Lockheed SR-71 Blackbird

SR-71 "Blackbird"
Dryden's SR-71B Blackbird, NASA 831, slices across the snow-covered southern Sierra Nevada Mountains of California after being refueled by an Air Force tanker during a 1994 flight. SR-71B was the trainer version of the SR-71. The dual cockpit to allow the instructor to fly.
An SR-71B trainer over the Sierra Nevada Mountains of California in 1994. The raised second cockpit is for the instructor.
RoleStrategic reconnaissance aircraft
National originUnited States
ManufacturerLockheed, Skunk Works division
DesignerClarence "Kelly" Johnson
First flight22 December 1964
IntroductionJanuary 1966
Retired1998 (USAF), 1999 (NASA)
StatusRetired
Primary usersUnited States Air Force
NASA
Number built32
Unit cost
$34 million[1]
Developed fromLockheed A-12

The Lockheed SR-71 "Blackbird" is a long-range, Mach 3+ strategic reconnaissance aircraft that was operated by the United States Air Force.[2] It was developed as a black project from the Lockheed A-12 reconnaissance aircraft in the 1960s by Lockheed and its Skunk Works division. American aerospace engineer Clarence "Kelly" Johnson was responsible for many of the design's innovative concepts. During aerial reconnaissance missions, the SR-71 operated at high speeds and altitudes to allow it to outrace threats. If a surface-to-air missile launch were detected, the standard evasive action was simply to accelerate and outfly the missile.[3] The shape of the SR-71 was based on the A-12 which was one of the first aircraft to be designed with a reduced radar cross-section.

The SR-71 served with the U.S. Air Force from 1964 to 1998. A total of 32 aircraft were built; 12 were lost in accidents but none lost to enemy action.[4][5] The SR-71 has been given several nicknames, including "Blackbird" and "Habu".[6] Since 1976, it has held the world record for the fastest air-breathing manned aircraft, a record previously held by the related Lockheed YF-12.[7][8][9]

Development

Background

Lockheed's previous reconnaissance aircraft was the relatively slow U-2, designed for the Central Intelligence Agency (CIA). In late 1957, the CIA approached the defense contractor Lockheed to build an undetectable spy plane. The project, named Archangel, was led by Kelly Johnson, head of Lockheed's Skunk Works unit in Burbank, California. The work on project Archangel began in the second quarter of 1958, with aim of flying higher and faster than the U-2. Of 11 successive designs drafted in a span of 10 months, "A-10" was the frontrunner. Despite this, however, its shape made it vulnerable to radar detection. After a meeting with the CIA in March 1959, the design was modified to have a 90% reduction in radar cross-section. The CIA approved a US$96 million contract for Skunk Works to build a dozen spy planes, named "A-12" on 11 February 1960. The 1960 downing of Francis Gary Powers's U-2 underscored its vulnerability and the need for faster reconnaissance aircraft such as the A-12.[10]

The A-12 first flew at Groom Lake (Area 51), Nevada, on 25 April 1962. Thirteen were built; two variants were also developed, including three of the YF-12 interceptor prototype, and two of the M-21 drone carrier. The aircraft was meant to be powered by the Pratt & Whitney J58 engine, but development ran over schedule, and it was equipped instead with the less powerful Pratt & Whitney J75 initially. The J58s were retrofitted as they became available, and became the standard powerplant for all subsequent aircraft in the series (A-12, YF-12, M-21), as well as the SR-71. The A-12 flew missions over Vietnam and North Korea before its retirement in 1968. The program's cancellation was announced on 28 December 1966,[11] due both to budget concerns[12] and because of the forthcoming SR-71, a derivative of the A-12.[13]

SR-71

Blackbird on the assembly line at Lockheed Skunk Works
SR-71 Blackbird assembly line at Skunk Works

The SR-71 designation is a continuation of the 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.[14]

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 performance potential clearly was found to be much greater, the Air Force ordered a variant of the A-12 in December 1962.[15] Originally named R-12[N 1] by Lockheed, the Air Force version was longer and heavier than the A-12, with a longer fuselage to hold more fuel, two seats in the cockpit, and reshaped chines. Reconnaissance equipment included signals intelligence sensors, a side-looking airborne radar, and a photo camera.[15] The CIA's A-12 was a better photo-reconnaissance platform than the Air Force's R-12, since the A-12 flew somewhat higher and faster,[12] and with only one pilot, it had room to carry a superior camera[12] and more instruments.[16]

During the 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 Air Force interceptor, which also served as cover for the still-secret A-12[17] and the Air Force reconnaissance model since July 1964. Air Force 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.[18][N 2] Johnson only referred to the A-11 to conceal the A-12, while revealing that there was a high speed, high altitude reconnaissance aircraft.[19]

In 1968, Secretary of Defense Robert McNamara cancelled the F-12 interceptor program; the specialized tooling used to manufacture both the YF-12 and the SR-71 was also ordered destroyed.[20] Production of the SR-71 totaled 32 aircraft with 29 SR-71As, two SR-71Bs, and the single SR-71C.[21]

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