The SR-71 Blackbird is a high-speed aircraft originally designed by
Kelly Johnson's "
Skunk Works" at
Lockheed. Its design and production was spurred by the
1962 Francis Gary Powers shoot-down over the Soviet Union in a
U-2 high-altitude spy plane. The downing of Powers proved that the USSR had developed
SAM systems which could reach the high altitudes used by American reconnaissance aircraft.
In response, the U.S. turned to the U-2's creator and asked him to produce a follow-on aircraft that would be safe from the new Soviet systems. Johnson and his team of merry maniacs at the Skunk Works decided that this meant the aircraft needed both altitude and extreme speed, since the faster the aircraft the shorter the intercept window for ground-based missiles. The SR-71 was the result; a futuristic, elongated, downright evil-looking (but beautiful) airplane. It was powered by two enormous turbojets, mounted in nacelles on each tiny delta wing.
The aircraft's designed performance envelope meant that the platform had to be viable in many different 'realms' of flight, from slow flight for takeoff and landing through transonic, supersonic and up to hypersonic (Mach 2 and over). The problems of aerodynamics involving the engines themselves took up a great deal of the project effort - in order to allow for supersonic airflow to enter the engines without extinguishing them, the airframe was designed so that the actual bowshock from the nose of the airplane (which normally interferes with engine flow as an aircraft approaches Mach 1) would impinge directly onto the inner surface of the engine nacelles. This allowed maximal 'feeding' of the huge engines. In order to prevent the shockwave from disrupting the airflow, the engine nacelles sported a pair of enormous conical 'inlet cones' that were to be moved independently of the main engine controls. While this allowed the airplane to fly, it introduced yet another flight variable; one of the most common in-flight mishaps (usually, fortunately, not fatal) is an 'inlet stall' which occurs when the inlet cones drift out of their precise positions (which are linked closely to current airspeed). This is similar to a compressor stall.
Perhaps one of the most impressive image of the SR-71 is that of the airplane during a night takeoff, its afterburners carving long tongues of purple flame through the sky. Even more impressive, perhaps, was the traditional burst of flame from the body with which it left the earth. This was due to the presence of fuel leaks, spilling raw fuel into the jetwash.
Actually, it leaked because the fuselage was designed to fit together snugly when heated by the air friction that the aircraft withstood when travelling at its cruising speeds. Although the plane is said to be the fastest one in existence, we can't be sure. It did set the U.S. coast-to-coast speed record of around 1hr. 52mins, measured from a timing gate on a Pacific beach to Washington D.C.
Useless trivia: This plane was originally designated the RS-71. RS stood for Reconnaissance/Strike. Technically, it could carry a single nuclear gravity bomb. However, when it was first publicly announced, President Lyndon Johnson referred to it mistakenly as the SR-71. Since they didn't want to contradict the President of the U.S.A., the Air Force quickly renamed it the SR-71.
There are still a couple of these airplanes in service with NASA. They are used as testbeds for high-speed research; for example, models of SCRAMJETs (which can only begin to work at speeds of Mach 2 and up) have been carried and ignited aboard the plane.
The CIA and the Air Force had Kelly Johnson, the creator of the Skunk Works and the SR-71 and U2, design and build a reconnaissance drone (the D-21?) that was to be launched from the SR-71's dorsal area. It was intended to overfly mainland China and the eastern Soviet Union, taking pictures as it went about its business at Mach 3+. It would then fly back out over the Pacific and rendezvous with friendly naval or air forces. They never got it to work; first of all, releasing it at Mach 3 turned out to be extremely hazardous for the pilot of the SR-71, and although a mission was launched, the drone was never heard from again. So they canned it.
Actually, years later, after the fall of the Soviet Union, one of the men associated with the ill-fated drone project was approached by an acquaintance. The other was a KGB agent, on duty in Washington; he handed the American a piece of black metal and said "Recognize this?" It was a piece of titanium fuselage from the vanished drone - a Mongol farmer had found its crash site, and the KGB had nabbed it. Apparently, pieces of it were popular desktop ornaments inside the Soviet security bureau.
More useless trivia: the airplane is constructed entirely of titanium, in order to withstand the intense heat of friction that it experiences, and to provide the structural strength necessary to handle the immense stresses of hitting turbulence while travelling literally faster than a speeding bullet. The titanium skin expanding causes the aircraft to 'grow' 11 inches while in flight. The continued process of heating and cooling the titanium is akin to annealing, and means that the SR-71 lands with its outer skin in better condition than when it took off.
The jet fuel it uses, JP7, is used ONLY in this aircraft. It is so modified that you can use it to extinguish a match; it will only burn in the SR-71's mammoth engines. There are two hydraulic systems on the aircraft; at Standard temperature and pressure (STP), the hydraulic fluid in the cruise system is in fact a powder. Note: lj points out that reg'lar ol' jet fuel will, in fact, extinguish a match, since having a high flashpoint is a safety feature for jet fuel. I will redraw the trivia; JP7 won't burn in standard jet engines. It will only properly combust in the Blackbird's heart, and requires an additive to start the engines. It can be induced to burn in open air, but it takes a great deal of effort - the above 'flame burst' occurs when vaporizing JP7 is flung into the afterburner exhaust of the SR-71.
There are those who are convinced that there is, in fact, a secret successor to the SR-71 that is presently being flown by U.S. forces. Code-named Aurora by the Area 51 watchers of the Southwest, it is rumored to be a working SCRAMJET airplane which can travel exoatmospheric at speeds of 'over Mach 5.' A recent report by Aviation Week describes an unconfirmed system named Blackstar which may or may not account for these rumors and various sightings.
How true is this? Although it doesn't seem likely that the Air Force would willingly give up their most capable recon platform, which would imply that a more capable alternative was available to them, the sheer engineering challenge of such an aircraft gives me pause.
Of course, they were flying the Stealth fighter for years before acknowledging it.