Aeolipile

Aeolipile

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Aeolipile

An illustration of Hero's aeolipile

An aeolipile (also spelled aeolipyle), a rocket-like^[1] jet engine^[2] invented in the first century by Hero of Alexandria, is considered to be the first recorded steam engine or reaction steam turbine.^[3] The name?derived from the Greek words "aeolos" and "pila"?translates to "the ball of Aeolus" ; Aeolus being the Greek god of the wind.

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Features

It consists of an air-tight chamber (usually a sphere or cylinder) rotating on a bearing of some kind, with bent or curved nozzles projecting from it (tipjets), through which steam is expelled perpendicular to the bearing axis. The resulting thrust due to the rocket principle^[4] causes a torque which makes the device spin (Newton's third law).

A modern replica of Hero's aeolipile

Typically, the water is heated in a basin, which is connected to the rotating chamber by a pair of pipes that also serve as the pivots for the chamber. However, the water may also be heated in the chamber itself as shown in the illustration.

A classroom model of an aeolipile

The device was thought of as little more than a diversion during Hero's lifetime. He invented a separate machine that used air from a closed chamber, heated by an altar fire, to displace water from a sealed vessel; the water was collected and its weight, pulling on a rope, opened temple doors.^[5] Some historians have conflated the two inventions to assert that the aeolipile was used, in antiquity, for the production of useful work. This conflation appears to be incorrect.