|Northrop B-2 "Spirit"|
A B-2 "Spirit" over the Pacific Ocean
July 17, 1989
17th December 1993
1988 to 1997
|Number of pieces:||
The Northrop B-2 Spirit is a four-engine strategic bomber produced by the US manufacturer Northrop . As flying wing designed B-2 is the most famous stealth bomber ( English stealth bomber ) and is considered the most expensive by far combat aircraft in the world. It is used exclusively by the United States Air Force .
The B-2 is a design that has been optimized with regard to stealth technology , which means that it is much more difficult to detect and combat than conventional bombers. Originally, the aircraft was designed as a nuclear weapon carrier, which was supposed to bypass Soviet air defense in the event of a conflict , in order to then fight enemy targets deep in the hinterland with a large number of nuclear weapons. After the end of the Cold War , however, numerous modifications were made in order to be able to use a wide range of conventional and precision-guided air-to-ground weapons.
Development and history
The origins of the B-2 can be traced back to 1974. At this point, DARPA , a new technology research organization for the U.S. armed forces, began studying aircraft as part of the Harvey project (the name is an ironic reference to the invisible rabbit that accompanies James Stewart in the movie My Friend Harvey ) low probability of detection. Although the Air Force had already made experience with such aircraft ( Lockheed SR-71 and Lockheed U-2 ), they could not rely solely on their stealth properties, but had to increase their safety through high altitudes and speed. The Harvey project , however, was to produce a machine that was fully protected by its stealth properties. In January 1975 McDonnell Douglas and Northrop received orders for corresponding designs. Lockheed employees became aware of the project and a study was also carried out there at their own expense. This paid off, as DARPA selected Northrop and Lockheed to develop models called Experimental Survivable Testbed (XST). The XSTs were not airworthy but had full radar cross-section and were used for radar tests at Holloman Air Force Base .
In March 1976, Lockheed was announced as the winner of the tender because the design offered better all-round steal properties and Lockheed had more experience with radar absorbing materials (RAM). The company then developed two more airworthy demonstrators, called Have Blue . The F-117 "Nighthawk" emerged from these machines .
Northrop was out of the competition for the Experimental Survivable Testbed , but in December 1976 DARPA contacted the company again, asking for proposals for the United States Department of Defense's new " Assault Breaker " program . The project was intended to produce an aircraft that would fight the outnumbered Soviet tank units far behind the front lines in a war in Europe . This required a high level of survivability, modern sensors and the ability to use precision-guided ammunition . The project was divided into a reconnaissance plane and a weapon carrier, with Northrop supposed to manufacture the former. This model was called Battlefield Surveillance Aircraft - Experimental (BSAX) and was supposed to provide target data for the weapon-carrying machine. Since it was supposed to patrol an area longer, great importance was attached to good steal properties from all angles. In 1977 a first prototype was completed and tested. The test results were unsatisfactory and a new design was submitted. In April 1978, the DARPA Northrop then gave the order to manufacture a new airworthy prototype, which was called Tacit Blue (German: "still blue").
The first flight of the prototype took place in February 1982, followed by 134 more flights over the next three years. In 1984 the Air Force decided that they would procure a reconnaissance platform without stealth technology . The choice fell on a modified Boeing 707 , from which the E-8 "Joint Stars" emerged . The Tacit Blue prototype was therefore not developed any further.
The ATB program
While Northrop was still working on the Tacit Blue demonstrator, a new study was commissioned within the Pentagon. A stealth machine was planned, which should be able to fully independently detect targets and fight them precisely. Lockheed submitted a draft relatively quickly, which was essentially an enlarged F-117. Nevertheless, the Pentagon also asked Northrop to submit a concept. The company drew on a concept that it had developed more than 30 years ago: the flying wing , with the YB-49 as a prototype. The primary argument for this radical approach, compared to conventional constructions, was the significantly better stealth properties. In August 1979 the proposals were finally submitted under the name “Advanced Strategic Penetration Aircraft” (ASPA). In September 1980 the Air Force formalized the requirements for the “Advanced Technology Bomber” program (ATB). For this competition, Lockheed teamed up with Rockwell and Northrop with Boeing .
In October 1981, the Air Force announced that the Northrop concept, code-named " Senior Ice ", had won the tender. The subsequent development contract included two cells for static ground tests, an airworthy prototype and five additional test machines. Information on Lockheed's competing design, known as the "Senior Peg", was kept confidential until 2005.
