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The '''Lockheed SR-71''' "'''Blackbird'''" is a retired [[Range (aeronautics)|long-range]], high-altitude, [[Mach number|Mach]]&nbsp;3+ [[military strategy|strategic]] [[reconnaissance aircraft]] developed and manufactured by the American aerospace company [[Lockheed Corporation]].{{refn|This was prior to Lockheed's merger with [[Martin Marietta]] in 1995, after which it was known as the modern day [[Lockheed Martin]].|group=N}} The SR-71 has several nicknames, including "[[Common blackbird|Blackbird]]" and "[[Trimeresurus flavoviridis|Habu]]".<ref name="auto2">{{harvp|Crickmore|1997|p=64}}</ref>
 
The SR-71 was developed as a [[black project]] from the [[Lockheed A-12]] reconnaissance aircraft during the 1960s by Lockheed's [[Skunk Works]] division. American aerospace engineer [[Kelly Johnson (engineer)|Clarence "Kelly" Johnson]] was responsible for many of the aircraft's innovative concepts.<ref>{{cite web |title=Creating the Blackbird |url=https://www.lockheedmartin.com/en-us/news/features/history/blackbird.html |access-date=March 14, 2010 |work=[[Lockheed Martin]]}}</ref> The shape of the SR-71 was based on that of the Lockheed A-12, which was one of the first aircraft to be designed with a reduced [[radar cross-section]] in mind. Initially, a [[strategic bomber|bomber]] variant of the A-12 was requested by [[Curtis LeMay]], before the program was focused solely on reconnaissance. The SR-71 was longer and heavier than the A-12, allowing it to hold more fuel as well as a two-seat cockpit. The SR-71's existence was revealed to the public in July 1964; it entered service in the [[United States Air Force]] (USAF) in January 1966.<ref>{{cite web |last=Merlin |first=Peter W. |title=Blackbird Facts |url=https://www.nasa.gov/pdf/736495main_Blackbird_FAQ.pdf |publisherarchive-url=https://web.archive.org/web/20140311221447/https://www.nasa.gov/pdf/736495main_Blackbird_FAQ.pdf |archive-date=11 March 2014 |access-date=23 June 2024 |website=[[NASA]] |page=3}}</ref> In 1989, the USAF retired the SR-71, largely for political reasons;<ref>{{Cite news |last=Richelson |first=Jeffrey |title=Air Force Tries to Shoot Down Its Own Spy |url=https://www.latimes.com/archives/la-xpm-1989-04-09-op-1582-story.html |date=April 9, 1989 |access-date=2023-12-28 |work=Los Angeles Times}}</ref> several were briefly reactivated during the 1990s before their second retirement in 1998. [[NASA]] was the final operator of the Blackbird, using it as a research platform; it was retired again in 1999.<ref>{{cite web |last=Gibbs |first=Yvonne |date=March 1, 2014 |title=NASA Armstrong Fact Sheet: SR-71 Blackbird |url=https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-030-DFRC.html |access-date=July 6, 2022 |work=[[NASA]] |archive-date=23 November 2016 |archive-url=https://web.archive.org/web/20161123054447/https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-030-DFRC.html |url-status=dead }}</ref>
 
Mission equipment for the plane's [[aerial reconnaissance]] role included [[signals intelligence]] sensors, [[side looking airborne radar]], and a camera.<ref name="outran">{{cite web|url=https://nationalinterest.org/blog/the-sr-71-blackbird-the-super-spy-plane-outran-missiles-18142|work=[[The National Interest]]|first=Sebastien|last=Roblin |date=21 October 2016 |access-date=6 July 2022 |title=The SR-71 Blackbird: The Super Spy Plane That Outran Missiles}}</ref> During missions, the SR-71 operated at high speeds and altitudes (Mach 3.2 and {{cvt|85000|ft|m|sigfig=2|sp=us|disp=semicolon}}), allowing it to outrace or entirely avoid threats.<ref name="outran" /> If a [[surface-to-air missile]] launch was [[Missile approach warning system|detected]], the standard evasive action was simply to accelerate and outpace the missile.<ref name="SR71 Blackbird 2006">"SR-71 Blackbird." PBS documentary, Aired: 15 November 2006.</ref> On average, each SR-71 could fly once per week due to the extended turnaround required after mission recovery. A total of 32 aircraft were built; 12 were lost in accidents with none lost to enemy action.<ref name="Landis_p98-101">{{harvp|Landis|Jenkins|2004|pp=98,100-101}}</ref><ref name="Pace_p126-7" /><!-- Wording to prevent back & forth 'were none'/'was none' changes. -->
 
Since its retirement, the SR-71's role has been taken up by a combination of [[reconnaissance satellite]]s and [[unmanned aerial vehicle]]s (UAVs); a proposed UAV successor, the [[Lockheed Martin SR-72|SR-72]], is under development by Lockheed Martin, and scheduled to fly in 2025.<ref name="US pushes hard">{{cite web|url=https://www.btimesonline.com/articles/105181/20181123/u-s-pushes-hard-build-sr-72-hypersonic-fighter.htm|title=U.S. Pushes Hard To Build SR-72 Hypersonic Fighter|first=Artie |last=Villasanta|publisher=Business Times|date=November 23, 2018}}</ref> {{As of|2024}}, the SR-71 still holds the world record, which it set in 1976, as the [[Flight airspeed record|fastest air-breathingairbreathing manned aircraft]], previously held by the closely related [[Lockheed YF-12]].<ref name="landis_jenkins_p78">{{harvp|Landis|Jenkins|2004|p=78}}</ref><ref name="Pace_p159">{{harvp|Pace|2004|p=159}}</ref><ref name="FAI_records" />
 
==Development==
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The SR-71 designation is a continuation of the [[1924 United States Army Air Service aircraft designation system|pre-1962 bomber series]]; the last aircraft built using the series was the [[XB-70 Valkyrie]]. However, a bomber variant of the Blackbird was briefly given the B-71 designator, which was retained when the type was changed to SR-71.<ref>{{cite web|url=http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=2699 |title=Lockheed B-71 (SR-71) |date=29 October 2009 |publisher=National Museum of the United States Air Force |access-date=2 October 2013 |url-status=dead |archive-url=https://web.archive.org/web/20131004214346/http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=2699 |archive-date=4 October 2013 }}</ref>
 
During the later stages of its testing, the B-70 was proposed for a reconnaissance/strike role, with an "RS-70" designation. When the A-12's performance potential was clearly found to be much greater, the USAF ordered a variant of the A-12 in December 1962,<ref name="Landis_p56">{{harvp|Landis|Jenkins|2004|pp=56-57}}</ref> which was originally named R-12 by Lockheed.{{refn|See the opening fly page in {{harvp|Crickmore|2000}}, which contains a copy of the original R-12 labeled plan view drawing of the vehicle.|group=N}} This USAF version was longer and heavier than the original A-12 because it had a longer fuselage to hold more fuel. The R-12 also had a larger two-seat cockpit, and reshaped fuselage [[Chine (aeronautics)|chines]]. Reconnaissance equipment included [[signals intelligence]] sensors, a [[side-looking airborne radar]], and a photo camera.<ref name="Landis_p56"/> The CIA's A-12 was a better photo-reconnaissance platform than the USAF's R-12,: since the A-12 flew somewhat higher and faster, and with only one pilot, it had room to carry a superior camera<ref name="futile"/> and more instruments.<ref>{{harvp|McIninch|1971|p=29}}</ref> The A-12 flew [[covert mission]]s while the SR-71 flew overt missions; the latter had USAF markings and pilots carried [[Geneva Conventions Identification Card]]s.<ref name="iwm20211103">{{Cite AV media |url=https://www.youtube.com/watch?v=Tn9U6hAlf14 |title=SR-71 Blackbird - Cold War icon |date=2021-11-03 |type=YouTube |publisher=Imperial War Museums}}</ref>
 
During the [[1964 United States presidential election|1964 campaign]], Republican presidential nominee [[Barry Goldwater]] repeatedly criticized President [[Lyndon B. Johnson]] and his administration for falling behind the [[Soviet Union]] in developing new weapons. Johnson decided to counter this criticism by revealing the existence of the YF-12A USAF interceptor, which also served as cover for the still-secret A-12<ref name="oxcartstory">{{harvp|McIninch|1971|pp=14-15}}</ref> and the USAF reconnaissance model since July 1964. USAF Chief of Staff General [[Curtis LeMay]] preferred the SR (Strategic Reconnaissance) designation and wanted the RS-71 to be named SR-71. Before the July speech, LeMay lobbied to modify Johnson's speech to read "SR-71" instead of "RS-71". The media transcript given to the press at the time still had the earlier RS-71 designation in places, creating the story that the president had misread the aircraft's designation.<ref name="Merlin_p4-5">{{harvp|Merlin |2005, |pp. 4–5.=4-5}}</ref>{{refn|{{harvp|Crickmore|2000}}, original R-12 labeled plan view drawing|group=N}} To conceal the A-12's existence, Johnson referred only to the A-11, while revealing the existence of a high speed, high altitude reconnaissance aircraft.<ref>{{harvp|McIninch|1971}}</ref>
 
