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What is an aeolipile?

What is an aeolipile?

An aeolipile is a mechanism that is regarded as the first steam engine or reaction steam turbine ever made, and precursor to the jet engine. It was invented at some point in the 1st century AD by an ancient Greek mathematician and engineer named Heron, who resided in the great city of Alexandria, Roman Egypt. Because of this, the aeolipile is often referred to as the "Hero engine".

Hero's aeolipile worked on exactly the same fundamentals as the later machines of the industrial revolution and many modern day electricity-generating turbines!

So how exactly does a Hero engine work? It really is quite brilliant in its simplicity.

The aeolipile consisted of a small water reservoir with a heat source located underneath it. Two copper tubes extended upwards from this water tank to act as the pivot for a rotating sphere. This sphere had two oppositely bent or "L-shaped" nozzles projecting from it.

The heat source would heat the water causing steam to rise through the copper tubes and into the mounted sphere. The steam would then "escape" through the L-shaped nozzles at high speed generating thrust (concurrent to Newton’s 2nd and 3rd laws of motion). This thrust would cause the sphere to spin on its axis. As the speed of the spinning sphere increased, so too did the aerodynamic drag of the sphere and friction in the axis bearings. Eventually these factors would cancel with the sphere's accelerating torque and it would achieve a steady state speed.

(An illustration of Heron's aeolipile -

Heron of Alexandria was also responsible for the invention of other innovative devices including the first wind powered machine in history, and even the first vending machine!

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