Manufacturing and implementation
Before series production, a four-engine test aircraft on a scale of 1: 2 was most likely manufactured in order to enable more precise estimates of the radar cross-section . In 1986, a full-size engineering model was built in a closed Ford automobile plant near Pico Rivera , and the last major changes were made to it. The facility is considered to be the largest industrial site in the United States that is subject to the strictest secrecy. Despite the 12,000 employees, practically no secret information was leaked. In the case of series production, only the latest available manufacturing technologies were used, with particular reference to the computer-controlled sections. The Air Force then released two billion US dollars for the first machine in November 1987. In early 1986, US Senator Barry Goldwater , Chairman of the Senate Defense Committee, officially announced that the stealth bomber would be included in the US Air Force as a long-range bomber in 1991.
On April 20, 1988, the project was presented to the public by publishing a relatively detailed drawing of the machine, previously there were only schematic drawings from the press. At the same time, the maiden flight was announced for the autumn of the same year. On November 22nd, the rollout of the first B-2 took place in front of invited guests. The stands were arranged in such a way that only the front part of the machine was visible, while the rear was hidden. However, Michael A. Dornheim, a reporter from Aviation Week , managed to fly over the scene in a small aircraft and photograph the B-2 from above. This legal action brought the magazine a lot of media attention and is still considered its most spectacular story to this day. The program was continued unchanged and on July 17, 1989 the first flight of the B-2 took place. It flew from the halls of the Lockheed Advanced Development Projects Unit (better known as "Skunk Works") to nearby Edwards Air Force Base . On board were Northrop's test pilot Bruce Hinds and Colonel Richard Couch of the Air Force. On September 23, 1989, the first test flight with air refueling took place on a KC-10 .
Initially, the procurement of 132 copies of the machine was planned, but at the end of the Cold War this was cut to a total of 21 pieces (16 series machines and 5 pre-series aircraft converted to series machines) due to the enormous costs. However, only 20 machines were in use, as one machine is permanently stationed at Edwards Air Force Base for test and development purposes. 19 of these machines were named after US states with a prefixed “Spirit”, starting with the “Spirit of Missouri”, the only exception being the “Spirit of Kitty Hawk ” , which is dedicated to North Carolina . The last B-2 was named "Spirit of America".
The B-2 was first used in 1999 during the war in Kosovo . Two bombers ("Block 30" configuration) of the 509th Bomb Wing took off from Whiteman Air Force Base in Missouri on the morning of March 25 to attack targets in Yugoslavia after several air refueling . This included communications facilities, air defense systems, airports and barracks classified as important . The entire mission, during which each bomber dropped 16 JDAM precision bombs, lasted 31 hours. On the night of May 7th or 8th, a B-2 dropped five JDAMs, which hit the Chinese embassy in Belgrade . According to American statements, this was the result of incorrect intelligence information. By the end of the conflict in June, the B-2 fleet had flown a total of 32 sorties and dropped over 500 JDAMs. There were no losses or damage of our own.
Six B-2s were used in the main fighting during the Afghan War in late 2001. The longest combat mission in aviation history was also carried out here: it lasted a total of 44 hours. The planes were stationed at Whiteman Air Force Base, from where they flew attacks on targets in Afghanistan, only to be refueled and armed with the engines running after landing at Andersen Air Force Base - on the Pacific island of Guam . They then flew again attacks against targets in Afghanistan and finally returned to Whiteman Air Force Base.
During the Iraq war in spring 2003 four B-2 machines were used. The machines completed 49 missions, 27 of which were again flown from Whiteman Air Force Base. The remaining 22 flights were operated from Diego Garcia and Guam . The four B-2 bombers dropped around 700 tons of bombs, including 583 JDAMs , during the Gulf War .
Since the maintenance of the sensitive hull of the aircraft requires an air-conditioned hangar that is large enough for the wingspan, a relocatable hangar, the Extra Large Deployable Aircraft Hangar System with a width of 76 m, a length of 38 m and developed to a height of 18 m. A total of ten of them were erected in Diego Garcia , Guam and Fairford in order to be able to station and maintain the B-2 closer to their locations.