In 1968, Secretary of Defense [[Robert McNamara]] canceled the F-12 interceptor program. The specialized tooling used to manufacture both the YF-12 and the SR-71 was also ordered destroyed.<ref name=Landis_p47>{{harvp|Landis|Jenkins|2004|p=47}}</ref> Production of the SR-71 totaled 32 aircraft with 29 SR-71As, two SR-71Bs, and the single SR-71C.<ref name=Merlin_p6>{{harvp|Merlin |2005, |p. =6.}}</ref>
 
==Design==
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[[File:Lockheed SR-71A Blackbird, National Museum of the United States Air Force, Wright-Patterson Air Force Base, near Dayton, Ohio, USA, cockpit, forward view.png|thumb|Forward cockpit|alt=The flight instrumentation of an SR-71's forward cockpit]]
 
The SR-71 was designed for flight at over [[Mach number|Mach]]&nbsp;3 with a two-men flight crew of two in tandem cockpits,. with theThe pilot in the forward cockpit operates the aircraft, and the reconnaissance systems officer operatingin the surveillancerear systems and equipment fromoperates the rearsurveillance cockpit,systems andwhile directing navigation onnavigating the mission flight path.<ref name=crown>[https://fas.org/irp/program/collect/sr-71.htm "Senior Crown SR-71."] ''[[Federation of American Scientists]],'' 7 September 2010. Retrieved: 17 October 2012. [https://web.archive.org/web/20150417003154/https://fas.org/irp/program/collect/sr-71.htm Archived] on 17 April 2015.</ref><ref name="SR-71 Revealed">{{harvp|Graham|1996}}</ref> The SR-71 was designed to minimize its radar cross-section, an early attempt at stealth design.<ref>{{harvp|Crickmore|2009|pp=30-31}}</ref> Finished aircraft were painted ain dark blue,an almost black-like dark blue, to increase the emission of internal heat and to act as [[aircraft camouflage|camouflage]] against the night sky. The dark color led to the aircraft's nickname "Blackbird".
 
While the SR-71 carried [[Radar jamming and deception|radar countermeasure]]s to evade interception efforts, its greatest protection was its combination of high altitude and very high speed, which made it almost invulnerable at the time. Along with its low radar cross-section, these qualities gave a very short time for an enemy [[surface-to-air missile]] (SAM) site to acquire and track the aircraft on radar. By the time the SAM site could track the SR-71, it was often too late to launch a SAM, and the SR-71 would be out of range before the SAM could catch up to it. If the SAM site could track the SR-71 and fire a SAM in time, the SAM would expend nearly all of the [[delta-v]] of its boost and sustainer phases just reaching the SR-71's altitude; at this point, out of thrust, it could do little more than follow its ballistic arc. Merely accelerating would typically be enough for an SR-71 to evade a SAM;<ref name="SR71 Blackbird 2006"/> changes by the pilots in the SR-71's speed, altitude, and heading were also often enough to spoil any radar lock on the plane by SAM sites or enemy fighters.<ref name="SR-71 Revealed">{{harvp|Graham|1996}}</ref> At sustained speeds of more than Mach 3.2, the plane was faster than the Soviet Union's fastest interceptor, the [[Mikoyan-Gurevich MiG-25]],{{refn|The [[MiG-25|Foxbat]]s could sustain speeds of Mach 2.83, but they also had an emergency option to reach Mach 3.2 if they were willing to replace their engines afterwards.<ref name=GlobalAircraftMiG-25 />|group=N}} which also could not reach the SR-71's altitude.<ref name=GlobalAircraftMiG-25>[http://www.globalaircraft.org/planes/mig-25_foxbat.pl "MiG-25 Foxbat."] ''globalaircraft.org''. Retrieved: 31 May 2011. [https://web.archive.org/web/20141223100252/http://www.globalaircraft.org/planes/mig-25_foxbat.pl Archived] in 2014.</ref> During its service life, no SR-71 was ever shot down.<ref name="Landis_p98-101"/>
 
===Airframe, canopy, and landing gear===
On most aircraft, the use of [[titanium]] was limited by the costs involved; it was generally used only in components exposed to the highest temperatures, such as exhaust fairings and the leading edges of wings. On the SR-71, titanium was used for 85% of the structure, with much of the rest being [[polymer]] [[composite material]]s.<ref>{{harvp|Merlin, Peter W. [https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090007797.pdf "Design and Development of the Blackbird: Challenges and Lessons Learned"]. American Institute of Aeronautics and Astronautics|2009}}</ref> To control costs, Lockheed used a more easily worked titanium alloy which softened at a lower temperature.{{refn|Lockheed obtained the metal from the [[Soviet Union]] during the [[Cold War]], under many guises to prevent the Soviet government from discovering for what it was to be used.|group=N}} The challenges posed led Lockheed to develop new fabrication methods, which have since been used in the manufacture of other aircraft. Lockheed found that washing welded titanium requires [[distilled water]], as the chlorine present in tap water is [[corrosion|corrosive]]; [[cadmium]]-plated tools could not be used, as they also caused corrosion.<ref>{{harvp|Rich|Janos|1994|p=213-214}}</ref> Metallurgical contamination was another problem; at one point, 80% of the delivered titanium for manufacture was rejected on these grounds.<ref>{{harvp|Rich|Janos|1994|p=203}}</ref><ref>{{harvp|McIninch|1971|p=5}}</ref>
 
[[File:1 - Seattle.jpg|thumb|right|upright=1.35|A [[Lockheed M-21]] with a [[Lockheed D-21|D-21]] drone on display at Seattle's Museum of Flight|alt= A [[Lockheed M-21]] with [[Lockheed D-21|D-21]] drone on top]]
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The high temperatures generated in flight required special design and operating techniques. Major sections of the skin of the inboard wings were corrugated, not smooth. Aerodynamicists initially opposed the concept, disparagingly referring to the aircraft as a Mach 3 variant of the 1920s-era [[Ford Trimotor]], which was known for its corrugated aluminum skin.<ref name="johnson_bio"/> But high heat would have caused a smooth skin to split or curl, whereas the corrugated skin could expand vertically and horizontally and had increased longitudinal strength.
 
Fuselage panels were manufactured to fit only loosely with the aircraft on the ground. Proper alignment was achieved as the airframe heated up, with [[thermal expansion]] of several inches.<ref>{{harvp|Graham, |1996, |p. =47.}}</ref> Because of this, and the lack of a fuel-sealing system that could handle the airframe's expansion at extreme temperatures, the aircraft leaked [[JP-7]] fuel on the ground prior to takeoff,<ref name="Graham, 1996, p. 160">{{harvp|Graham, |1996, |p. =160.}}</ref> annoying ground crews.{{r|iwm20211103}}
 
The outer windscreen of the cockpit was made of [[quartz]] and was [[ultrasonic welding|fused ultrasonically]] to the titanium frame.<ref>{{cite journal |last1=Burrows |first1=William E. |title=The Real X-Jet |journal=Air & Space Magazine |date=1 March 1999 |url=https://www.airspacemag.com/military-aviation/the-real-x-jet-12377380/ |access-date=16 January 2018}}</ref> The temperature of the exterior of the windscreen reached {{convert|600|°F|°C|abbr=on}} during a mission.<ref>{{harvp|Graham, |1996, |p. =41.}}</ref> Cooling was carried out by cycling fuel behind the titanium surfaces in the chines. On landing, the canopy temperature was more than {{convert|300|°C|°F|abbr=on|order=flip}}.<ref name="johnson_bio" />
 
Some SR-71s had red lines painted on the upper surface of the wing to show "no step" areas which included the trailing edge and the thin, fragile skin where the inner wing blended into the fuselage. This portion of the skin was only supported by widely spaced structural ribs.<ref>{{cite web |url=http://www.dutchops.com/AC_Data/Lockheed/Lockheed_SR71_BlackBird.htm |title=Lockheed SR-71 "Blackbird" - Air Power Provided |website=Dutchops.com |access-date=26 May 2014 |archive-date=12 September 2019 |archive-url=https://web.archive.org/web/20190912045122/http://www.dutchops.com/AC_Data/Lockheed/Lockheed_SR71_BlackBird.htm |url-status=dead }}</ref>
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[[File:Sr71 1.jpg|thumb|[[Contrail|Water vapor]] is condensed by the low-pressure vortices generated by the chines outboard of each engine inlet.]]
 
