Development began under theAdvanced Technology Bomber (ATB) project during theCarter administration, which cancelled the Mach 2-capableB-1A bomber in part because the ATB showed such promise, but development difficulties delayed progress and drove up costs. Ultimately, the program produced 21 B-2s at an average cost of $2.13 billion each (~$4.17 billion in 2024 dollars), including development, engineering, testing, production, and procurement.[9] Building each aircraft cost an average of US$737 million,[9] while totalprocurement costs (including production,spare parts, equipment,retrofitting, and software support) averaged $929 million (~$1.14 billion in 2024 dollars) per plane.[9] Theproject's considerablecapital andoperating costs made it controversial in theU.S. Congress even before the winding down of theCold War dramatically reduced the desire for a stealth aircraft designed to strike deep in Soviet territory. Consequently, in the late 1980s and 1990s lawmakers shrank the planned purchase of 132 bombers to 21.
The B-2 can perform attack missions at altitudes of up to 50,000 feet (15,000 m); it has an unrefueled range of more than 6,000 nautical miles (11,000 km; 6,900 mi) and can fly more than 10,000 nautical miles (19,000 km; 12,000 mi) with onemidair refueling. It entered service in 1997 as the second aircraft designed with advanced stealth technology, after theLockheed F-117 Nighthawk attack aircraft. Primarily designed as a nuclear bomber, the B-2 was first used in combat to drop conventional, non-nuclearordnance in theKosovo War in 1999. It was later usedin Iraq,Afghanistan,Libya,Yemen, andIran.[10][11]
By the mid-1970s, military aircraft designers had learned of a new method to avoid missiles and interceptors, known today as "stealth". The concept was to build an aircraft with anairframe that deflected or absorbedradar signals so that little was reflected back to the radar unit. An aircraft having radar stealth characteristics would be able to fly nearly undetected and could be attacked only by weapons and systems not relying on radar. Although other detection measures existed, such as human observation,infrared scanners, andacoustic locators, their relatively short detection range or poorly developed technology allowed most aircraft to fly undetected, or at least untracked, especially at night.[16]
In 1974,DARPA requested information from U.S. aviation firms about the largestradar cross-section of an aircraft that would remain effectively invisible to radars.[17] Initially,Northrop andMcDonnell Douglas were selected for further development.Lockheed had experience in this field with the development of theLockheed A-12 andSR-71, which included several stealthy features, notably its canted vertical stabilizers, the use of composite materials in key locations, and the overall surface finish inradar-absorbing paint. A key improvement was the introduction of computer models used to predict the radar reflections from flat surfaces where collected data drove the design of a "faceted" aircraft. Development of the first such designs started in 1975 with theHave Blue, a model Lockheed built to test the concept.[18]
Plans were well advanced by the summer of 1975, when DARPA started the Experimental Survivability Testbed project. Northrop and Lockheed were awarded contracts in the first round of testing. Lockheed received the sole award for the second test round in April 1976 leading to theHave Blue program and eventually theF-117 stealth attack aircraft.[19] Northrop also had a classified technology demonstration aircraft, theTacit Blue in development in 1979 atArea 51. It developed stealth technology, LO (low observables),fly-by-wire, curved surfaces, composite materials,electronic intelligence, and Battlefield Surveillance Aircraft Experimental. The stealth technology developed from the program was later incorporated into other operational aircraft designs, including the B-2 stealth bomber.[20]
Advanced Technology Bomber program
By 1976, these programs had progressed to a position in which a long-range strategic stealth bomber appeared viable. U.S. presidentJimmy Carter became aware of these developments during 1977, and it appears to have been one of the major reasons the B-1 was canceled.[21] Further studies were ordered in early 1978, by which point theHave Blue platform had flown and proven the concepts. During the1980 U.S. presidential election campaign in 1979,Ronald Reagan repeatedly stated that Carter was weak on defense and used the B-1 as a prime example. In response, on 22 August 1980 theCarter administration publicly disclosed that theUnited States Department of Defense was working to develop stealth aircraft, including a bomber.[22]
The B-2's first public display in 1988 at Palmdale, California: in front of the B-2 is a star formed with five B-2 silhouettes
The Advanced Technology Bomber (ATB) program began in 1979.[23] Full development of theblack project followed, funded under the code name "Aurora".[24] After the evaluations of the companies' proposals, the ATB competition was narrowed to the Northrop/Boeing and Lockheed/Rockwell teams with each receiving a study contract for further work.[23] Both teams usedflying wing designs.[24] The Northrop proposal was code named "Senior Ice", and the Lockheed proposal code named "Senior Peg".[25] Northrop had experience developing flying wing aircraft: theYB-35 andYB-49.[26] The Northrop design was larger and had curved surfaces while the Lockheed design was faceted and included a small tail.[24] In 1979, designerHal Markarian produced a sketch of the aircraft that bore considerable similarities to the final design.[27] The United States Air Force (USAF) originally planned to procure 165 ATB bombers.[1]
The Northrop team's ATB design was selected over the Lockheed/Rockwell design on 20 October 1981.[23][28] The Northrop design received the designation B-2 and the name "Spirit". The bomber's design was changed in the mid-1980s when the mission profile was changed fromhigh-altitude to low-altitude, terrain-following. The redesign delayed the B-2's first flight by two years and added about US$1 billion to the program's cost.[22] By 1989, the U.S. had secretly spent an estimated US$23 billion onresearch and development for the B-2.[29]MIT engineers and scientists helped assess the mission effectiveness of the aircraft under a five-yearclassified contract during the 1980s.[30] ATB technology was also fed into theAdvanced Tactical Fighter program, which would produce theLockheed YF-22 andNorthrop YF-23, and later theLockheed Martin F-22. Northrop was the B-2's prime contractor; major subcontractors includedBoeing,Hughes Aircraft (nowRaytheon),General Electric Aviation, andVought Aircraft.[10]
Secrecy and espionage
The B-2's first publicized flight in 1989
During its design and development, the Northrop B-2 program was ablack project; all program personnel needed a secret clearance.[31] Still, it was less closely held than the Lockheed F-117 program; more people in the federal government knew about the B-2, and more information about the project was available. Both during development and in service, considerable effort has been devoted to maintaining the security of the B-2's design and technologies. