and commissioned in early 1843 under Lt. W. W. Hunter. The ship used the Hunter Wheel, a horizontally mounted paddle-wheel drum inside the hull, with paddles that protruded through the side. A cofferdam around the wheel kept water out. Union’s early trials began with a February 1843 cruise that stopped in Washington, Boston, New York, and Philadelphia before returning to Norfolk. Although praised by Lt. Hunter and the Secretary of the Navy, the design turned out to waste energy by driving the wheels through the water-filled cofferdam.

Union joined the Home Squadron in 1844 and conducted a second round of tests into 1845. Engines were later replaced with more powerful ones, but the improvements did not fix the paddle-wheel inefficiency. She was put in ordinary (in reserve) at Norfolk in 1847. In 1848 she was sent to the Philadelphia Navy Yard and converted into a receiving ship; her machinery and paddle wheels were removed and sold. Union remained in Philadelphia as a receiving ship until sold in 1858.

Specifications: displacement 956 tons; length 184 ft 6 in; beam 33 ft 6 in; draught 11 ft 3 in. Propulsion: steam engine with side wheels; speed about 7 knots. Armament: four 68-pounder guns.