The second operational aircraft<ref name="cia.gov">{{cite web|url=https://www.cia.gov/news-information/featured-story-archive/2015-featured-story-archive/oxcart-vs-blackbird.html|archive-url=https://web.archive.org/web/20151208074002/https://www.cia.gov/news-information/featured-story-archive/2015-featured-story-archive/oxcart-vs-blackbird.html|url-status=dead|archive-date=8 December 2015|title=OXCART vs Blackbird: Do You Know the Difference? |website=Cia.gov}}</ref> designed around a [[stealth aircraft]] shape and materials, following the [[Lockheed A-12]],<ref name="cia.gov"/> the SR-71 had several features designed to reduce its [[radar]] signature. The SR-71 had a radar cross-section (RCS) around {{cvt|10|sqm|sqft|order=flip}}.<ref>{{harvp|Graham, |1996, |p. =75.}}</ref> Drawing on early studies in radar [[stealth technology]], which indicated that a shape with flattened, tapering sides would reflect most energy away from a radar beam's place of origin, engineers added [[Chine (aeronautics)|chines]] and canted the vertical control surfaces inward. Special [[radar-absorbing material]]s were incorporated into [[serration|sawtooth-shaped]] sections of the aircraft's skin. [[Cesium]]-based fuel additives were used to somewhat reduce the visibility of exhaust plumes to radar, although exhaust streams remained quite apparent. Johnson later conceded that Soviet radar technology advanced faster than the stealth technology employed against it.<ref>Hott, Bartholomew and George E. Pollock [https://web.archive.org/web/20030216054101/http://web.ics.purdue.edu/~gpollock/The%20Advent%2C%20Evolution%2C%20and%20New%20Horizons%20of%20United%20States%20Stealth%20Aircraft.htm "The Advent, Evolution, and New Horizons of United States Stealth Aircraft."] ''archive.is''. Retrieved: 7 February 2014.</ref>
 
The SR-71 featured chines, a pair of sharp edges leading aft from either side of the nose along the fuselage. These were not a feature on the early A-3 design; Frank Rodgers, a doctor at the Scientific Engineering Institute, a CIA [[front organization]], discovered that a cross-section of a sphere had a greatly reduced radar reflection, and adapted a cylindrical-shaped fuselage by stretching out the sides of the fuselage.<ref>Suhler 2009, p. 100.</ref> After the advisory panel provisionally selected Convair's FISH design over the A-3 on the basis of RCS, Lockheed adopted chines for its A-4 through A-6 designs.<ref>Suhler 2009, ch. 10.</ref>
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[[File:Inlet shock waves at Mach 2.jpg|thumb|left|[[Schlieren]] flow visualization at [[unstart]] of axisymmetric inlet at Mach 2]]
In the early years of operation, the analog computers would not always keep up with rapidly changing flight environmental inputs. If internal pressures became too great and the spike was incorrectly positioned, the shock wave would suddenly blow out the front of the inlet, called an "inlet [[unstart]]". During unstarts, afterburner extinctions were common. The remaining engine's asymmetrical thrust would cause the aircraft to yaw violently to one side. [[Stability Augmentation System|SAS]], autopilot, and manual control inputs would fight the yawing, but often the extreme off-angle would reduce airflow in the opposite engine and stimulate "sympathetic stalls". This generated a rapid counter-yawing, often coupled with loud "banging" noises, and a rough ride during which crews' helmets would sometimes strike their cockpit canopies.<ref>{{harvp|Crickmore|1997|pp=42-43}}</ref> One response to a single unstart was unstarting both inlets to prevent yawing, then restarting them both.<ref name=landis_jenkins_p97>{{harvp|Landis|Jenkins|2004|p=97}}</ref> After wind tunnel testing and computer modeling by NASA Dryden test center,<ref>{{cite web |url=https://www.nasa.gov/centers/dryden/about/Organizations/Technology/Facts/TF-2004-17-DFRC.html |title=NASA Dryden Technology Facts – YF-12 Flight Research Program |publisher=NASA |location=US |year=2004 |access-date=9 March 2019 |archive-date=12 September 2019 |archive-url=https://web.archive.org/web/20190912045121/https://www.nasa.gov/centers/dryden/about/Organizations/Technology/Facts/TF-2004-17-DFRC.html |url-status=dead }}</ref> Lockheed installed an electronic control to detect unstart conditions and perform this reset action without pilot intervention.<ref>{{harvp|Rich|Janos|1994|p=221}}</ref> During troubleshooting of the unstart issue, NASA also discovered the vortices from the nose chines were entering the engine and interfering with engine efficiency. NASA developed a computer to control the engine bypass doors which countered this issue and improved efficiency. Beginning in 1980, the analog inlet control system was replaced by a digital system, Digital Automatic Flight and Inlet Control System (DAFICS),<ref>{{Cite web |title=SR-71 Online - SR-71 Flight Manual: Section appendix, Page A-2 |url=https://www.sr-71.org/blackbird/manual/appendix/a-2.php |access-date=2023-08-21 |website=www.sr-71.org}}</ref> which reduced unstart instances.<ref name=landis_jenkins_p83>{{harvp|Landis|Jenkins|2004|p=83}}</ref>
 
===Engines===
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[[File:AG330 start cart.JPG|thumb|A preserved AG330 start cart]]
 
The SR-71 was powered by two Pratt & Whitney J58 (company designation JT11D-20) [[Axial compressor|axial-flow]] [[turbojet]] engines. The J58 was a considerable innovation of the era, capable of producing a static thrust of {{cvt|32500|lbf|kN}}.<ref name="Dryden">Kloesel, Kurt J., Nalin A. Ratnayake and Casie M. Clark. [https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110013567.pdf "A Technology Pathway for Airbreathing, Combined-Cycle, Horizontal Space Launch Through SR-71 Based Trajectory Modeling."] ''NASA: Dryden Flight Research Center''. Retrieved: 7 September 2011.</ref><ref>{{cite web |url=http://www.nasa.gov/centers/armstrong/news/FactSheets/FS-030-DFRC.html |title=NASA Armstrong Fact Sheet: SR-71 Blackbird |first=Yvonne |publisher=NASA |last=Gibbs |date=12 August 2015 |access-date=29 May 2017 |archive-date=12 September 2019 |archive-url=https://web.archive.org/web/20190912045121/https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-030-DFRC.html |url-status=dead }}</ref> The engine was most efficient around Mach&nbsp;3.2,<ref>[http://yarchive.net/air/sr71.html "SR-71."] ''yarchive.net''. Retrieved: 14 March 2010.</ref> the Blackbird's typical [[cruising speed]]. At take-off, the afterburner provided 26% of the thrust. This proportion increased progressively with speed until the afterburner provided all the thrust at about Mach 3.<ref name="Dryden"/>
 
Air was initially compressed (and heated) by the inlet spike and subsequent converging duct between the center body and inlet cowl. The shock waves generated slowed the air to subsonic speeds relative to the engine. The air then entered the engine compressor. Some of this compressor flow (20% at cruise) was removed after the fourth compressor stage and went straight to the afterburner through six bypass tubes. Air passing through the turbojet was compressed further by the remaining five compressor stages and then fuel was added in the combustion chamber. After passing through the turbine, the exhaust, together with the compressor [[bleed air]], entered the afterburner.<ref>{{cite web|url=https://www.sr-71.org/blackbird/manual/1/1-20.php|title=SR-71 Online – SR-71 Flight Manual: Section 1, Page 1-20|website=Sr-71.org}}</ref>
 
At around Mach&nbsp;3, the temperature rise from the intake compression, added to the engine compressor temperature rise, reduced the allowable fuel flow because the turbine temperature limit did not change. The rotating machinery produced less power, but still enough to run at 100% RPM, thus keeping the airflow through the intake constant. The rotating machinery had become a drag item<ref>"Jet Propulsion for Aerospace Applications" second edition, Hesse and Mumford, Pitman Publishing Corporation, Library of Congress Catalog Card Number: 64-18757, p375</ref> and the engine thrust at high speeds came from the afterburner temperature rise.<ref>"F-12 Series Aircraft Propulsion System Performance and Development" David Campbell, J. Aircraft Vol. 11, No. 11, November 1974</ref> Maximum flight speed was limited by the temperature of the air entering the engine compressor, which was not certified for temperatures above {{cvt|800|F|C|-1}}.<ref>''SR-71 Revealed'' Richard H. Graham Col USAF (Retd) {{ISBNharvp|Graham|1996|978-0-7603-0122-7}}, p. =51.}}</ref>
 
