The Turtle was the world's first submarine to ever be used in warfare. It was designed and built in Connecticut in 1775 by David Bushnell for the purpose of approaching "Men of War" while submerged and attaching an explosive mine below the water line to sink the enemy ship. Governor Trumbull of the Colony of Connecticut was a friend and advisor of General Washington throughout the revolutionary period. Washington, in turn, affirmed Trumbull as a true patriot and took high stock in his advice. Trumbull wrote to Thomas Jefferson and George Washington with the recommendation of Bushnell and his "Turtle" concept. Jefferson, an inventor himself, liked the idea but Washington maintained his doubts, ultimately agreeing to provide funds to build and test the machine. Bushnell was himself a graduate of Yale with a degree in engineering while having a natural interest in nautical design concepts. As such, inspiration and critical thinking on the subject was not in short supply. This seafaring interest during the revolutionary war gave him what he needed to propose to design the world's first combat submarine. This was a "true" invention in every sense of the word, with no preexisting template to fall back on whatsoever - in itself, the Turtle was a new revolutionary design and technological model.
As one can expect, one problem after another had to be overcome. Such issues arose as how the one-man crew could breathe when submerged, how to navigate with or against the current, propulsion techniques, how to submerge/resurface, basic buoyancy and how would the operator see anything once inside the submerged Turtle especially at night. Bushnell not only had to conceive a device that never existed but he also had to design and build it himself.
Bushnell proceeded by building into the hull six smallish thick-glassed windows to provide natural lighting and considered using a candle while the vessel was submerged. Experiments with the candle proved inadequate because of the confined spaces - the candle flame would eventually consume the operator's oxygen supply. He wrote Benjamin Franklin about this dilemma and Franklin, intrigued with the problem, suggested using bioluminescent foxfire fungi found on decaying trees. During the natural decaying process the fungi would produce a bluish-green "glow" in the dark. This produced just enough illumination for the operator to read his compass and depth meter.
With internal navigation resolved, propulsion proved the next major hurdle. Sails, oars and poling were the current types of propulsion used on water so there was very little to go on in terms of powering a submarine. In the Turtle, the operator became the horsepower output and a hand crank was devised to spin two propellers, one for vertical movement and the other for forward progress. This was the first recorded use of a screw propeller on any sea-going vessel. To submerge the Turtle, Bushnell needed a process for the water to enter a bilge tank at the bottom of the vessel. Conversely, to surface he installed a hand pump to push the water out into an outside spare tank. In case of an emergency he installed up to 700 hundred pounds of lead that could be quickly released to surface the vessel.
The Turtle got its name due to it resembling a large turtle shell. It was about 8 feet long, 6 feet (1.8 m) tall, and about 3 feet (0.9 m) wide - the body construction consisting of two wooden oak shells covered with tar and reinforced with steel bands. It was water tight and had air for one person for approximately thirty minutes and could make some distance at about 3 miles an hour.
As a naval weapon, the Turtle was fitted with a limpet mine that needed to be set in place by the crewman, this accomplished via drilling into the target ship's hull and attaching the keg containing about 130/150 pounds of gunpowder. A timed fuse provided the safety needed for the Turtle to skirt away to a safe distance before ensuing explosion. The Connecticut River was used as the testing ground and David Bushnell and his brother, Ezra Bushnell, took turns as pilot and observer. The tests were deemed successful and General Washington blessed the Turtle's first mission into New York harbor. Volunteers were recruited and trained to carry out the actual mission. An Army Sergeant by the name of Ezra Lee got the now-historical assignment and, after much drilling, he attacked the HMS Eagle - the flagship of British Admiral Howe - near today's Governors Island located just south of Manhattan.
The attack itself was a failure; two scenarios offering possible solutions to the failed attempt are most often quoted. Firstly, some feel the drill could not have penetrated the copper sheet covering the hull. Copper sheeting was a common material used to combat worms. The second was that Lee could not steady the craft enough against the hull of the ship to use the drill especially due to wave action. Lee ended up releasing the keg of gun powder when spotted by British Marines and made his escape in the Turtle. A few weeks later, another attack was launched, this time in the Hudson River. Again with Lee at the controls, the Turtle ventured out but lost sight of the target ship. As the Turtle was egg-shaped with the small end down, the top portion had the glass windows positioned just slightly above the waterline so the operator could see his way to the target. Wave action washing over the Turtle and any applicable river currents proved too much for the clumsy Turtle and its 3 knots-per-hour speed.
Inevitable, the slow-moving Turtle was sunk by cannon fire in Fort Lee, New Jersey while it was being taken to its next mission. It was recovered however, but never to be used again. Bushnell wrote to Jefferson that he dismantled it before it could be discovered by the British. Bushnell went on to become Captain of Engineers in Washington's army and Lee was transferred into the new Secret Service. Bushnell moved to France in 1795 but returned to the United States once more, settling Georgia where he preceded to shortened his name to Bush. He practiced medicine for many years after and died in 1823. Upon review of his papers considering the Turtle, it was accepted that Bushnell was one of the greatest inventors of his time.
A copy of the Turtle design was built during the War of 1812 but was equally as unsuccessful against an attack of the British ship HMS Ramillies.