During the American Revolutionary War, Turtle was a one-person submersible. Its designer hoped its operator could approach an enemy ship and attach an explosive device.
Such early submarines needed manual propulsion and had limited underwater capabilities. Later development depended on advances in power, navigation, and air management.
Development
American inventor David Bushnell had the idea of a submersible vessel for use in lifting the British naval blockade during the American War of Independence. Bushnell may have begun studying underwater explosions while at Yale College. By early 1775, he had created a reliable method for detonating underwater explosives, a clockwork connected to a musket firing mechanism, probably a flintlock adapted for the purpose.
After the Battles of Lexington and Concord in April 1775, Bushnell began work near Old Saybrook on a small, individually manned submarine designed to attach an explosive charge to the hull of an enemy ship. He wrote to Benjamin Franklin that it would be "Constructed with Great Simplicity and upon Principles of Natural Philosophy."
Little is known about the origin, inspiration, and influences for Bushnell's invention. It seems clear that Bushnell knew of the work of Dutch inventor Cornelis Drebbel. According to Dr. Benjamin Gale, the many brass and mechanical parts of the submarine were built by New Haven inventor Isaac Doolittle, whose shop was just half a block from Yale.
Bushnell is given the overall design credit for the Turtle by Gale and others, but Doolittle was well known as an "ingenious mechanic", engraver, and metalworker. He had designed and manufactured complicated brass-wheel hall-clocks, a mahogany printing-press, brass compasses, and surveying instruments. He also owned a brass foundry where he cast bells. At the start of the American Revolution, Doolittle built a gunpowder mill with two partners in New Haven to support the war, and the Connecticut government sent him to prospect for lead.
Preparation for use
Funding was one of Bushnell's central concerns as he planned and constructed the Turtle. Colonial records concerning the Turtle are often short and cryptic, due to efforts to keep it secret from the British, and most of the records that do exist concern Bushnell's request for funds. Bushnell met with Connecticut Governor Jonathan Trumbull during 1771 seeking financial support. Trumbull also sent requests to George Washington and Thomas Jefferson. Jefferson was intrigued by the possibilities, while Washington remained skeptical of devoting funds from the Continental Army, whose funding was already being stretched.
Several setbacks plagued the design process. The mine in particular was delayed several times from its expected completion from 1771 to 1776. Piloting the Turtle, moreover, required great physical stamina and coordination. The operator would have to adjust the bilge in order to keep from sinking while providing propulsion by use of a crank, which worked a propeller on the front of the submarine, and simultaneously directing the submarine with a lever that operated a rudder at the back. The cabin also held air for only 30 minutes of use, after which the operator would have to surface and replenish the air through a ventilator. Training would be needed in order to ensure the project's success due to the complex nature of the machine.
Attack on the Eagle
At 11:00 pm on September 7, 1776, Sgt. Lee piloted the submersible toward Admiral Richard Howe's flagship HMS Eagle, then maneuvered it out to the anchorage off Governors Island. It took two hours to reach his destination, as it was hard work manipulating the hand-operated controls and foot pedals to propel the submersible. Adding to his difficulties was a fairly strong current and the darkness, which made visibility difficult.
Bushnell believed that Lee's failure was probably due to an iron plate connected to the ship's rudder hinge. Lee attempted another spot on the hull, but he was unable to stay beneath the ship and eventually abandoned the attempt.