Originally, the Blackbird's J58 engines were started with the assistance of two [[Buick Wildcat]] V8 [[internal combustion engine]]s, externally mounted on a vehicle referred to as an AG330 "start cart". The start cart was positioned underneath the J58 and the two Buick engines powered a single, vertical [[drive shaft]] connecting to the J58 engine and spinning it to above 3,200 RPM, at which point the turbojet could self-sustain. Once the first J58 engine was started, the cart was repositioned to start the aircraft's other J58 engine. Later start carts used [[Chevrolet Big-Block engine|Chevrolet big-block]] V8 engines. Eventually, a quieter, pneumatic start system was developed for use at main operating bases. The V8 start carts remained at diversion landing sites not equipped with the pneumatic system.<ref>{{harvp|Landis|Jenkins|2004|pp=96-96}}</ref><ref>{{cite web |url=https://www.sr-71.org/blackbird/startercart.php |title=Starter Cart |website=SR-71 Online |location=US |year=2010 |access-date=21 July 2018}}</ref>
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[[File:Boeing KC-135Q refueling SR-71.JPEG|thumb|alt= KC-135 and SR-71 during an "in-flight" re-fueling|An SR-71 refueling from a KC-135Q Stratotanker during a flight in 1983]]
 
Several exotic fuels were investigated for the Blackbird. Development began on a [[coal slurryJP-7]] power plant, but Johnson determined that the coal particles damaged important engine components.<ref name="johnson_bio"/> Researchfuel was conducted on a [[liquid hydrogen]] powerplant, but its low density meant that fuel tanks would be too largeused.<ref name="johnson_bio"/> In practice, the Blackbird would burn somewhat conventional [[JP-7]], whichIt was difficult to ignite. To start the engines, [[triethylborane]] (TEB), which [[pyrophoricity|ignites on contact with air]], was injected to produce temperatures high enough to ignite the JP-7. The TEB produced a characteristic green flame, which could often be seen during engine ignition.<ref name="Shul"/> A chemical ignition system was also required as there was no fuel available as a heat sink for cooling electrical ignition components. The fuel had to be used for cooling the pilot and aircraft electronics.<ref>J58/SR-71 Propulsion Integration Or The Great Adventure Into The Technical Unknown, William Brown, Pratt & Whitney Aircraft Group, attachment to CIA-RDP90B00170R000100050008-1</ref>
 
On a typical mission, the SR-71 took off with only a partial fuel load to reduce stress on the brakes and tires during takeoff and also ensure it could successfully take off should one engine fail.<ref name=">{{harvp|Graham, |1996, |p. 160"=46}}</ref> Within 20 seconds the aircraft traveled {{convert|4500|ft}}, reached {{convert|240|mph}}, and lifted off. It reached {{convert|20000|ft}} of altitude in less than two minutes, and the typical {{convert|80000|ft}} [[cruising altitude]] in another 17 minutes, having used one third of its fuel.{{r|iwm20211103}} It is a common misconception that the planes refueledrefuelled shortly after takeoff because the jet fuel tanks, which formed the outer skin of the aircraft, leaked on the ground. TheIt leakingwas ofnot fuelpossible to prevent leaks when the aircraft skin was causedcold byand the tanks only sealed when the skin heated up as the aircraft speed increased. The failureability of sealantthe duesealant to theprevent highleaks heatwas andcompromised by the expansion duringand contraction of the skin with each flight.<ref>{{cite web |last1=Boudreaux |first1=Stormy |title=The SR-71 Experience |url=https://www.youtube.com/watch?v=J5qrMTtSUV8&t=2129s |website=YouTube |publisher=Air Zoo |access-date=17 September 2023}}</ref> However, the amount of fuel that leaked, measured as drops per minute on the ground from specific locations, was not enough to make refuelingrefuelling necessary; the planes refueledrefuelled because the maximum speedsspeed of the aircraft werewas only possible with aerial refuelingrefuelling.<ref>{{cite book harvp|last1=Graham |first1=Richard H. |title=SR-71: The Complete Illustrated History of the Blackbird |date=2013 |publisher=MBI Publishing |pagep=110}}</ref>
 
The SR-71 also required [[Aerial refueling|in-flight refueling]] to replenish fuel during long-duration missions. Supersonic flights generally lasted no more than 90 minutes before the pilot had to find a tanker.<ref>Marshall, Elliot, The Blackbird's Wake, Air and Space, October/November 1990, p. 35.</ref>
 
Specialized [[Boeing KC-135 Stratotanker|KC-135Q]] tankers were required to refuel the SR-71. The KC-135Q had a modified high-speed boom, which would allow refueling of the Blackbird at nearly the tanker's maximum airspeed with minimum [[Wing flutter|flutter]]. The tanker also had special fuel systems for moving [[JP-4 (fuel)|JP-4]] (for the KC-135Q itself) and JP-7 (for the SR-71) between different tanks.<ref>{{harvp|Graham, |1996, |pp. =38–39.}}</ref> As an aid to the pilot when refueling, the cockpit was fitted with a [[peripheral vision horizon display]]. This unusual instrument projected a barely visible [[artificial horizon]] line across the top of the entire instrument panel, which gave the pilot [[subliminal stimuli|subliminal]] cues on aircraft attitude.<ref>{{harvp|Crickmore|2004|p=233}}</ref>
 
===Astro-inertial navigation system{{Anchor|Astro-Inertial Navigation System|Astro-inertial navigation system}}===
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==Operational history==
===Main era===
The first flight of an SR-71 took place on 22 December 1964, at USAF [[Plant 42]] in [[Palmdale, California]], piloted by Bob Gilliland.<ref>{{Cite web|url=https://www.kesq.com/news/first-man-to-fly-the-world-s-fastest-aircraft-dies-in-rancho-mirage/1092463937 |title=First man to fly the world's fastest aircraft dies in Rancho Mirage |first=Jesus |last=Reyes |date=6 July 2019 |website=KESQ |access-date=6 July 2019 |archive-url=https://web.archive.org/web/20190706041642/https://www.kesq.com/news/first-man-to-fly-the-world-s-fastest-aircraft-dies-in-rancho-mirage/1092463937 |archive-date=6 July 2019 |url-status=dead}}</ref><ref>{{harvp|Crickmore|1997|pp=56-58}}.</ref> The SR-71 reached a top speed of Mach 3.4 during flight testing,<ref>{{cite web |last= Graham |first=Richard |title=SR-71 Pilot Interview Richard Graham, Veteran Tales interview at Frontiers of Flight Museum (at 1:02:55) |url=https://www.youtube.com/watch?v=CeBu6mRDaro#t=3775 |work=YouTube |date=6 August 2013 |publisher=Erik Johnston |access-date=29 August 2013 |ref=none}}</ref><ref>{{cite web |title=Col. Richard Graham (USAF, Ret.) |url=http://www.habu.org/graham/graham-bio.html |publisher=The Online Blackbird Museum |website=Habu.org |access-date=16 January 2016}}</ref> with pilot Major [[Brian Shul]] reporting a speed in excess of Mach 3.5 on an operational sortie while evading a missile over Libya.<ref name="Shul M3.5">{{cite book |last=Shul |first=Brian |title=The Untouchables |year=1994 |publisher=Mach One |isbn=0929823125 |page=173}}</ref> The first SR-71 to enter service was delivered to the [[9th Reconnaissance Wing#Beale Air Force Base|4200th (later, 9th) Strategic Reconnaissance Wing]] at [[Beale Air Force Base]], California, in January 1966.<ref>{{harvp|Crickmore|1997|p=59}}</ref>
 
SR-71s first arrived at the 9th SRW's Operating Location (OL-8) at [[Kadena Air Base]], Okinawa, Japan on 8 March 1968.<ref name="auto1">{{harvp|Crickmore|1997|pp=62-64}}</ref> These deployments were code-named "Glowing Heat", while the program as a whole was code-named "Senior Crown". Reconnaissance missions over North Vietnam were code-named "Black Shield" and then renamed "Giant Scale" in late 1968.<ref>{{cite web |url=https://www.cia.gov/library/readingroom/docs/CIA-RDP79B01709A001900060005-2.pdf|archive-url=https://web.archive.org/web/20170123150906/https://www.cia.gov/library/readingroom/docs/CIA-RDP79B01709A001900060005-2.pdf|url-status=dead|archive-date=23 January 2017|title=Memorandum for the Chairman, Sanitization and Decontrol Working Group Black Shield Photography|publisher=Central Intelligence Agency|date=19 November 1968|access-date=16 July 2020}}</ref> On 21 March 1968, Major (later General) [[Jerome F. O'Malley]] and Major Edward D. Payne flew the first operational SR-71 [[sortie]] in SR-71 serial number 61-7976 from Kadena AFB, Okinawa.<ref name="auto1"/> During its career, this aircraft (976) accumulated 2,981 flying hours and flew 942 total sorties (more than any other SR-71), including 257 operational missions, from Beale AFB; Palmdale, California; Kadena Air Base, Okinawa, Japan; and [[RAF Mildenhall]], UK. The aircraft was flown to the [[National Museum of the United States Air Force]] near [[Dayton, Ohio]] in March 1990.
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While deployed at Okinawa, the SR-71s and their aircrew members gained the nickname [[Trimeresurus flavoviridis|Habu]] (as did the A-12s preceding them) after a [[Viperidae|pit viper]] indigenous to Japan, which the Okinawans thought the plane resembled.<ref name="auto2"/>
 