On February 23, 2008 a B-2 was lost. The machine with the name "Spirit of Kansas" (AV-12, registration number 89-0127) had an accident while taking off at Andersen Air Force Base, whereby both pilots were able to save themselves with the ejection seats. The pilot was slightly injured, the copilot seriously injured. The cause was moisture in a sensor that provided data for flight attitude control. Contrary to the regulations, the sensor was not dried by heating before calibration. Due to the incorrect data from the sensor, the flight attitude control steered the aircraft into an angle of attack that was too steep when taking off , which led to a stall and thus to a crash.
Technology and construction
According to an investigation report by the General Accounting Office , the coating is sensitive to moisture and heat.
The B-2 is a flying wing ; It therefore has no vertical stabilizers , which contributes significantly to reducing the radar cross-section . The structure and the surface consist for the most part (about 90%) of carbon fiber reinforced plastic connected by means of epoxy resin . In order to keep the radar signature low, the wing was constructed with as few structure-disrupting elements as possible. These elements include, above all, maintenance hatches , which have been reduced to a minimum and are largely located on the top, where radiation from radar systems is very unlikely. Many maintenance-relevant assemblies of the machine have been combined in such a way that they can also be reached through any entrances (e.g. the cockpit access and the landing gear shafts). The entire shape of the machine is made soft and flowing in order to avoid radar location through sharp edges or similar structures. This required extremely precise production of the surface structure, which was completely computer-aided and had tolerances of just 0.025 mm. Great importance was attached to simplicity in the front profile: the two moderately swept wing leading edges meet at the bow, which means that radar signals are not reflected in the direction of flight. The W-shaped tail serves the same purpose, but it also houses the sophisticated flap system for flight control.
This consists of a total of nine flaps, eight of which are attached symmetrically to each other. The outer pair consists of two independently expandable flaps that are responsible for yawing and also act as an air brake . Since flaps are structure-disrupting elements, they enlarge the radar cross-section, which is why this pair of flaps is brought into an optimal position from a stealth point of view during combat operations. During the landing approach, the flaps remain slightly open to ensure directional stability. The yaw is then prevented by different thrust control of the four engines. The next three pairs are all designed as elevons . The ninth flap is located in the middle of the stern (also known as the "beaver tail") and acts as an elevator . The sunken suspensions of the control surfaces were initially prone to failure and have a short service life (due to the lack of counterweights). The overall design enables the B-2 to roll rates that are on par with the F-117.
The area around the four engines is particularly complex. These are located in pairs in two distinctive engine bays to the right and left of the cockpit. The air inlets are located on the top as they are better protected from ground-based radar systems there. However, since the B-2 is also to carry out low-level missions and powerful airborne radars (e.g. those from AWACS machines) are part of the threat spectrum, measures have nevertheless been taken to avoid signatures in this area. The zigzag pattern ensures efficient scattering of frontal electromagnetic waves. The engines are located deep inside the wing, where their fan blades prevent electromagnetic waves from being reflected by means of S-shaped structures in the air inlet that are provided with radar-absorbing materials . Since the B-2 should also have reduced emissions in the infrared range , the exhaust jet from the engines had to be cooled. For this purpose, cool air is taken from the boundary layer below the main inlet at the air inlet in order to mix it with the hot exhaust gases at the end of the engine. The somewhat cooler exhaust gases are then directed onto a surface made of heat-resistant carbon fiber elements and titanium alloys , which distribute the exhaust gas stream laterally in order to accelerate its further cooling. The engines are also soundproofed to avoid acoustic localization, especially at low altitude.
Immediately behind the main landing gear shafts there are two more shafts in which systems for eliminating contrails using a chlorine - fluorine - sulfuric acid were originally intended to be housed. However, this plan was discarded because the acid was problematic in storage due to its strong corrosive effect and also caused a clear signature in the UV spectrum. Instead, a laser was installed in the stern area , which detects possible contrail formation and reports it to the pilots, so that a suitable flight altitude can be avoided. The two shafts remained free and offer space for future upgrades such as jamming systems or small guided weapons .
The entire bomb load of the B-2 is housed in two weapon bays. They are equipped with a rotating release system, of which there are different types that can be exchanged depending on the mission. The flaps of the shafts are provided with a zigzag pattern, similar to the engine inlets, in order to be able to attenuate possible echo signals through multiple reflections and to be able to better disperse them. The B-2 can also be air-fueled ; the corresponding opening, which is covered by a flap during the cruise flight to improve the steal properties, is located behind the cockpit on the top of the machine.
