{{short description|Simple, bladeless radial steam turbine}} {{Redirect|Hero engine|the game engine and server technology platform|HeroEngine}} {{Use dmy dates|date=January 2021}} [[Image:Aeolipile illustration.png|thumb|An illustration of Hero's aeolipile]] An '''aeolipile''', '''aeolipyle''', or '''eolipile''', also known as a '''Hero's''' (or '''Heron's''') '''engine''', is a simple, bladeless [[Radial turbine|radial steam turbine]] which spins when the central water container is heated. [[Torque]] is produced by steam jets exiting the turbine. The [[Greeks in Egypt|Greek-Egyptian]] [[mathematician]] and [[engineer]] [[Hero of Alexandria]] described the device in the 1st century CE, and many sources give him the credit for its invention.<ref name="HeroSteamEngine"/><ref>{{cite book|title=Herons von Alexandria Druckwerke und Automatentheater|author-last=Hero|author-link=Hero of Alexandria|others=Wilhelm Schmidt (translator)|place=Leipzig|publisher=B.G. Teubner|date=1899|language =el, de|chapter-url=https://archive.org/stream/heronsvonalexandhero#page/228/mode/2up|pages=228–232|chapter=Pneumatika, Book II, Chapter XI}}</ref> However, at least one source credits [[Vitruvius]] as the first to describe this appliance in his ''[[De architectura]]'' ({{Circa|30–20 BCE}}).<ref>Kirk, William. "The geographical significance of Vitruvius’ de architectura." Scottish Geographical Magazine 69.1 (1953): 1-10.</ref>
The aeolipile is considered to be the first recorded [[steam engine]] or reaction [[steam turbine]], but it is neither a practical source of power nor a direct predecessor of the type of steam engine invented during the [[Industrial Revolution]].<ref>"This toy [Aeolipile] was not the forerunner of any real steam engine, then or later. Such devices represent technical ingenuity but not technological progress." See [[A. G. Drachmann]], ''The Classical Civilization'', pp. 55–56.</ref>
The name – derived from the [[Ancient Greek]] name Αἴολος and the [[Latin]] word ''pila'' – translates literally to {{gloss|the ball of [[Aeolus]]}}, Aeolus being the [[Greek mythology|Greek god]] of the air and wind.
Because it applies steam to perform work, an aeolipile (depicted in profile) is used as the symbol for the U.S. Navy's Boiler Technician Rate, as it was for the earlier Watertender, Boilermaker, and Boilerman ratings.
==Physics== [[Image:Herosenginesmall.jpg|thumb|A classroom model of an aeolipile]] The aeolipile usually consists of a spherical or cylindrical vessel with oppositely bent or curved [[nozzle]]s projecting outwards. It is designed to rotate on its axis. When the vessel is pressurised with steam, the gas is expelled out of the nozzles, which generates thrust due to the [[rocket engine|rocket]] principle<ref>[http://www.daviddarling.info/encyclopedia/A/aeolipile.html Aeolipile<!-- Bot generated title -->]</ref> as a consequence of the 2nd and 3rd of [[Newton's laws of motion]]. When the nozzles, pointing in different directions, produce forces along different lines of action perpendicular to the axis of the [[Bearing (mechanical)|bearings]], the thrusts combine to result in a rotational moment (mechanical [[Couple (mechanics)|couple]]), or [[torque]], causing the vessel to spin about its axis. Aerodynamic drag and frictional forces in the bearings build up quickly with increasing rotational speed ([[Revolutions per minute|rpm]]) and consume the accelerating torque, eventually cancelling it and achieving a [[steady state]] speed.
Typically, and as Hero described the device, the water is heated in a simple [[boiler]] which forms part of a stand for the rotating vessel. Where this is the case, the boiler is connected to the rotating chamber by a pair of pipes that also serve as the [[wiktionary:Pivot|pivot]]s for the chamber. Alternatively the rotating chamber may itself serve as the boiler, and this arrangement greatly simplifies the pivot/bearing arrangements, as they then do not need to pass steam. This can be seen in the illustration of a classroom model shown here.
==History== [[File:Aeolipile (from Pneumatica).jpg|thumb|right|Illustration from Hero's ''Pneumatica'']] Both Hero and Vitruvius draw on the much earlier work by [[Ctesibius]] (285–222 BCE), also known as Ktēsíbios or Tesibius, who was an inventor and mathematician in [[Alexandria]], [[Ptolemaic Kingdom|Ptolemaic Egypt]]. He wrote the first known treatises on the science of compressed air and its uses in pumps.
===Vitruvius's description=== [[Vitruvius]] (c. 80 BCE – c. 15 BCE) mentions aeolipiles by name:
{{blockquote|Aeolipilae are hollow brazen vessels, which have an opening or mouth of small size, by means of which they can be filled with water. Prior to the water being heated over the fire, but little wind is emitted. As soon, however, as the water begins to boil, a violent wind issues forth.<ref name="Vitruvius">{{cite book |last=Vitruvius |author-link=Vitruvius |title=De Architectura, book 1 |series=Ten Books on Architecture |publication-date=2008-05-17 |at=Chapter VI, paragraph 2 (pages 24–25) |url=https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Vitruvius/1*.html |access-date=9 December 2021}}</ref>}}
===Hero's description=== Hero (c. 10–70 CE) takes a more practical approach, in that he gives instructions how to make one:
{{blockquote|No. 50. The Steam-Engine.