Operational highlights for the entire Blackbird family (YF-12, A-12, and SR-71) as of about 1990 included:<ref name=">{{harvp|Graham"|1996}}</ref>
*3,551 mission sorties flown
*17,300 total sorties flown
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The other route was known as the ''Baltic Express''. It started from Mildenhall and went through [[Jutland]] and the [[Danish straits]] before going out over the [[Baltic Sea]].<ref name=Skuddhold /> At the time, the [[USSR]] controlled the airspace from the [[Deutsche Demokratische Republik|DDR]] and to the [[Gulf of Finland]], with [[Finnish neutrality|both Finland]] and [[Swedish neutrality#The Cold War|Sweden pursuing neutrality]] in the Cold War. This meant that [[NATO]] aircraft entering the Baltic Sea had to fly through a narrow corridor of international airspace between [[Skåne County|Scania]] and [[Western Pomerania]], which was monitored by both the [[Swedish Air Force|Swedish]] and [[Soviet Air Forces]]. Starting a counter-clockwise 30 minute loop, the Blackbirds would then [[reconnoitre]] along the Soviet Union's coastal border, before slowing down to Mach 2.54 to make a left turn south of [[Åland]], and then follow the Swedish coast back towards Denmark. If the SR-71s attempted the turn at Mach 3, they could end up violating Swedish airspace, and the Swedes would [[Ground-controlled interception|direct]] [[Saab 37 Viggen|Viggens]] to intercept the offending aircraft.<ref name=Skuddhold /><ref name=AGCViggen />
 
The combination of a monitored entry point and a fixed route allowed the Swedes and the Soviets a chance to [[Scrambling (military)|scramble]] interceptors.<ref name=Skuddhold /> Swedish radar stations would observe the [[15th Air Army#After 1945|15th Air Army]] dispatch [[Su-15]]s from [[Latvian Soviet Socialist Republic|Latvia]], and [[MiG-21]]s and [[MiG-23]]s from [[Estonian Soviet Socialist Republic|Estonia]], although only the Sukhois would have even a slim chance of successfully intercepting the American aircraft.<ref name=AGCViggen /> The greater Soviet threat came from the MiG-25s [[16th Guards Fighter Aviation Division|stationed]] at [[Eberswalde#Transport|Finow-Eberswalde]] in the DDR. The Swedes noted that the Soviets usually would send a single [[MiG-25|MiG-25 "Foxbat"]] from Finow to intercept the SR-71 on their way back out of the Baltic Sea. With the Blackbird flying at 22 km, the Foxbat would regularly close to an altitude of 19 km, precisely 3 km behind the SR-71, before disengaging. The Swedes interpreted this regularity as a sign that the MiG-25 had successfully simulated a shoot-down.<ref name=Skuddhold /><ref name=AGCViggen >{{cite news |last1=Leone |first1=Dario |title=VIGGEN Vs BLACKBIRD: HOW SWEDISH AIR FORCE JA-37 FIGHTER PILOTS WERE ABLE TO ACHIEVE RADAR LOCK ON THE LEGENDARY SR-71 MACH 3 SPY PLANE |work=The Aviation Geek Club |date=2018-01-09 |access-date=2023-10-09 |archive-date=2019-01-10 |archive-url=https://web.archive.org/web/20190110152553/https://theaviationgeekclub.com/viggen-vs-blackbird-swedish-air-force-ja-37-fighter-pilots-able-achieve-radar-lock-legendary-sr-71-mach-3-spy-plane/ |url=https://theaviationgeekclub.com/viggen-vs-blackbird-swedish-air-force-ja-37-fighter-pilots-able-achieve-radar-lock-legendary-sr-71-mach-3-spy-plane/ |url-status=live |quote=Almost every time the SR-71 was about to leave the Baltic, a lone MiG-25 Foxbat belonging to the 787th IAP at Finow-Eberwalde in [East Germany] was scrambled. […] Arriving at its exit point, the “Baltic Express” was flying at about 22km and the lone MiG would reach about 19km in a left turn before rolling out and always completing its stern attack 3km behind its target. We were always impressed by this precision; it was always 22km and 3 km behind the SR-71. [this would seem to suggest that these were the parameters necessary for its weapons system to effect a successful intercept if the order to fire was ever given.]}}</ref><ref name=rbth2012>{{cite news |last1= Simha |first1= Rakesh Krishnan |title= Foxhound vs Blackbird: How the MiGs reclaimed the skies |work= [[Russia Beyond the Headlines]] |publisher= [[Rossiyskaya Gazeta]] |date=2012-09-03 |access-date=2015-05-30 |archive-date=20162019-0108-2709 |archive-url= https://web.archive.todayorg/20160127030158web/http20190809232332/https://inwww.rbth.com/articles/2012/09/03/foxhound_vs_blackbird_how_the_migs_reclaimed_the_skies_17363.html |url= httphttps://inwww.rbth.com/articles/2012/09/03/foxhound_vs_blackbird_how_the_migs_reclaimed_the_skies_17363.html |url-status= deadlive |quote=Swedish air defence [...] radar screens [...] could see the much older but faster MiG-25 screaming in towards the Blackbird. Shortly after the MiG-31s had harried the SR-71 in the Arctic area, a lone MiG-25 Foxbat stationed at Finow-Eberswalde in the former GDR would intercept it over the Baltic. The Swedes observed the SR-71 would always fly at 72,000 ft and the MiG-25 would reach 63,000 ft before completing its stern attack 2.9 km behind the Blackbird. “We were always impressed by this precision, it was always 63,000 ft and 2.9 km behind the SR-71," a retired Swedish Air Force flight controller told Crickmore.}}<!--page 2 only clickable, not linkable or archivable--></ref>
 
