Turtle

Turtles are reptiles of the order Testudines (or Chelonii) characterised by a special bony or cartilaginous shell developed from their ribs and acting as a shield. "Turtle" may refer to the order as a whole (American English) or to fresh-water and sea-dwelling testudines (British English).

The order Testudines includes both extant (living) and extinct species. The earliest known members of this group date from 157 million years ago, making turtles one of the oldest reptile groups and a more ancient group than snakes or crocodilians. Of the 327 known species alive today, some are highly endangered.

Turtles are ectotherms—their internal temperature varies according to the ambient environment, commonly called cold-blooded. However, because of their high metabolic rate, leatherback sea turtles have a body temperature that is noticeably higher than that of the surrounding water.

Turtles are classified as amniotes, along with other reptiles, birds, and mammals. Like other amniotes, turtles breathe air and do not lay eggs underwater, although many species live in or around water.

Turtle (robot)

Turtles are a class of educational robots designed originally in the late 1940s (largely under the auspices of researcher William Grey Walter) and used in computer science and mechanical engineering training. These devices are traditionally built low to the ground with a roughly hemispheric (sometimes transparent) shell and a power train capable of a very small turning radius. The robots are often equipped with sensor devices which aid in avoiding obstacles and, if the robot is sufficiently sophisticated, allow it some perception of its environment. Turtle robots are commercially available and are common projects for robotics hobbyists.

Turtle robots are closely associated with the work of Seymour Papert and the common use of the Logo programming language in computer education of the 1980s. Turtles specifically designed for use with Logo systems often come with pen mechanisms allowing the programmer to create a design on a large sheet of paper. The original Logo turtle, built by Paul Wexelblat at BBN, was named "Irving" and was demonstrated at the former Muzzey Junior High in Lexington, Massachusetts. "Irving" contained bump sensors and could give audio feedback with a bell. The development of the robotic Logo turtle led to the use of the term to describe the cursor in video screen implementations of the language and its turtle graphics package.

DSV Turtle

Turtle (DSV-3) is a 16-ton, manned deep-ocean research submersible owned by the United States Navy. It is sister to Alvin (DSV-2), and also an Alvin class Deep Submergence Vehicle. The Turtle was retired from active service in 1998. It now resides at the Mystic Aquarium in Mystic, Connecticut

The Turtle was designed to dive to 6000 feet. When DSV-2 Alvin installed a new titanium hull, the Alvin steel hull was installed in the Turtle. The Turtle depth rating was then increased to 10,000 feet. It has a hull 2 inches thick, and a hatch about 3-1/2 inches thick held in place by the pressure of the water above it (it is tapered, narrower inward). The Alvin-class DSV's were designed to replace older DSV, such as the less maneuverable Trieste-class bathyscaphes.

Alvin class DSV

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