The B-2 also uses radar absorbing materials , but not like the F-117 on the entire surface. Particular attention was paid to at least the leading edge of the wing, which due to its internal structure (most likely pyramid-shaped absorber or a sawtooth pattern) emits extremely little radar energy. Overall, almost all edges, including those of the maintenance hatches or engine inlets and outlets, were arranged in such a way that incident transmission pulses from radar devices are only reflected directly to the transmitter in four extremely narrow angular ranges: 35 °, 145 °, 215 ° and 325 °. In these narrow areas (≈ 1% of the possible angle) of the edges caused by increases radar cross section (engl. Radar Cross Section , RCS), although strongly, but in the other angular ranges it tends almost to zero. With a precise route planning , which takes the position of enemy radar systems into account, this effect can be optimally exploited to significantly reduce the overall radar cross-section of the machine. The US Air Force has not yet commented on the radar cross section of the B-2, but experts assume an RCS of 0.1 to 0.05 m².
The B-2 is supported by four F118-GE-110 - turbofan powered, also in modified form in the Lockheed U-2 are used. The F118 is essentially a derivative of the F101 series, but has a significantly higher bypass ratio , which lowers the temperature of the exhaust gases and thus also reduces the machine's infrared signature. For this reason there is no afterburner . The engine is controlled by a FADEC system, delivers up to 84.6 kN of thrust and has a specific consumption of 68.33 kg / kNh. The combustion chamber was the subject of intensive research and modifications, as contrails and high exhaust gas temperatures were to be prevented as much as possible. A Halon -based system is used to extinguish fire .
Due to its unusual design, the B-2 is an aircraft with negative static stability (also known as "aerodynamically unstable"). This means that it would be uncontrollable without permanent computer-generated control commands and would crash immediately. The B-2 therefore has a digital and quadruple redundant fly-by-wire system that interprets the pilot's inputs and uses them to generate the required control signals .
The AN / APQ-181, which was specially designed for use on the B-2, is used as on- board radar . It is essentially based on the AN / APG-70 of the F-15 Eagle , but has no air-to-air operating modes . However, through the combination of a passive phased array antenna and a relatively high operating frequency of 12 to 18 GHz, it generates above-average high-resolution SAR radar images. So that any radar emissions from the B-2 are not detected by hostile SIGINT systems, the APQ-181 has LPI properties. It also has around 20 other air-to-ground operating modes, such as GMTI or Terrain Avoidance (enables altitudes of around 60 meters above ground). The two antenna surfaces are located on the right and left under the cockpit area.
The avionics are controlled by 13 EMP -resistant MIL-STD-1750A computers, which are interconnected by 26 MIL-STD-1553 B data lines . The remaining systems are mostly networked by means of optical fibers . A SATCOM satellite connection is primarily used for communication , as it is more difficult to locate and works everywhere on earth. There is also a system for receiving messages on long wave frequencies. The navigation is based on an inertial and an astronomical system, whereby the latter can also be used during the day at high altitudes. Tactical Air Navigation is also supported.
The B-2 has a complex system for electronic warfare , the exact composition of which is largely subject to confidentiality. However, the advanced AN / APR-50 - radar warning system and the AN / AAR-54 - missile warning definitely a part of this complex.
Despite the complex systems and the demanding mission profile, two pilots are sufficient to operate the machine (for comparison: a B-52H requires at least five crew members), with one seat for an additional person. This is mainly due to the extensive use of modern computer systems, which carry out many work steps automatically and prepare the large amounts of information obtained for the pilots in a clear and easily interpretable way. The cockpit is equipped with a total of eight color multifunction displays that can show different information depending on the current situation, for example flight instruments , maps or weapon system information .
A chemical toilet , a mattress and a small kitchen niche are available to the crew for long periods of use, in extreme cases up to 35 hours . The pilots sit during the flight II ACES - ejection seats , wherein in case of an emergency exit before its triggering a portion of the cockpit roof is blown off.
Basic version. Can only use unguided Mk-84 bombs and free-falling nuclear weapons. Some parts of the avionics have not yet been implemented either. Deliveries began in December 1993 and ended after ten machines at the end of 1995.