The Swedes themselves would typically assert their neutrality by dispatching [[Saab 37 Viggen]]s from [[Scania Wing|Ängelholm]], [[Bråvalla Wing|Norrköping]] or [[Blekinge Wing|Ronneby]]. Limited by a top speed of Mach 2.1 and a [[Ceiling (aeronautics)|service ceiling]] of 18 km, the Viggen pilots would line up for a frontal attack, and rely on their [[state-of-the-art]] [[avionics]] in order to climb at the right time and attain a [[missile lock]] on the SR-71.<ref name=Skuddhold /><ref name=AGCViggen /> Precise timing and target illumination would be maintained with target location data [[Ground-controlled interception|supplied]] to the Viggen's [[fire-control computer]] from [[Fire-control radar|ground-based radars]],<ref name=FlyghistoriskRevy >{{cite book |editor-last1=Edlund |editor-first1=Ulf |editor-last2=Kampf |editor-first2=Hans |year=2009 |title=System 37 Viggen |series=Flyghistorisk Revy |volume=Specialnr 2009 |url= |language=SV |location=[[Stockholm]] |publisher=[[:sv:Svensk Flyghistorisk Förening|Svensk Flyghistorisk Förening]] |issn=0345-3413}}</ref> with the most common site for the [[Missile lock-on|lock-on]] being the thin stretch of international airspace between [[Öland]] and [[Gotland]].<ref name=Mach14 >{{cite magazine |author=<!--Staff writer(s); no by-line.--> |title=Mach 14 |url= |magazine=Mach |language=SV |location=[[Sweden]] |publisher= |year=1983 |volume=4 |issue=3 |page=5 |issn=0280-8498}} </ref><ref name=Mach25 >{{cite magazine |author=<!--Staff writer(s); no by-line.--> |title=Mach 25 |url= |magazine=Mach |language=SV |location=[[Sweden]] |publisher= |year=1986 |volume=7 |issue=2 |pages=28–29 |issn=0280-8498}} </ref><ref>Darwal 2004, pp. 151–156.</ref> Out of 322 recorded Baltic Express sorties between 1977 and 1988, the Swedish Air Force claims that they succeeded in attaining missile lock on the SR-71 in 51 of them.<ref name=Skuddhold >{{cite news |last1=Bonafede |first1=Håkon |title=På skuddhold av SR-71 Blackbird |trans-title=At weapons range of the SR-71 |work=[[Vi Menn]] |date=2018-05-10 |access-date=2018-05-12 |archive-date=2018-05-10 |archive-url=https://web.archive.org/web/20180510102459/http://www.side3.no/historie/pa-skuddhold-av-sr-71-blackbird/3423484769.html |url=http://www.side3.no/historie/pa-skuddhold-av-sr-71-blackbird/3423484769.html |url-status=dead |language=NB |location=Norway |via=[[:nb:Side3]] |quote=To vanlige "melkeruter" ble fløyet ukentlig [...] Den andre som ble kalt for "Baltic Express" dekket marinebasene og militærinstallasjonene til DDR og de baltiske landene. På grunn av det trange farvannet, bød ruten på utfordringer med å holde seg utenfor territorialgrensene, og flygerne fulgte nesten alltid den samme identiske ruten. [...] SR-71 kom alltid inn over radiofyret "Codan" 80 km sør for København på kurs rett østover.|trans-quote=Two common "[[milk run]]s" were flown weekly [...] The second, which was called [the] "Baltic Express" covered the Navy bases and military installations of the DDR and the Baltic countries. Because of the cramped waters, the route presented challenges as to keeping outside the territorial borders, and the pilots almost always followed the same identical route. [...] SR-71 always came in over the radio beacon "Codan" 80 km south of Copenhagen[,] heading east.}}</ref><ref name=NTSEFlygplan >{{cite news |author=<!-- Not stated --> |title=TV: Kärnvapensäkra bunkern styrde flygplanen |trans-title=TV: Aircraft controlled from nuclear weapon secured bunker |work=Kundservice |date=2017-05-02 |access-date=2017-10-07 |archive-date=2017-05-02 |archive-url=https://web.archive.org/web/20170502185029/http://www.nt.se/nyheter/ostergotland/tv-karnvapensakra-bunkern-styrde-flygplanen-om4626725.aspx |url=http://www.nt.se/nyheter/ostergotland/tv-karnvapensakra-bunkern-styrde-flygplanen-om4626725.aspx |url-status= |language=SV |location=Sweden |via= |quote=Look at time 5:57}}</ref> However, with a combined closing speed of Mach 5, the Swedes were reliant on the Blackbird not changing course.<ref name=Skuddhold /><ref name=AGCViggen />
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===Initial retirement===
One widely conventional view, and probably the best-known view, of the reasons for the SR-71's retirement in 1989—a view that the Air Force itself offered to the Congress—was that besides being very expensive, the SR-71 had become redundant anyway, among other reconnaissance methods that were ever-evolving. However, another view held by various officers and legislators is that the SR-71 program was terminated owing to [[United States Department of Defense|Pentagon]] politics, and not because the aircraft had become obsolete, irrelevant, too hard to maintain, or unsustainably expensive. Graham, a former 1st-SRS and 9th-SRW commander, presented in 1996 what he viewed as a factual summary, not an opinion, of how the SR-71 provided some intelligence capabilities that none of its alternatives (such as satellites, U-2s, and UAVs) were providing in the 1990s (when the SR-71 was retired and then re-retired from Air Force reconnaissance duty).<ref name="SR-71 Revealed"/>{{rpharvp|Graham|1996|pp=205–217}}</ref> The chief question for opinion, beyond that point, was only how crucial, or disposable, those unique advantages properly were.
 
Graham noted that in the 1970s and early 1980s, SR-71 squadron and wing commanders were often promoted into higher positions as general officers within the USAF structure and the Pentagon. (In order to be selected into the SR-71 program in the first place, a pilot or navigator (RSO) had to be a top-quality USAF officer, so continuing career progression for members of this elite group was not surprising.) These generals were adept at communicating the value of the SR-71 to a USAF command staff and a Congress who often lacked a basic understanding of how the SR-71 worked and what it did. However, by the mid-1980s, these SR-71 generals all had retired, and a new generation of USAF generals mostly wanted to cut the program's budget and spend its funding on different priorities, such as the new [[B-2 Spirit]] [[strategic bomber]] program. Such generals had an interest in believing, and persuading the services and the Congress, that the SR-71 had become either entirely or almost entirely redundant to satellites, U-2s, incipient UAV programs, and an alleged top-secret successor already under development.<ref name="SR-71 Revealed">{{harvp|Graham|1996}}</ref> Graham said that the last-mentioned one was only a sales pitch, not a fact, at the time in the 1990s.<!--Graham 1996 states this clearly: there was no secret replacement that had even started development yet (in the 1985-1995 decade), let alone being close to finished. Have to find the page number.{{rp|000}}-->
 
The USAF may have seen the SR-71 as a bargaining chip to ensure the survival of other priorities. Also, the SR-71 program's "product", which was operational and strategic intelligence, was not seen by these generals as being very valuable to the USAF. The primary consumers of this intelligence were the CIA, NSA, and DIA. A general misunderstanding of the nature of aerial reconnaissance and a lack of knowledge about the SR-71 in particular (due to its secretive development and operations) was used by detractors to discredit the aircraft, with the assurance given that a replacement was under development.<ref name="SR-71 Revealed">{{harvp|Graham|1996}}</ref> [[Dick Cheney]] told the Senate Appropriations Committee that the SR-71 cost $85,000 per hour to operate.<ref>Marshall, Eliot, "The Blackbird's Wake", Air & Space, October/November 1990, p. 35.</ref> Opponents estimated the aircraft's support cost at $400 to $700&nbsp;million per year, though the cost was actually closer to $300&nbsp;million.<ref name="SR-71 Revealed">{{harvp|Graham|1996}}</ref>
 
The SR-71, while much more capable than the Lockheed U-2 in terms of range, speed, and survivability, suffered the lack of a [[data link]], which the U-2 had been upgraded to carry. This meant that much of the SR-71's imagery and radar data could not be used in real time, but had to wait until the aircraft returned to base. This lack of immediate real-time capability was used as one of the justifications to close down the program. The counterargument was that the longer the SR-71 was not upgraded as aggressively as it ought to have been, the more people could say that it was obsolescent, which was in their interest as champions of other programs (a self-fulfilling bias). Attempts to add a datalink to the SR-71 were stymied early on by the same factions in the Pentagon and Congress who were already set on the program's demise, even in the early 1980s. These same factions also forced expensive sensor upgrades to the SR-71, which did little to increase its mission capabilities, but could be used as justification for complaining about the cost of the program.<ref name="SR-71 Revealed">{{harvp|Graham|1996}}</ref>
 
In 1988, Congress was convinced to allocate $160,000 to keep six SR-71s and a trainer model in flyable storage that could become flightworthy within 60 days. However, the USAF refused to spend the money.<ref name="SR-71 Revealed"/>{{rpharvp|Graham|1996|p=204}}</ref> While the SR-71 survived attempts to retire it in 1988, partly due to the unmatched ability to provide high-quality coverage of the [[Kola Peninsula]] for the [[United States Navy|US Navy]],<ref>{{harvp|Crickmore|1997|pp=84-85}}</ref><ref name="SR-71 Revealed"/>{{rpharvp|Graham|1996|p=194–195}}</ref> the decision to retire the SR-71 from active duty came in 1989, with the last missions flown in October that year.<ref>{{harvp|Crickmore|1997|p=81}}</ref> Four months after the plane's retirement, General [[Norman Schwarzkopf Jr.]], was told that the expedited reconnaissance, which the SR-71 could have provided, was unavailable during [[Operation Desert Storm]].<ref name="Remak">Remak and Ventolo 2001, {{page needed|date=August 2014}}</ref>
 
The SR-71 program's main operational capabilities came to a close at the end of fiscal year 1989 (October 1989). The 1st Strategic Reconnaissance Squadron (1 SRS) kept its pilots and aircraft operational and active, and flew some operational reconnaissance missions through the end of 1989 and into 1990, due to uncertainty over the timing of the final termination of funding for the program. The squadron finally closed in mid-1990, and the aircraft were distributed to static display locations, with a number kept in reserve storage.<ref name="SR-71 Revealed">{{cite book harvp|last=Graham |first=Richard |date=7 July 1996 |title=SR-71 Revealed: The Inside Story |url=https://archive.org/details/sr71revealedinsi00colr |publisher=Zenith Press |isbn=978-0760301227}}</ref>
 
===Reactivation===
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Due to unease over political situations in the Middle East and [[North Korea]], the U.S. Congress re-examined the SR-71 beginning in 1993.<ref name="Remak"/> Rear Admiral [[Thomas F. Hall]] addressed the question of why the SR-71 was retired, saying it was under "the belief that, given the time delay associated with mounting a mission, conducting a reconnaissance, retrieving the data, processing it, and getting it out to a field commander, that you had a problem in timelines that was not going to meet the tactical requirements on the modern battlefield. And the determination was that if one could take advantage of technology and develop a system that could get that data back real time... that would be able to meet the unique requirements of the tactical commander." Hall also stated they were "looking at alternative means of doing [the job of the SR-71]."<ref name="Senate">"Department of Defense Authorization for Appropriations for Fiscal Year 1994 and The Future Years." ''United States Senate'', May–June 1993.</ref>
 
