Lockheed SR-71 Blackbird |
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| Strategic Reconnaissance AC |
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United States Air Force |
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Lockheed SR-71 Program Milestones |
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| The SR-71 Blackbird has set several records both for speed, altitude and time-range. These records can be found here! |
Lockheed SR-71 Aircraft Dimensions |
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| 107 feet 5 inch (32.74 m) |
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| 37 feet 10 inch (11.53 m) |
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Lockheed SR-71 Powerplants |
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Lockheed SR-71 Radius & Performance |
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| Any discussion of the SR-71's performance is limited to declassified information. Actual performance figures will remain the subject of speculation until additional information is released. |
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| Both the "Coast-to-Coast" and NY to London records are seriously impressive compared to flight times accomplished by aircraft like the Aerospatiale BAC Concorde 101 (3 hours 22 minutes) and the Boeing 747-400 (6 hours 15 minutes). During the flight between New York and London the SR-71 achieved an average speed of about Mach 2.68, which includes slowing down for in-flight refueling. |
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| Lockheed SR-71 Blackbird Information |
The Lockheed SR-71 "Blackbird" is a long-range, advanced, strategic reconnaissance aircraft developed from the Lockheed YF-12A and A-12 aircraft by the Lockheed Skunk Works. Besides its mighty appearance, the SR-71 was capable of achieving speeds above Mach 3 and was nicknamed "Blackbird". Besides flying fast, the aircraft could fly very high as well and was used as a defensive feature. In case a surface-to-air missile launch were detected, standard evasive action was simply to accelerate. The SR-71 line was in service from 1964 to 1998, with 12 of the 32 aircraft being destroyed in accidents, though none were lost during warfare.
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Click for a large image |
Click for a large image |
Click for a large image |
The predecessor of the SR-71, was the A-12 OXCART and was specifically designed for the CIA by Kelly Johnson. As the design evolved, the internal Lockheed designation progressed from A-1 to A-12 as config changes occurred. The first flight took place at Groom Lake, Nevada, on April 25, 1962. It was operated by an A-12 and was equipped with less powerful Pratt & Whitney J75 turbojet engines due to protracted development of the intended Pratt & Whitney J58. Later the J58 engine became the standard powerplant for all subsequent aircraft in the series, including the follow-on SR-71 aircraft.
In total, eighteen A-12 family aircraft have been built of which one was a pilot trainer, having a raised second cockpit for an instructor-pilot, and 12 were reconnaissance A-12s to be flown operationally by CIA pilots. The other 5 consisted of three YF-12As, prototypes of the planned F-12B interceptor version, and two were the M-21 variant (see later).
At first, the United States Air Force planned to redesignate the A-12 aircraft as the B-71; successor of the B-70 Valkyrie. The aircraft would have a nuclear capability of three first-generation SRAMs, or Short-Range Attack Missiles). The next designation was RS-71 after the strike capability became an option. However, Chief of Staff, at that time Curtis Lemay, preffered the SR (Strategic Reconnaissance) designation and wanted the RS-71 to be named SR-71. Before its announciation by President Johnson on February 29, 1964, Lemay lobbied to modify Johnson's speech to read SR-71 instead of RS-71. Following Johnson's speech the name change was taken as an order from the Commander-in-Chief, and immediate reprinting began of new materials, including 29,000 blueprints, to be retitled "SR-71".
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| Lockheed SR-71 Blackbird Design |
| The airframe of the SR-71 is made of titanium obtained from the USSR during the height of the Cold War. In order to control costs, Lockheed used a more easily-worked alloy of titanium which softened at a lower temperature. In order to increase the emission of internal heat, finished aircraft were painted dark blue which also act as camouflage against the sky.
Furthermore, the SR-71 was designed to minimize radar cross-section, and was an early attempt to stealth design. Ironically, because of the extremely hot particles in the exhaust of the engines, the Blackbird was one of the largest targets on the FAA long-range radars.
In order to prevent damage to the skin of the aircraft, red stripes are found on some of the SR-71s. The curved skin near the centre of the fuselage is thin and delicate and there is no support underneath it with exception of the structural ribs, which are spaced several feet apart.
Engine air inlets
In order to achieve cruise speeds of over Mach 3.2 the engine air inlets were a critical design feature. The front end of each inlet had a sharp movable cone called a "spike" that was locked in the full forward position on the ground or when in subsonic flight. During acceleration to high-speed cruise, the spike would unlock at Mach 1.6 and then begin a mechanical travel to the rear. The original air inlet computer was an analog design which, based on pitot-static, pitch, roll, yaw, and angle-of-attack inputs, would determine how much movement was required.
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However, in the early years of the Blackbird programs, the analog air inlet 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". Eventually this could result in an immediate stop of flow of air through the engine compressor while subsequent exhaust gas temperatures would begin to rise. The tremendous amount of thrust of the remaining engine would cause asymmetrical push causing violent yawing to one side. Often the extreme off-angle would reduce airflow in the opposite engine and cause it to begin "sympathetic stall". The result would be rapid counter-yawing, often loud "banging" noises and a rough ride. The crews' pressure-suit helmets would sometimes bang on the cockpit canopies until the intial unstart motions subsided.
Later the analog air inlet computer was replace by a digital one. Lockheed engineers developed control software for the engine inlets that would recapture the lost shock wave and relight the engine before the pilot was even aware an unstart had occurred.
Engines
The Pratt & Whitney J58-P4 engines powering the Blackbird, were the only military engines ever designed to operate continuously on afterburner. In contrast with conventional jet engines, they became more efficient as the aircraft went faster while "normal" engines would lose efficiency as airspeed increases. The J58 was unique in that it was a hybrid jet engine and could operate as a regular turbojet at low speeds, but became a ramjet at high speeds. At lower speeds, the turbojet provided most of the compression and most of the engergy from fuel combustion. At higher speeds, the turbojet throttled back and just sat in the middle of the engine as air bypassed around it, having been compressed by the shock cones and only burning fuel in the afterburner.
Fuel
In the developement stage of the SR-71, a coal slurry powerplant was planned to power the aircraft. However, Johnson determined that the coal particles would damage engine components and he began researching a liquid hydrogen powerplant. Since the tanks required to store cryogenic hydrogen, this type of fuel did not suit the Blackbird's form factor and the focus became more conventional, though still specialized in many ways. Eventually, JP-7 jet fuel was selected to be used on the SR-71. This type of fuel was very slippery and extremely difficult to light in any conventional way. Although its slipperiness was a disadvantage on the ground, it was not a fire hazard. When the engines were started, puffs of tetraethylborane were injected into the engines in order to produce temperatures high enough to initially ignite the JP-7.
Chines
One of the most interesting and unique features of the SR-71 are the chines themselves. Although the SR-71 was not originally designed having these chines since Lockheed's aerodynamicists were concered that these surfaces would hurt aerodynamic performance, government agencies paying for the project wanted drastically reduced radar cross-section, and eventually pushed them to try chines on a few wind-tunnel models. Aerodynamicists discovered that the chines generated powerful vortices around themselves, generating much additional lift near the front of the aircraft, leading to improvements in aerodynamic performance. Other aircraft that incorporate such a feature include the F-5, F-16, F/A-18, MIG-29 and Su-27.
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