Bushnell Turtle

History of the Bushnell Turtle

The Turtle was the first submarine in the world to be used in warfare. It was designed and built in Connecticut by David Bushnell in 1775 to approach the "Man of War" underwater and to lay explosive mines below the waterline to sink enemy ships. Colonial Connecticut Governor Trumbull was a friend and advisor to General Washington during the Revolution.

As far as Washington was concerned, it affirmed that Trumbull was a true patriot and took his advice. Trumbull wrote to Thomas Jefferson and George Washington with Bushnell's recommendation and his "turtle" concept. Jefferson, an inventor himself, liked the idea, but Washington remained skeptical and eventually agreed to grant money to build and test the machine. Bushnell is a Yale graduate with an engineering degree and a natural interest in nautical design concepts.

So there is no shortage of inspiration and critical thinking on the subject. His interest in sailing during the Revolutionary War gave him the ability to design the world's first combat submarine.

It's a "true" invention in every sense of the word, with no existing template to fall back on - Turtle itself is a new revolutionary design and technology model.

As expected, problem after problem had to be overcome. Questions about how a single crew member can breathe underwater, how to navigate with or against current, propulsion techniques, how to dive/surface, basic buoyancy and how operators can see underwater turtles, especially at night.

Not only did Bushnell have to conceive a device that never existed, but he also had to design and build it himself.

Bushnell built six small thick glass windows in the hull to allow natural light in, and considered candles when the boat was underwater. Experiments with candles proved insufficient due to the cramped room - the candle's flame eventually consumed the operator's oxygen supply. He wrote about the dilemma to Benjamin Franklin, who was intrigued by the issue, suggesting the use of bioluminescent foxfire mushrooms found on decaying trees. During natural decomposition, mushrooms produce a blue-green "glow" in the dark.

This provides the operator with enough lighting to read his compass and depth gauge.

Drive proved to be the next big hurdle as internal navigation was resolved. Sails, rudders and rods are the types of propulsion currently used on the water, so there is very little that can be done to propel a submarine. On the Turtle, the operator turned into horsepower, and a hand crank was designed to turn two propellers, one for vertical motion and the other for forward motion. This is the first record of a propeller being used on a sea-going ship. To drown the turtles, Bushnell needed a process to get water into a bilge tank at the bottom of the boat.

Instead, he installed a hand pump on the ground to push water into an external storage tank. In an emergency, he installed up to 700 pounds of lead, which could be quickly released onto the ship.

The turtle got its name because it resembles a large turtle shell. It is approximately 8 feet long, 6 feet (1.8 m) high and 3 feet (0.9 m) wide - the body structure is two wooden oak shells covered with tar and reinforced with steel strips.

It's waterproof, can be ventilated for about 30 minutes by a person, and can travel at about 3 miles per hour.

As a naval weapon, the Turtle is equipped with a limpet mine that must be installed by the crew by drilling into the hull of the target ship and attaching a barrel of approximately 130/150 lbs of gunpowder. Timed fuses provide the necessary safety net to keep the tortoise flying a safe distance before an explosion occurs. The Connecticut River was used as a proving ground, with David Bushnell and his brother Ezra Bushnell taking turns serving as pilot and observer. The test was deemed a success, and General Washington blessed the Turtles for their first mission in New York Harbor.

Volunteers are recruited and trained to perform practical tasks. An Army sergeant named Ezra Lee took on the now-historic assignment, and after several maneuvers, he attacked the HMS Eagle the flagship of British Admiral Howe near what is now Governors Island, south of Manhattan.

The attack itself is a failure; two situations are most often mentioned that provide possible solutions to the failed attempt. First of all, some people believe that the drill bit cannot penetrate the copper sheet covering the hull. Copper sheet is a common material used to control worms. The second reason was that Lee was unable to stabilize the boat sufficiently on the hull to use the drill, especially due to wave action. Lee eventually let go of the powder keg and escaped the Turtles when the British Marines found out.

A few weeks later, another attack occurred on the Hudson River. With Lee at the helm again, the Turtles ventured off without sight of the target ship.

Because the turtle is egg-shaped, with its small head facing down, the upper glazing sits just above the waterline, allowing the operator to see his path to the target. The wave action of sea turtles and all applicable river scours is too much for the clumsy sea turtles and their speed of 3 knots per hour.

While being transported to its next mission, the slow-moving turtle was inevitably sunk by artillery fire at Fort Lee, NJ. However, it was salvaged but never used again. Bushnell wrote to Jefferson that he had torn it down before the British found it. Bushnell became an engineer captain in the Washington Army, and Lee was promoted to the new Secret Service.

Bushnell emigrated to France in 1795, but returned to the United States and settled in Georgia, where he shortened his name to Bush. He then practiced medicine for many years and died in 1823.

After reviewing his treatise on tortoises, Bushnell was considered one of the greatest inventors of his time.

Copies of the

Turtle design were built during the War of 1812, but were similarly unsuccessful against the British ships HMS Ramillies.

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