Macke told the committee that they were "flying U-2s, [[Boeing RC-135|RC-135s]], [and] other strategic and tactical assets" to collect information in some areas.<ref name="Senate"/> Senator [[Robert Byrd]] and other senators complained that the "better than" successor to the SR-71 had yet to be developed at the cost of the "good enough" serviceable aircraft. They maintained that, in a time of constrained military budgets, designing, building, and testing an aircraft with the same capabilities as the SR-71 would be impossible.<ref name="Graham">{{harvp|Graham |1996}}</ref>
 
Congress's disappointment with the lack of a suitable replacement for the Blackbird was cited concerning whether to continue funding imaging sensors on the U-2. Congressional conferees stated the "experience with the SR-71 serves as a reminder of the pitfalls of failing to keep existing systems up-to-date and capable in the hope of acquiring other capabilities."<ref name=">{{harvp|Graham"|1996}}</ref> It was agreed to add $100&nbsp;million to the budget to return three SR-71s to service, but it was emphasized that this "would not prejudice support for long-endurance [[Unmanned aerial vehicle|UAVs]]" [such as the [[Global Hawk]]]. The funding was later cut to $72.5&nbsp;million.<ref name=">{{harvp|Graham"|1996}}</ref> The Skunk Works was able to return the aircraft to service under budget at $72&nbsp;million.<ref name="Jenkins">Jenkins 2001</ref>
 
Retired USAF Colonel Jay Murphy was made the Program Manager for Lockheed's reactivation plans. Retired USAF Colonels Don Emmons and Barry MacKean were put under government contract to remake the plane's logistic and support structure. Still-active USAF pilots and Reconnaissance Systems Officers (RSOs) who had worked with the aircraft were asked to volunteer to fly the reactivated planes. The aircraft was under the command and control of the [[9th Reconnaissance Wing]] at Beale Air Force Base and flew out of a renovated hangar at [[Edwards Air Force Base]]. Modifications were made to provide a data-link with "near real-time" transmission of the Advanced Synthetic Aperture Radar's imagery to sites on the ground.<ref name=">{{harvp|Graham"|1996}}</ref>
 
===Final retirement===
The reactivation met much resistance: the USAF had not budgeted for the aircraft, and UAV developers worried that their programs would suffer if money was shifted to support the SR-71s. Also, with the allocation requiring yearly reaffirmation by Congress, long-term planning for the SR-71 was difficult.<ref name=">{{harvp|Graham"|1996}}</ref> In 1996, the USAF claimed that specific funding had not been authorized, and moved to ground the program. Congress reauthorized the funds, but, in October 1997, President [[Bill Clinton]] attempted to use the [[line-item veto]] to cancel the $39&nbsp;million (~${{Format price|{{Inflation|index=US-GDP|value=39000000|start_year=1997}}}} in {{Inflation/year|US-GDP}}) allocated for the SR-71. In June 1998, the [[Supreme Court of the United States|U.S. Supreme Court]] ruled that the [[Clinton v. City of New York|line-item veto was unconstitutional]]. All this left the SR-71's status uncertain until September 1998, when the USAF called for the funds to be redistributed; the USAF permanently retired it in 1998.
 
[[NASA]] operated the two last airworthy Blackbirds until 1999.<ref>[http://www.nasa.gov/centers/dryden/news/FactSheets/FS-030-DFRC.html "NASA/DFRC SR-71 Blackbird."] {{Webarchive|url=https://web.archive.org/web/20151225025336/http://www.nasa.gov/centers/dryden/news/FactSheets/FS-030-DFRC.html |date=25 December 2015 }} ''NASA''. Retrieved: 16 August 2007.</ref> All other Blackbirds have been moved to museums except for the two SR-71s and a few [[Lockheed D-21|D-21]] drones retained by the NASA [[Dryden Flight Research Center]] (later renamed the [[Armstrong Flight Research Center]]).<ref name="Jenkins"/>
 
===Timeline===
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These four speed records were accepted by the [[National Aeronautic Association]] (NAA), the recognized body for aviation records in the United States.<ref>National Aeronautic Association</ref> Additionally, ''Air & Space/Smithsonian'' reported that the USAF clocked the SR-71 at one point in its flight reaching {{convert|2242.48|mph|km/h}}.<ref>Marshall, Elliot, The Blackbird's Wake, Air & Space, October/November 1990, p. 31.</ref> After the Los Angeles–Washington flight, on 6 March 1990, Senator [[John Glenn]] addressed the [[United States Senate]], chastising the [[United States Department of Defense|Department of Defense]] for not using the SR-71 to its full potential:
 
{{Blockquote|Mr. President, the termination of the SR-71 was a grave mistake and could place our nation at a serious disadvantage in the event of a future crisis. Yesterday's historic transcontinental flight was a sad memorial to our short-sighted policy in strategic aerial reconnaissance.<ref name="Inside Story">{{cite bookharvp|first=Richard H. |last=Graham|title=SR-71 Revealed : The Untold Story|url=https://books.google.com/books?id=6svmtOFa1JIC|publisher=Zenith Imprint|isbn=978-1-61060-751-3|year=1996}}</ref>}}
 
===Successor===
{{update-section|date=April 2024}}
{{Main|Lockheed Martin SR-72}}
Speculation existed regarding a replacement for the SR-71, including a rumored aircraft codenamed [[Aurora (aircraft)|Aurora]]. The limitations of [[reconnaissance satellite]]s, which take up to 24 hours to arrive in the proper orbit to photograph a particular target, make them slower to respond to demand than reconnaissance planes. The fly-over orbit of spy satellites may also be predicted and can allow assets to be hidden when the satellite passes, a drawback not shared by aircraft. Thus, there are doubts that the US has abandoned the concept of spy planes to complement reconnaissance satellites.<ref>Siuru, William D. and John D. Busick. ''Future Flight: The Next Generation of Aircraft Technology''. Blue Ridge Summit, Pennsylvania: TAB Books, 1994. {{ISBN|0-8306-7415-2}}.</ref> [[Unmanned aerial vehicle]]s (UAVs) are also used for aerial reconnaissance in the 21st century, being able to overfly hostile territory without putting human pilots at risk, as well as being smaller and harder to detect than manned aircraft.
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* '''SR-71A''' was the main production variant.
* '''SR-71B''' was a trainer variant.<ref>{{harvp|Landis|Jenkins|2004|pp=56-58}}</ref>
* '''SR-71C''' was a hybrid trainer<ref name="Only one">{{cite web|url=https://www.avgeekery.com/there-can-be-only-one-the-saga-of-the-only-sr-71c-ever-built/ |title=There Can Be Only One: The Saga of the Only SR-71C Ever Built |first=Bill |last=Walton |work=avgeekery.com |location=US |access-date=2021-05-16 |date=2017-05-17}}</ref> aircraft composed of the rear fuselage of the first YF-12A (S/N 60-6934) and the forward fuselage from an SR-71 static test unit. The YF-12 had been wrecked in a 1966 landing accident. It has been reported as that this Blackbird was seemingly not quite straight and had a yaw at supersonic speeds.<ref>{{harvp|Landis|Jenkins|2004|p=62,75}}</ref> However, this was caused by a mis-aligned pitot tube reporting a 4° yaw that was not actually present. It was soon corrected and then flew normally.<ref name="Only one"/><ref>{{cite web |url=https://www.thesr71blackbird.com/Aircraft/Blackbird-Aircraft/sr-71c-blackbird-17981-2001 |title=SR-71C Blackbird #17981 / #2001 |website=The SR-71 Blackbird |access-date=2023-01-24}}</ref> It was nicknamed "The Bastard".<ref name=Merlin_p4>{{harvp|Merlin |2005, |p. =4.}}</ref><ref>{{harvp|Pace|2004|pp=109-110}}</ref>
 
==Operators==
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:(Forward Operating Locations at Eielson AFB, Alaska; Griffis AFB, New York; Seymour-Johnson AFB, North Carolina; Diego Garcia and Bodo, Norway 1973–1990)
 
'''[[National Aeronautics and Space Administration]]''' (NASA)<ref>[http://www.nasa.gov/centers/armstrong/news/FactSheets/FS-030-DFRC.html Fact Sheet: SR-71 Blackbird] {{Webarchive|url=https://web.archive.org/web/20190912045121/https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-030-DFRC.html |date=12 September 2019 }}. NASA Armstrong Flight Research Center. Retrieved 28 April 2015.</ref>
*[[Dryden Flight Research Center]] – Edwards AFB, California 1991–1999
 