PLACE a cauldron over a fire: a ball shall revolve on a pivot. A fire is ignited under a cauldron, A B, (fig. 50), containing water, and covered at the mouth by the lid C D; with this the bent tube E F G communicates, the extremity of the tube being fitted into a hollow ball, H K. Opposite to the extremity G place a pivot, L M, resting on the lid C D; and let the ball contain two bent pipes, communicating with it at the opposite extremities of a diameter, and bent in opposite directions, the bends being at right angles and across the lines F G, L M. As the cauldron gets hot it will be found that the steam, entering the ball through E F G, passes out through the bent tubes towards the lid, and causes the ball to revolve, as in the case of the dancing figures.<ref name="HeroSteamEngine"/>}}
==Practical usage== [[Image:aeolipile.jpg|thumb|right|A modern replica of Hero's aeolipile.]] It is not known whether the aeolipile was put to any practical use in ancient times, and if it was seen as a pragmatic device, a whimsical novelty, an object of reverence, or some other thing. A source described it as a mere [[curiosity]] for the ancient Greeks, or a "party trick".<ref>{{Cite book|title=Blazing the Trail: The Early History of Spacecraft and Rocketry|last=Gruntman|first=Mike|author-link=Mike Gruntman|publisher=American Institute of Aeronautics and Astronautics, Inc.|year=2004|isbn=156347705X|location=Reston, VA|pages=1}}</ref> Hero's drawing shows a standalone device, and was presumably intended as a "temple wonder", like many of the other devices described in ''[[Pneumatica]]''.{{clarify|date=April 2017}}<ref name = "HeroSteamEngine">{{citation | title =The Pneumatics of Hero of Alexandria |chapter=Section 50 – The Steam Engine |author=Hero |date=1851 |publisher=Taylor Walton and Maberly |location=London |bibcode=1851phal.book.....W |chapter-url=http://www.history.rochester.edu/steam/hero/section50.html |archive-url=https://web.archive.org/web/20120211223728/http://www.history.rochester.edu/steam/hero/section50.html |archive-date=2012-02-11 |translator=Bennet Woodcroft |via=University of Rochester}}</ref>
[[Vitruvius]], on the other hand, mentions use of the aeolipile for demonstrating the physical properties of the weather. He describes them as: {{blockquote|brazen æolipylæ, which clearly shew that an attentive examination of human inventions often leads to a knowledge of the general laws of nature.<ref name="Vitruvius" />}} After describing the device's construction (see above) he concludes: {{blockquote|Thus a simple experiment enables us to ascertain and determine the causes and effects of the great operations of the heavens and the winds.<ref name="Vitruvius" />}} [[File:Αιολόσφαιρα Μουσείο Κοτσανά Αρχαίας Ελληνικής Τεχνολογίας.jpg|thumb|A large reconstruction of Heron's aeolipile at [[Museum of Ancient Greek Technology|Kotsanas Museum of Ancient Greek Technology]] in [[Athens]], Greece.]] In 1543, [[Blasco de Garay]], a scientist and a captain in the Spanish navy, allegedly demonstrated before the [[Charles V, Holy Roman Emperor|Holy Roman Emperor, Charles V]] and a committee of high officials an invention he claimed could propel large ships in the absence of wind using an apparatus consisted of copper boiler and moving wheels on either side of the ship.<ref name=":0">{{Cite book|title=Innovation and Technological Diffusion: An economic history of early steam engines|last=Kitsikopoulos|first=Harry|publisher=Routledge|year=2015|isbn=9781138948112|location=Oxon|pages=5}}</ref> This account was preserved by the royal Spanish archives at [[Simancas]].<ref name=":1">{{Cite book|title=Floating Palaces of the Great Lakes: A History of Passenger Steamships on the Inland Seas|last=Stone|first=Joe|publisher=University of Michigan Press|year=2015|isbn=9780472071753|location=Ann Arbor|pages=9}}</ref> It is proposed that de Garay used Hero's aeolipile and combined it with the technology used in Roman boats and late medieval galleys.<ref name=":0" /> Here, de Garay's invention introduced an innovation where the aeolipile had practical usage, which was to generate motion to the paddlewheels, demonstrating the feasibility of steam-driven boats.<ref name=":1" /> This claim was denied by Spanish authorities.<ref name="MuseoNaval">Museo Naval, Catálogo guia del Museo Naval de Madrid, IX edición, Madrid, 1945, page 128.</ref>
==See also== {{commons category}} {{div col|colwidth=30em}} *[[Catherine wheel (firework)]] *[[Rocket engine]] *[[Segner wheel]] *[[Steam engine]] * [[Steam locomotive]] *[[Steam rocket]] *[[Tip jet]] {{div col end}}
==References== {{reflist|30em}}
==Further reading== *{{cite web |url=https://hackaday.com/2020/10/06/making-a-modern-version-of-a-steam-engine-from-antiquity/ |title=Making a Modern Version of a Steam Engine From Antiquity |first=Dan |last=Maloney |website=[[Hackaday]] |date=6 October 2020 |access-date=6 October 2020 |ref=none}} *{{cite web |url=https://www3.nd.edu/~powers/ame.20231/keyser1990.pdf |title=A New Look at Heron's "Steam Engine" |first=Paul |last=Keyser |website=[[University of Notre Dame]] |date=1 June 1992 |access-date=25 March 2023 |ref=none}}
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