Heron’s Aeolipile: What Is the Purpose of the World’s First Working Steam Engine?

The invention of the steam engine was credited to English engineer Thomas Savery, who patented the first commercially used steam pump in 1698. The creation of the steam engine served as the key technology in the Industrial Revolution which led to the development of semi-automated factories.

However, historical records suggest that the steam engine is not a new invention, as it was designed as early as the first century A.D.

Heron's Aeolipile

In 62 AD, the Mediterranean port city of Alexandria became a tidepool of new religions. New forms of worship sprouted in the 2.2 million-square-mile expanse as it served as the melting pot of Egyptian, Greek, and Roman influences.

To win the competition for followers, priests turned to Heron to create celestial phenomena. Also known as Mechanikos (machine man), Heron was an engineer, mathematician, and inventor who created a large collection of devices and tools, such as a water organ, a fire engine, and the first coin-operated machine.

Heron's most famous work is recorded in two books collectively known as Pneumatica, in which he describes his advanced mechanical ideas. One of the ideas presented in the Pneumatica is Heron's Engine or Aeolipile, which literally means "wind ball."

The device included a sealed caldron of water placed over a source of heat. As the water boiled, steam came out of the pipes and into the hollow sphere. The steam then escaped from bent outlet tubes on the ball, causing the call to rotate. The idea behind this design is almost identical to that of modern jet propulsion.

This early version of steam engine was very simple and is considered a "radial steam turbine" that did not have any blades. As the steam left the engine, it caused the center of the device to spin and generate torque.

Historians noted that evidence of a device called Aeolipile was already present in writing which came before Heron's time. For instance, Roman architect and engineer Vitruvius mentioned the engine in one of his works. However, what the device was or what it looked like was not mentioned, so the credit goes to Heron.

What Is the Purpose of Heron's Aeolipile?

In its most basic form, a steam engine refers to a type of engine which uses hot steam to enable it to to work. In short, the steam drives the mechanical components of the engine to move.

In the paper "A New Look at Heron's 'Steam Engine," Paul Keyser explored how the machine worked and described it as the wrong design to produce much in the way of usable power. According to him, the rotating sleeve joints either have excess leakage or excess friction, which can reduce the machine's efficiency. The sphere would not also have enough inertia to provide a smooth output for different loads. Additionally, it would spin too fast to enable simple reduction gearing to transmit the power.

Heron's Aeolipile is far from the true steam engines which were created centuries later. Instead, Keyser described it as the first demonstration of a rocket and reactive force. Heron also did not consider this device as something that can be useful for everyday application.

So, what is the purpose of the Greek Aeolipile? Unfortunately, Heron left it to speculation. Some experts believe that it was used as a novelty item to amuse and astound ancient Greeks. Others assume that it was invented as a children's toy. Beyond that, it could have been used to create miracles in temples.