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| time =1h12m40s
| publisher =[[San Diego Air & Space Museum]]
}}</ref><ref>{{harvp|Graham |2013}}</ref>
|-
! scope="row" | 61-7953
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|-
! scope="row" | 61-7974
| SR-71A|| Lost, 21 April 1989 after compressor failure caused catastrophic left engine failure. Remains of aircraft recovered then on 24 Dec 1989 buried at sea in the [[Mariana trenchTrench]].<ref>{{cite web | url=https://www.planehistoria.com/sr-71-ichi-ban/? |title=SR-71 "Ichi-Ban" – Buried in the Deepest Ocean on Earth |first=Nathan |last=Cluett |work=Plane Historia |location=US |date=September 29, 2022 |access-date=October 19, 2023}}</ref>
|-
! scope="row" | 61-7975
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|max speed kts=1910
|max speed note=at {{cvt|80000|ft}}
|max speed mach=3.3{{refn|Maximum speed limit was Mach 3.2, but could be raised to Mach 3.3 if the engine compressor inlet temperature did not exceed {{convert|801|°F|°C|abbr=on}}.<ref>{{harvp|Graham |2002, |pp. =93, 223.}}</ref>|group=N}}
|cruise speed kts=
|cruise speed note=
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{{Refbegin}}
* {{Cite news |last=Ruane |first=Michael E. |date=March 7, 1990 |title=A bittersweet, and fancy, flight |volume=321 |pages=[https://www.newspapers.com/article/the-philadelphia-inquirer-a-bittersweet/130222946/ 1-A], [https://www.newspapers.com/article/the-philadelphia-inquirer-this-blackbir/130223067/ 4-A] |work=[[The Philadelphia Inquirer]] |issue=66 |via=[[Newspapers.com]]}}
* {{cite journal |last=Crickmore |date=January 2009 |first=Paul F. |title=Blackbirds in the Cold War |journal=[[Air International]] |pages=30-3830–38 |publisher=Key Publishing |location=Stamford, UK}}
* {{cite journal |last=Crickmore |date=1997 |first=Paul F. |title=Lockheed's Blackbirds – A-12, YF-12 and SR-71A |journal=[[Wings of Fame (magazine)|Wings of Fame]] |volume=8 |pages=30-9330–93 |publisher=Aerospace Publishing |location=London}}
* {{Cite book |last=Crickmore |first=Paul F. |url=https://archive.org/details/lockheedsr71secr0000cric |title=Lockheed SR-71: The Secret Missions Exposed |publisher=Osprey |year=2000 |isbn=978-1841760988 |edition=Rev. |location=Oxford |url-access=registration}}
* Donald, David, ed. "Lockheed's Blackbirds: A-12, YF-12 and SR-71". ''Black Jets''. [[AIRtime]], 2003. {{ISBN|1-880588-67-6}}.
* Goodall, James. ''Lockheed's SR-71 "Blackbird" Family''. Hinckley, UK: Aerofax/Midland Publishing, 2003. {{ISBN|1-85780-138-5}}.
* {{Cite book |last=Graham, |first=Richard H. [https://books.google.com/books?id|title=ZHkAJAq-2HQC&pg=PA223 ''SR-71 Blackbird: Stories, Tales, and Legends''.] North|date=2002 Branch,|publisher=Voyageur Minnesota:Press [[Zenith Imprint]], 2002. {{ISBN|isbn=0-7603-1142-0}}.
* {{Cite book |last=Graham |first=Richard H. |url=https://archive.org/details/sr71revealedinsi00colr |title=SR-71 Revealed: The Inside Story |publisher=Motorbooks |year=1996 |isbn=978-0760301227 |location=Osceola, WI |oclc=34319406 |url-access=registration}}
* {{Cite book |last=Graham, |first=Richard H. [https://books.google.com/books?id|title=WVGkm9COxFIC ''SR-71: The Complete Illustrated History of the Blackbird, The World's Highest, Fastest Plane''] |date=2013. {{ISBN|publisher=MBI Publishing Company |isbn=978-0760343272}}.
* Jenkins, Dennis R. ''Lockheed Secret Projects: Inside the Skunk Works''. St. Paul, Minnesota: [[MBI Publishing Company]], 2001. {{ISBN|978-0-7603-0914-8}}.
* Johnson, C.L. ''Kelly: More Than My Share of it All''. Washington, DC: [[Smithsonian Books]], 1985. {{ISBN|0-87474-491-1}}.
* {{Cite book |last1=Landis |first1=Tony R. |url=https://archive.org/details/lockheedblackbir0000jenk |title=Lockheed Blackbirds |last2=Jenkins |first2=Dennis R. |publisher=Specialty Press |year=2004 |isbn=978-1580070867 |edition=Rev. |location=North Branch, MN |oclc=60250245 |url-access=registration}}
* {{Cite journal |last=McIninch |first=Thomas P. |title=The Oxcart Story |journal=[[Studies in Intelligence]] |publisher=Center for the Study of Intelligence |volume=15 |issue=1 |pages=1-341–34 |date=1971 |access-date=23 March 2024 |url=https://www.cia.gov/resources/csi/static/The-Oxcart-Story.pdf |format=PDF |archive-url=https://web.archive.org/web/20240324012512/https://www.cia.gov/resources/csi/static/The-Oxcart-Story.pdf |archive-date=24 March 2024}}
* {{Cite book |last=Merlin, |first=Peter W. ''|title=From Archangel to Senior Crown: Design and Development of the Blackbird''., |location=Reston, Virginia:VA |publisher=[[American Institute of Aeronautics and Astronautics]] (AIAA), |year=2008. {{ISBN|isbn=978-1-56347-933-5 |editor-last=Allen |editor-first=Ned |series=Library of Flight |oclc=190761298}}.
* {{Cite journal |last=Merlin, |first=Peter W. "|title=The Truth is Out There... SR-71 Serials and Designations". ''|journal=[[Air Enthusiast]]'', No. |volume=118, |date=July/August 2005. |publication-place=Stamford, UK: |publisher=Key Publishing, pp.&nbsp;|pages=2–6. {{ISSN|issn=0143-5450}}.
* {{Cite book |last=Pace |first=Steve |title=Lockheed SR-71 Blackbird |location=Swindon, UK |publisher=[[Crowood Press]] |year=2004 |isbn=1-86126-697-9}}
* Remak, Jeannette and Joe Ventolo Jr. ''A-12 Blackbird Declassified''. St. Paul, Minnesota: MBI Publishing Company, 2001. {{ISBN|0-7603-1000-9}}.
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* Grant, R.G. ''Flight: 100 Years of Aviation''. New York: DK Publishing, 2007. {{ISBN|978-0-7566-1902-2}}.
* Hobson, Chris. ''Vietnam Air Losses, USAF, USN, USMC, Fixed-Wing Aircraft Losses in Southeast Asia 1961–1973''. North Branch, Minnesota: Specialty Press, 2001. {{ISBN|1-85780-115-6}}.
* {{Cite conference |last=Merlin, |first=Peter W. [|date=January 2009 |title=Design and Development of the Blackbird: Challenges and Lessons Learned |url=https://ntrs.nasa.gov/archiveapi/nasacitations/casi.ntrs.nasa.gov20090007797/downloads/20090007797.pdf ''Design|conference=47th andAIAA DevelopmentAerospace ofSciences theMeeting Blackbird:including ChallengesThe New Horizons Forum and LessonsAerospace Learned''.]Exposition |location=Orlando, Florida: |publisher=[[American Institute of Aeronautics and Astronautics]] (AIAA), 2009|doi=10.2514/6.2009-1522 |id=AIAA 2009–1522.2009-1522 |access-date=23 June 2024}}
* {{Cite book |last=Merlin, |first=Peter W. [|url=https://bookswww.googlenasa.comgov/books?id=jB_v50Uaab4Cwp-content/uploads/2021/04/88796main_yf-12.pdf ''|title=Mach 3+: NASA /USAF YF-12 Flight Research 1969–1979''.] Washington, D.C.: Diane Publishing Co.,1969-1979 |publisher=NASA History Division Office, |year=2002. {{ISBN|1series=Monographs in aerospace history, #25 |id=NASA SP 2001-42894525 |access-9458-0date=23 June 2024}}.
* Pappas, Terry. [https://books.google.com/books?id=KuYDAAAAMBAJ&pg=PA27 "The Blackbird is Back."] ''Popular Mechanics'', June 1991, pp. 27–31, 104–105.
* [https://www.sr-71.org/blackbird/manual/ ''Sr-71 Blackbird Pilot's Flight Manual''].
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