Editing Plug nozzle (section)

==In aircraft and missiles==
[[File:Jumo 004 im Technikmuseum Hugo Junkers Dessau 2010-08-06 Detail 03.jpg|thumb|right|Sectioned Jumo 004 exhaust nozzle, showing the ''Zwiebel'' restrictive body]]
The jet-engine plug nozzle has its origins in rocketry<ref>{{Cite web |url=https://ntrs.nasa.gov/search.jsp?R=19920013861 |title=Plug nozzles: The ultimate customer driven propulsion system |first=Carl A. |last=Aukerman |date=August 1, 1991 |via=ntrs.nasa.gov |access-date=July 25, 2018 |archive-date=October 5, 2021 |archive-url=https://web.archive.org/web/20211005081854/https://ntrs.nasa.gov/search.jsp?R=19920013861 |url-status=live }}</ref> but has also been studied over the years, but not used, for supersonic cruise aircraft such as the Boeing SST,<ref>{{cite web |url=https://ntrs.nasa.gov/search.jsp?R=19900011721 |title=Exhaust Nozzles for Propulsion Systems with Emphasis on Supersonic Cruise Aircraft |date=May 1, 1990 |last=Stitt |first=Leonard E. |website=ntrs.nasa.gov |page=31 |access-date=July 25, 2018 |archive-date=October 5, 2021 |archive-url=https://web.archive.org/web/20211005081855/https://ntrs.nasa.gov/search.jsp?R=19900011721 |url-status=live }}</ref> the proposed General Electric Variable Cycle Engine, with its acoustic plug nozzle,<ref>{{Cite web |url=https://www.flightglobal.com/pdfarchive/view/1982/1982%20-%200703.html |title=Archived copy |access-date=2018-07-25 |archive-date=2018-07-26 |archive-url=https://web.archive.org/web/20180726040955/https://www.flightglobal.com/pdfarchive/view/1982/1982%20-%200703.html |url-status=dead }}</ref> and Concorde. However, it was used for the [[AGM-28 Hound Dog]] missile and the Tu-144 airliner. The plug / "external-expanding" nozzle has a central plug and a freely-expanding supersonic jet rather than a diverging cone surface to contain the internal supersonic expansion as in a delaval [[convergent-divergent nozzle]] (con-di) nozzle. The [[Pratt & Whitney J52]] aircraft engine used in the supersonic [[AGM-28 Hound Dog]] missile used a plug nozzle which performed better over the missile's flight envelope than either a convergent or a con-di nozzle.<ref>The Engines of Pratt & Whitney, Jack Connors 2010, {{ISBN|978-1-60086-711-8}}, p.276</ref> A translating center-body was used on the non-afterburning [[Kolesov RD-36-51]]A engine used for the [[Tupolev Tu-144]]D supersonic airliner. The center-body was perforated and compressed air forced into the exhaust jet through the perforations to attenuate the noise.<ref>Tupolev Tu-114' Gordon, Komissarov and Rigmant, Schiffer Publishing Ltd. 2015, {{ISBN|978-0-7643-4894-5}}, p.188</ref> 
Weight and cooling are typical concerns with aircraft plug nozzles.<ref name="Ref Pub 235">{{cite journal
 | url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19900011721_1990011721.pdf
 | title=Exhaust Nozzles for Propulsion Systems With Emphasis on Supersonic Cruise Aircraft
 | publisher=[[NASA]]
 | journal=Reference Publication 1235
 | date=May 1990
 | last=Stitt
 | first=Leonard E.
 | access-date=14 July 2012
 | archive-date=17 May 2010
 | archive-url=https://web.archive.org/web/20100517000844/http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19900011721_1990011721.pdf
 | url-status=live
 }} (42.1 Mb)</ref> A plug nozzle design evaluated at the National Gas Turbine Establishment<ref>{{Cite web |url=http://naca.central.cranfield.ac.uk/reports/arc/cp/0841.pdf |title=Archived copy |access-date=2018-07-25 |archive-date=2015-10-01 |archive-url=https://web.archive.org/web/20151001191904/http://naca.central.cranfield.ac.uk/reports/arc/cp/0841.pdf |url-status=dead }}</ref> was rejected for the Concorde engine due to the weight penalty from the required variable features and concerns about adequate plug cooling during reheat operation.<ref>A Case Study By Aerospatiale And British Aerospace On The Concorde, Rech and Leyman, AIAA Professional Study Series, p. 6-10</ref> 
Plug nozzle model tests have shown reduced noise levels compared to traditional con-di nozzles.<ref>Journal of Sound and Vibration
Volume 206, Issue 2, 18 September 1997, Pages 169–194.</ref>

Propelling nozzles for subsonic aircraft have used a center-body/bullet/cone to give the nozzle exit area required to set an axial compressor running-line correctly on its map. The first operational German turbojet engines with axial compressors, the [[Jumo 004]] and [[BMW 003]], needed a different exhaust nozzle areas for running properly at each of the operating regimes: start/idle, climb, high speed, high altitude.<ref>Jet Propulsion Progress, First edition, Neville and Silsbee, McGraw-Hill Book company, Inc. New York and London, 1948</ref> A nozzle with a fore/aft-translating "bullet" restrictive body in the center was chosen for each design. It provided area control with relatively simple actuation and matched the annular shape of the turbine exhaust.