North American XB-70 Valkyrie

The North American Aviation XB-70 Valkyrie is the prototype of the B-70 nuclear-armed, deep-penetration strategic bomber for the U.S. Air Force's Strategic Air Command. North American Aviation designed the Valkyrie bomber as a large, six-engined aircraft capable of reaching Mach 3+ while flying at 70,000 feet (21,000 m).

At these speeds, it was expected that the B-70 would be almost immune to interceptor aircraft, the only effective weapon against bomber aircraft at the time. The bomber would spend only a few minutes over a particular radar station, flying out of its range before the controllers could position their fighters in a suitable location for an interception. Its high speed also made the aircraft difficult to see on the radar displays, and its high altitude flight could not be matched by any contemporary Soviet fighter.

The introduction of the first Soviet surface-to-air missiles in the late 1950s put the near-invulnerability of the B-70 in doubt. In response, the US Air Force began flying its missions at low level, where the missile radar's line of sight was limited by local terrain. In this low-level penetration role, the B-70 offered little additional performance over the B-52 it was meant to replace. It was, however, far more expensive and had shorter range. Other alternate missions were proposed, but these were of limited scope. As the strategic role passed from bombers to intercontinental ballistic missiles (ICBMs) during the late 1950s, manned bombers were increasingly seen as an anachronism.

North America

North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere. It can also be considered a northern subcontinent of the Americas. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, and to the southeast by South America and the Caribbean Sea.

North America covers an area of about 24,709,000 square kilometers (9,540,000 square miles), about 16.5% of the earth's land area and about 4.8% of its total surface. North America is the third largest continent by area, following Asia and Africa, and the fourth by population after Asia, Africa, and Europe.

In 2013, its population was estimated at nearly 565 million people in 23 independent states, or about 7.5% of the world's population, if nearby islands (most notably the Caribbean) are included.

North America was reached by its first human populations during the last glacial period, via crossing the Bering land bridge. The so-called Paleo-Indian period is taken to have lasted until about 10,000 years ago (the beginning of the Archaic or Meso-Indian period). The Classic stage spans roughly the 6th to 13th centuries. The Pre-Columbian era ended with the arrival of European settlers during the Age of Discovery and the Early Modern period. Present-day cultural and ethnic patterns reflect different kind of interactions between European colonists, indigenous peoples, African slaves and their descendants. European influences are strongest in the northern parts of the continent while indigenous and African influences are relatively stronger in the south. Because of the history of colonialism, most North Americans speak English, Spanish or French and societies and states commonly reflect Western traditions.

Air force

An air force, also known in some countries as an air army, is in the broadest sense, the national military organization that primarily conducts aerial warfare. More specifically, it is the branch of a nation's armed services that is responsible for aerial warfare as distinct from an army, navy, or a marine corps. Typically, air forces are responsible for gaining control of the air, carrying out strategic and tactical bombing missions, and providing support to land and naval forces.

The term "air force" may also refer to a tactical air force or numbered air force, which is an operational formation either within a national air force or comprising several air components from allied nations. Air forces typically consist of a combination of fighters, bombers, helicopters, transport planes and other aircraft.

Many air forces are also responsible for operations of the military space, intercontinental ballistic missiles (ICBM), and communications equipment. Some air forces may command and control other air defence assets such as anti-aircraft artillery, surface-to-air missiles, or anti-ballistic missile warning networks and defensive systems. Some nations, principally Russia, the former Soviet Union and countries who modelled their militaries along Soviet lines, have an air defence force which is organizationally separate from their air force.

United States military aircraft designation systems

The United States Military Aircraft Designation System was first designed in 1919 when the US Army's Aeronautical Division became the United States Army Air Service. Before this aircraft were put into service under their manufacturers' designations.

History

United States Army Air Service 1919 to 1924

During this period Type Designations used by the United States Army Air Service were allotted, using two or three letters, which were an abbreviation of the aircraft's purpose. Examples include GA for Ground Attack aircraft; NO for Night Observation aircraft and NBS for Night Bombardment, Short Distance aircraft.

Army aviation 1924 to 1962

From 1924 to 1947 the Air Service, United States Army Air Corps, United States Army Air Forces and United States Air Force used a designation system based on mission category, with each model in a category numbered sequentially. In 1947, the designation system was extensively overhauled, with several categories being dispensed with, and others renamed For instance, the Lockheed P-80 Shooting Star (Pursuit) was redesignated as F-80 (Fighter), while the A-26 medium bomber/attack aircraft was redesignated as the B-26, reusing the designation, the Martin B-26 having retired in the meantime.

Valkyrie

In Norse mythology, a valkyrie (from Old Norse valkyrja "chooser of the slain") is one of a host of female figures who choose those who may die in battle and those who may live. Selecting among half of those who die in battle (the other half go to the goddess Freyja's afterlife field Fólkvangr), the valkyries bring their chosen to the afterlife hall of the slain, Valhalla, ruled over by the god Odin. There, the deceased warriors become einherjar (Old Norse "single (or once) fighters"). When the einherjar are not preparing for the events of Ragnarök, the valkyries bear them mead. Valkyries also appear as lovers of heroes and other mortals, where they are sometimes described as the daughters of royalty, sometimes accompanied by ravens and sometimes connected to swans or horses.

Valkyries are attested in the Poetic Edda, a book of poems compiled in the 13th century from earlier traditional sources; the Prose Edda and Heimskringla (by Snorri Sturluson), and Njáls saga, a Saga of Icelanders, all written in the 13th century. They appear throughout the poetry of skalds, in a 14th-century charm, and in various runic inscriptions.