General Electric YJ93

{{Short description|Turbojet engine}}  {{infobox aero engine |name= YJ93 |image = File:General Electric YJ93-GE-3 Turbojet, National Museum of the US Air Force, Dayton, Ohio, USA. (44702066100).jpg |caption = YJ93-GE-3 engine at the National Museum of the United States Air Force |engine_type= Turbojet engine |national_origin = United States |manufacturer= General Electric Aircraft Engines |first_run= |major_applications= North American XB-70 Valkyrie |number_built = |developed_from = |variants_with_their_own_articles = |developed_into = General Electric GE4 }}

The '''General Electric YJ93''' turbojet engine was designed as the powerplant for both the North American XB-70 Valkyrie bomber and the North American XF-108 Rapier interceptor. The YJ93 was a single-shaft axial-flow turbojet with a variable-stator compressor and a fully variable convergent/divergent exhaust nozzle. The maximum sea-level thrust was {{convert|28,800|lbf|kN|abbr=on}}.<ref name="Jenkins_Landis"/>

==Design and development== The YJ93 started life as the General Electric J79-X275, an enlarged version of the General Electric J79 turbojet with "275" meaning Mach 2.75, the engine's target operating speed.<ref name=eightdecades>{{cite book |title=Eight Decades of Progress : A Heritage of Aircraft Turbine Technology |date=1990 |publisher=GE Aircraft Engines |pages=117 |lccn=90082948}}</ref> This design evolved into the X279 when Mach 3 cruise became a requirement, and ultimately became the YJ93.<ref>Jenkins, Dennis R. and Tony R. Landis. ''Valkyrie: North American's Mach 3 Superbomber''. North Branch, Minnesota: Specialty Press, 2005. {{ISBN|1-58007-072-8}}. </ref>

thumb|right|YB-58 at Edwards AFB with GE J93 engine pod The engine used a special high-temperature JP-6 fuel. The six YJ93 engines in the XB-70 Valkyrie were capable of producing a thrust to weight ratio of 5:1 allowing for a speed of {{convert|2000|mph|km/h|abbr=on}} (approximately Mach 3) at an altitude of {{convert|70000|ft}}.<ref>[https://www.nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/Display/Article/195701/general-electric-yj93-ge-3-turbojet/ National Museum of the USAF] Retrieved: December 21, 2016</ref> The first engine went on test in September 1958 and featured advanced technology achievements such as electrolytically drilling longitudinal air cooling holes in the turbine blades.<ref name=eightdecades/>

The XF-108 interceptor was cancelled outright, and the B-70 project was re-oriented to a research project only.<ref>[http://home.att.net/~jbaugher2/b58_9.html NB-58A Testbed for General Electric J93] {{webarchive|url=https://web.archive.org/web/20080724113441/http://home.att.net/~jbaugher2/b58_9.html |date=2008-07-24}}</ref>

==Variants== Thrust given in foot-pounds (lbf) and kilonewtons (kN).

;J93-GE-1: {{convert|24800|lbf|kN|abbr=on}} with afterburner.<ref>{{cite web |title=Characteristics Summary: F-108A |url=http://www.alternatewars.com/SAC/F-108_Rapier_CS_-_2_May_1958.pdf |publisher=US Air Force |access-date=15 December 2018 |date=2 May 1958}}</ref> ;J93-GE-3: Production variant produced in small numbers for the North American XB-70 Valkyrie program. ;J93-GE-3R: Variant with thrust reverser, {{convert|27200|lbf|kN|abbr=on}} with afterburner.<ref>{{cite web |title=Characteristics Summary: F-108A |url=http://www.alternatewars.com/SAC/F-108A_Rapier_CS_-_15_December_1958.pdf |publisher=US Air Force |access-date=15 December 2018|date=15 December 1958}}</ref> ;J93-GE-3AR: Variant intended for the North American XF-108 Rapier.

==Applications== * Convair NB-58A Hustler (testbed) * North American XB-70 Valkyrie * North American XF-108 Rapier (intended)

==Specifications (J93-GE-3)== {{jetspecs |ref=Aircraft engines of the World 1966/77,<ref name=AEotW66-67>{{cite book |last=Wilkinson |first=Paul H. |title=Aircraft engines of the World 1966/77 |year=1966 |publisher=Sir Isaac Pitman & Sons Ltd. |location=London |edition=21st|page=83}}</ref> Military Turbojet/Turbofan Specifications,<ref name="turbo">{{cite web|title=Military Turbojet/Turbofan Specifications|url=http://www.jet-engine.net/miltfspec.html|website=www.jet-engine.net|access-date=31 December 2017|archive-date=2 October 2011|archive-url=https://web.archive.org/web/20111002090707/http://www.jet-engine.net/miltfspec.html|url-status=dead}}</ref> North American XB-70A Valkyrie<ref name="Jenkins_Landis">{{cite book|last1=Jenkins|first1=Dennis R.|last2=Landis|first2=Tony|title=North American XB-70A Valkyrie|date=2002|publisher=Specialty Press Publishers and Wholesalers|location=North Branch [USA]|isbn=1-58007-056-6}}</ref> |type=Turbojet with afterburner |length={{cvt|237|in}} |diameter={{cvt|52.5|in}} |weight={{cvt|5000|lb}} |compressor=11-stage axial |combustion=Annular with 36 dual fuel nozzles |turbine=Two-stage axial |fueltype=Special high-temperature JP-6 Fuel to MIL-F-25656 |oilsystem=Return oil spray system at {{cvt|60|psi}} |power= |thrust={{cvt|22000|lbf|kN}} dry; {{cvt|30000|lbf|kN}} with afterburner |compression= |aircon={{cvt|275|lb/s|kg/s}} |turbinetemp={{cvt|1149|C|F K}} |fuelcon= |specfuelcon={{cvt|0.700|tsfc}} dry; {{convert|1.800|tsfc|abbr=on}} wet |power/weight= |thrust/weight=6 }}

==See also== {{aircontent |see also=

|lists= * List of aircraft engines }}

==References== {{reflist}}

==External links== {{Commons category}}

Category:1950s turbojet engines YJ93 Category:Abandoned military aircraft engine projects of the United States