Aeolipile

Fill the boiler with water, light a fire beneath, steam rises up through the tubes attached to the sphere and ultimately escapes through the bent tubes, causing the sphere to spin.

Supposedly, Hero employed this technology in a device which controlled the doors of the local temple.

The Greeks were the masters of missed opportunity.

When you are very young, the basic principles of physics are amazing.

You don't know about Newton, thermodynamics, or inertia. You are learning by experience that the universe is a place where things move in very predictable ways, but you have not been in enough classrooms yet to forget the magic of this. When you fill a bucket with toys and swing it upside down without everything spilling out, you've discovered centrifugal force.

I may be taking shots at classrooms because I'm a product of California's public education system, which is a subset of America's public education system. I cannot say anything new about why this is screwed up. But the rudiments of physics are best learned by experience. You want to learn about the transfer of direction and distance of kinetic energy, play on a seesaw. If you want to delve deeper, take the back off an analog watch and watch the gears turn. You'll learn when you take up a book to study up on your observations that a seesaw and a set of gears operate on the same principle: a gear is nothing more than a wheel made of levers. You'll learn later on that if you put a lot of large gears together in the right way, you've got an automotive transmission. Large revelations come from small ones.

Unfortunately, the ancient Greeks didn't get much into the math part of physics. They never made it past the small revelations. They invented the steam engine less than one hundred years after the birth of Christ and used it as a toy.

Aeolipile = aeoli + pila; ball of Aeolus, Greek god of wind. Aeolipile is a wind ball. Prounounced Ay-uhl-i-pile.

Hero was a high-profile mathematician and craftsman in Alexandria. He had a number of contraptions to his name that exploited rudimentary physics and which, if applied correctly, might have set the Industrial Revolution moving almost two thousand years before the Europeans did. His most famous — and frustrating — is the aeolipile.

An aeolipile is a very simple device. It consists of a boiler connected to a pivoting ball with pipes extending out, crimped and bent perpendicular. Fill the boiler with water, heat it up; the water evaporates, expanding up into the ball. The steam builds pressure at the crimps in the pipes and shoots out, spinning the ball on the pivot. For every action there is an equal and opposite reaction. Expansion of fluid into a gas builds pressure in a closed container. Provide an opening, the gas escapes with force. Direct the force accordingly, and you've got a small reaction turbine: heart of the steam engine.

One cannot describe the importance of gas expansion to our modern world. Nuclear reactors? Nothing more than multiple-phase steam engines with nuclear fission producing the heat for boiling instead of coal. We can only imagine what the world would be today if Hero had seen fit to apply the energy of shooting steam to something useful.

Building your own aeolipile

You too can create the biggest missed opportunity in all of history.

Assuming you are without the resources to melt and forge iron and procure steam-resistent fittings, you can build your own aeolipile with the following:

• A small tin can with a lid
• 2 thin brass tubes
• A length of beaded brass chain
• A rubber sheet at least as large as the mouth of the can
• A wide, flat piece of wood
• A small can of sterno
• Two wooden dowels
  • One large dowel, about ½" x 15"
  • One small dowel, about ¼" x 5"
• A small nail
• A high-wattage soldering gun
• A metal file
• Needlenose pliers
• Wire cutters
• A drill

Next, take your brass tubes. Crimp them almost shut, placing the crimp about an inch from an open end. Use your wire cutters to cut at the crimps. Use the needlenose pliers to pinch the newly cut-off opening so that there is a tiny space for steam to escape.

Now, insert the brass tubes into the holes you punched near the top of the can — open end inside the can, tight end outside. Angle the tubes so that they're tangent to the can to direct the force of the escaping steam properly. Refer to my illustration, wherein the + is the center of the can and the ==== is the brass tubing. ASCII art is good exercise for the imagination.

====
   +
   ====

Remove the lid and use it to trace a circle in your rubber sheet. Cut out the circle. Place the circle against the bottom of the lid. Replace the lid so that it's pinching rubber sheet all the way around the mouth of the can. You've just made a gasket.

Now, drill a hole in the wide, flat piece of wood near an edge into which the larger dowel will fit snugly. Now drill a hole in the side of the larger dowel near the tip into which the smaller dowel will fit snugly. Now drill a hole in the smaller dowel near the tip into which your length of brass chain will fit snugly. Thread the chain through the small dowel. Attach the remaining pieces accordingly. When you're finished, it should look like a hangman game.

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Fill the can with about half an inch of water and light the sterno. Soon the water will boil, and if you've constructed your aeolipile to direct its steam properly it will spin.

Field, Simon Quellan. "Science toys you can make with your kids."
http://www.scitoys.com/scitoys/thermo/thermo.html#heat

Author unknown. "Aeolipiles or Wind Balls."
http://www.allesoberballen.com/engels/AEOLIPILE.html

Wikipedia
http://en.wikipedia.org/wiki/Aeolipile

What is an aeolipile?

According to many sources the aeolipile is a steam engine, or a jet engine; but it has also been described as a rocket-like reaction engine.

Clearly it's a steam engine, because it's driven by steam.

And equally clearly, the aeolipile is pushed around by the reaction to emitted steam, so it's a reaction engine as well.

And because it's reacting to the steam jets, it's also a jet engine.

But what's a rocket-like jet engine?

It's a rocket.

Consider the fact that the propulsive force is created solely from the propellant that is held in a tank in the device. Consider also that the propellant is formed into a jet which pushes it around. Thus it can be seen that the aeolipile is a hot water rocket engine on a bearing.

Just putting a rocket on a bearing doesn't make it not a rocket, in the same way as putting a jet engine on a bearing doesn't make it not a jet engine. As a similar example, some experimental helicopters have used rocket tips; they're still rocket engines even though they go around in circles, with propellant fed from tanks in the body.

So if you agree that it's a jet engine, then it's also a rocket engine.

So by definition(*) the aeolipile was a rocket engine.

That means that rocket (engines) were invented first century A.D. in Alexandria, not in the 13th Century in China, as is commonly believed. (Of course rocket in the sense of a free flying vehicle or missile probably was invented in China, but that's a separate question).

So, it's a jet engine, and a steam engine and a reaction engine and a rocket engine... these things are not mutually exclusive...

Notes:

*- For the record the criteria for rocket engines are:

1. it takes the propellant from an attached tank (in an aeolipile it comes from the water tank)
2. it forms it into a jet which it uses for propulsion (in an aeolipile it comes out of nozzles and it is pushed around by the propulsive jet)
3. all propulsion comes solely from the propellant

Æ*ol"i*pile, Æ*ol"i*pyle (#), n. [L. aeolipilae; Aeolus god of the winds + pila a ball, or Gr. gate (i. e., doorway of Æolus); cf. F. éolipyle.]

An apparatus consisting chiefly of a closed vessel (as a globe or cylinder) with one or more projecting bent tubes, through which steam is made to pass from the vessel, causing it to revolve.

⇒ Such an apparatus was first described by Hero of Alexandria about 200 years b. c. It has often been called the first steam engine.

© Webster 1913.