This fully operational variant was delivered from 1996. Machines of this series have a GPS receiver and can therefore also use guided bombs from the JDAM series. The last of the eight machines was delivered in 1997. All “Block 10” models have also been brought up to date.
In 1997 two B-2s of this standard were delivered. Compared to the "Block 20" version, your radar has almost twice as many operating modes, the option of automatic terrain following flight ( terrain following radar ), improved defensive avionics, a laser- based system for the detection of contrails and a new weapon computer, which is much more Guns supported. The radar cross-section of the machine was significantly reduced (among other things by improved covers in the back area), whereby the complete removal of the surface and parts of the structure was necessary. All “Block 20” machines have been brought up to date.
Further increases in combat value
Even after the introduction of the “Block 30” modifications, the relatively small B-2 fleet received several additional combat value increases. These mostly related to the integration of new weapon systems such as the AGM-154 JSOW or the Paveway series. Integration programs for GBU-39 and MOP bombs are currently underway . In the area of communication, a MIDS terminal (supported inter alia. Link 16 ) and a new satellite communication system have been installed that can establish a connection to the new AEHF satellites. In addition, a new LPI data link ("Advanced Tactical Data Link") is to be implemented, which should enable communication with the F-22 and F-35 . The processors were also exchanged for newer models during the service period, such as the integration of PowerPC processors, new fiber optic cables and mass storage devices . In November 2002 Raytheon received the order to replace the passive phased array antennas with AESA models in order to increase the performance of the on-board radar. Each of the two antennas is said to have more than 2000 transmitters , with installation to be completed by 2011. The first appropriately modernized B-2 was delivered to the Air Force on March 17, 2009. In February 2008, Northrop Grumman received the order to modernize the avionics and the weapon computer so that the B-2 can also fight moving targets effectively.
With the development and proliferation of more and more powerful radar and air defense systems, it has become necessary in the course of time to further reduce the radar cross-section of the B-2 in order to cope with new threats. These measures are largely confidential, although it can be assumed that improvements were primarily made in the radar-absorbing materials and the aircraft surface, since the structure of the machine can no longer be fundamentally rebuilt at acceptable prices. It has become known, however, that the B-2 fleet is currently being fitted with a new radar-absorbing material that is primarily intended to simplify and shorten maintenance. The new substance is called “Alternate High Frequency Material” and should be applied to all existing B-2 bombers by 2012 [obsolete] as part of planned maintenance work.
|Wing area||≈ 490 m²|
|Empty mass||72,575 kg|
|maximum takeoff mass A1||152,635 kg|
|Tank capacity||111,291 liters (75,575 kg)|
|Service ceiling||15,152 m|
|drive||four General Electric F-118-GE-100 turbofan engines with 84.6 kN thrust each|
|number||active: 20; ANG : 0; Reserve: 0; Loss: 1|
In two internal weapon bays, up to 18,144 kg of weapons can be carried under normal conditions. Theoretically, up to 35,800 kg are possible, but such a high weapon load would greatly reduce the range, as about a third of the fuel would have to be dispensed with.
|nuclear||B61||16||320-540 kg||Max. 300 kt explosive force|
|B83||16||1090 kg||Max. 1.2 Mt explosive force|
|conventional||Mark 82||80||227 kg|
|Mark 84||16||908 kg|
|Water bomb||DST Mk 36||80||227 kg|
|Sea mine||Mark 62||80||227 kg||Ground mine with seismic
and magnetic sensors
|Cluster bomb||CBU-87||36||430 kg||202 EFPs|
|CBU-89||36||322 kg||72 anti-tank mines
22 anti-personnel mines
|CBU-97||36||420 kg||40 EFPs (autonomous destination search)|
|GPS steering||GBU-38 JDAM||80||227 kg|
|GBU-32 JDAM||16||454 kg|
|GBU-36||8th||908 kg||retrofitted Mk-84 bomb|
|GBU-37||8th||2041 kg||With BLU-113 warhead|
|EGBU-28||8th||≈ 2268 kg||based on the GBU-28|
|GBU-57 MOP||2||13,600 kg|
|Laser steering||GBU-27 Paveway III||8th||1065 kg|
|GBU-28 Paveway III||8th||2268 kg|
|Glide bomb||GBU-39 SDB||216||129 kg||Integration is ongoing|
|AGM-154 JSOW||16||≈ 475 kg|
|Cruise missiles||AGM-158 JASSM||16||1020 kg|
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