美国隐形轰炸机B2.docx

1、美国隐形轰炸机B2Northrop Grumman B-2 SpiritOverviewThe Northrop (later Northrop Grumman) B-2 Spirit, also known as the Stealth Bomber, is an American heavy strategic bomber, featuring low observable stealth technology designed for penetrating dense anti-aircraft defenses; it is a blended wing body design w

2、ith a crew of two. The bomber can deploy both conventional and thermonuclear weapons, such as eighty 500 lb (230 kg)-class (Mk 82) JDAM Global Positioning System-guided bombs, or sixteen 2,400 lb (1,100 kg) B83 nuclear bombs. The B-2 is the only known aircraft that can carry large air-to-surface sta

3、ndoff weapons in a stealth configuration.Development originally started under the Advanced Technology Bomber (ATB) project during the Carter administration, and its performance was one of his reasons for the cancellation of the supersonic B-1A bomber. ATB continued during the Reagan administration,

4、but worries about delays in its introduction led to the reinstatement of the B-1 program as well. Program costs rose throughout development. Designed and manufactured by Northrop Grumman, the cost of each aircraft averaged US$737 million (in 1997 dollars). Total procurement costs averaged $929 milli

5、on per aircraft, which includes spare parts, equipment, retrofitting, and software support. The total program cost including development, engineering and testing, averaged $2.1 billion per aircraft in 1997.Because of its considerable capital and operating costs, the project was controversial in the

6、U.S. Congress and among the Joint Chiefs of Staff. The winding-down of the Cold War in the latter portion of the 1980s dramatically reduced the need for the aircraft, which was designed with the intention of penetrating Soviet airspace and attacking high-value targets. During the late 1980s and 1990

7、s, Congress slashed plans to purchase 132 bombers to 21. In 2008, a B-2 was destroyed in a crash shortly after takeoff, though the crew ejected safely. A total of 20 B-2s remain in service with the United States Air Force, which plans to operate the B-2 until 2058.The B-2 is capable of all-altitude

8、attack missions up to 50,000 feet (15,000 m), with a range of more than 6,000 nautical miles (11,000 km) on internal fuel and over 10,000 nautical miles (19,000 km) with one midair refueling. Though originally designed primarily as a nuclear bomber, it was first used in combat dropping conventional

9、ordnance in the Kosovo War in 1999 and saw further service in Iraq and Afghanistan.DesignThe B-2 Spirit was developed to take over the USAFs vital penetration missions, able to travel deep into enemy territory to deploy their ordnance, which could include nuclear weapons. The B-2 is a flying wing ai

10、rcraft, meaning it has no fuselage or tail. The blending of low-observable technologies with high aerodynamic efficiency and large payload gives the B-2 significant advantages over previous bombers. Low observability provides a greater freedom of action at high altitudes, thus increasing both range

11、and field of view for onboard sensors. The U.S. Air Force reports its range as approximately 6,000 nautical miles (6,900 mi; 11,000 km). At cruising altitude the B-2 refuels every six hours, taking on up to 50 short tons (45 t) of fuel at a time.Due to the aircrafts complex flight characteristics an

12、d design requirements to maintain very-low visibility to multiple means of detection, both the development and construction of the B-2 required pioneering use of computer-aided design and manufacturing technologies. The B-2 bears a resemblance to earlier Northrop aircraft: the YB-35 and YB-49 were b

13、oth flying wing bombers that had been canceled in development in the early 1950s, allegedly for political reasons. The resemblance goes as far as B-2 and YB-49 having the same wingspan.As of September 2013 about 80 pilots fly the B-2. Each aircraft has a crew of two, a pilot in the left seat and mis

14、sion commander in the right, and has provisions for a third crew member if needed. For comparison, the B-1B has a crew of four and the B-52 has a crew of five. The B-2 is highly automated and, unlike most two-seat aircraft, one crew member can sleep in a camp bed, use a toilet, or prepare a hot meal

15、 while the other monitors the aircraft; extensive sleep cycle and fatigue research was conducted to improve crew performance on long sorties.Armaments and equipmentThe B-2, in the envisaged Cold War scenario, was to perform deep-penetrating nuclear strike missions, making use of its stealthy capabil

16、ities to avoid detection and interception throughout missions. There are two internal bomb bays in which munitions are stored either on a rotary launcher or two bomb-racks; the carriage of the weapons loadouts internally results in less radar visibility than external mounting of munitions. The B-2 i

17、s capable of carrying 40,000 pounds of ordnance. Nuclear ordnance includes the B61 and B83 nuclear bombs; the AGM-129 ACM cruise missile was also intended for use on the B-2 platform.It was decided, in light of the dissolution of the Soviet Union, to equip the B-2 for conventional precision attacks

18、as well as for the strategic role of nuclear-strike. The B-2 features a sophisticated GPS-Aided Targeting System (GATS) that uses the aircrafts APQ-181 synthetic aperture radar to map out targets prior to deployment of GPS-aided bombs (GAMs), later superseded by the Joint Direct Attack Munition (JDA

19、M). In the B-2s original configuration, up to 16 GAMs or JDAMs could be deployed; an upgrade program in 2004 raised the maximum carriable capacity to 80 JDAMs.The B-2 has various conventional weapons in its arsenal, able to equip Mark 82 and Mark 84 bombs, CBU-87 Combined Effects Munitions, GATOR mi

20、nes, and the CBU-97 Sensor Fuzed Weapon. In July 2009, Northrop Grumman reported the B-2 was compatible with the equipment necessary to deploy the 30,000 lb (14,000 kg) Massive Ordnance Penetrator (MOP), which is intended to attack reinforced bunkers; up to two MOPs could be equipped in the B-2s bom

21、b bays, the B-2 is the only platform compatible with the MOP as of 2012. As of 2011, the AGM-158 JASSM cruise missile is an upcoming standoff munition to be deployed on the B-2 and other platforms. This is to be followed by the Long Range Standoff Weapon which may give the B-2 a standoff nuclear cap

22、ability for the first time.Avionics and systemsIn order to make the B-2 more effective than previous bombers, many advanced and modern avionics systems were integrated into its design, these have been modified and improved following a switch to conventional warfare missions. One system is the low pr

23、obability of intercept AN/APQ-181 multi-mode radar, a fully digital navigation system that is integrated with terrain-following radar and Global Positioning System (GPS) guidance, NAS-26 astro-inertial navigation system (first such system tested on the Northrop SM-62 Snark cruise missile) and a Defe

24、nsive Management System (DMS) to inform the flight crew of possible threats. The onboard DMS is capable of automatically assessing the detection capabilities of identified threats and indicated targets. For safety and fault-detection purposes, an on-board test system is interlinked with the majority

25、 of avionics on the B-2 to continuously monitor the performance and status of thousands of components and consumables; it also provides post-mission servicing instructions for ground crews. In 2008, many of the 136 standalone distributed computers on board the B-2, including the primary flight manag

26、ement computer, were being replaced by a single integrated system. The avionics are controlled by 13 EMP-resistant MIL-STD-1750A computers, which are interconnected through 26 MIL-STD-1553B-busses; other system elements are connected via optical fiber.In addition to periodic software upgrades and th

27、e introduction of new radar-absorbent materials across the fleet, the B-2 has had several major upgrades to its avionics and combat systems. For battlefield communications, both Link-16 and a high frequency satellite link have been installed, compatibility with various new munitions has been underta

28、ken, and the AN/APQ-181 radars operational frequency was shifted in order to avoid interference with other operators equipment. The arrays of the upgraded radar features were entirely replaced to make the AN/APQ-181 into an active electronically scanned array (AESA) radar.To keep the B-2 relevant ag

29、ainst increasingly sophisticated air defenses with greater computer processing power that may be able to detect the aircraft through its stealth measures, the Air Force is working to upgrade the Defensive Management System (DMS), which uses sensors, passive receivers, and computers to alert crew abo

30、ut the location of enemy air defense systems. Though it will not counter air threats, it will be more capable of identifying and locating them before the aircraft enters strike range. The upgraded DMS will help detect radar emissions from air defenses to allow changes to the auto-routers mission pla

31、nning information while in-flight so it can receive new data quickly to plan a route that minimizes exposure to dangers. The DMS upgrade is slated to enter service by 2021.Flight controlsIn order to address the inherent flight instability of a flying wing aircraft, the B-2 uses a complex quadruplex

32、computer-controlled fly-by-wire flight control system, that can automatically manipulate flight surfaces and settings without direct pilot inputs in order to maintain aircraft stability. The flight computer receives information on external conditions such as the aircrafts current air speed and angle

33、 of attack via pitot-static sensing plates, as opposed to traditional pitot tubes which would negatively affect the aircrafts stealth capabilities. The flight actuation system incorporates both hydraulic and electrical servoactuated components, and it was designed with a high level of redundancy and fault-diagnostic capabilities.Nor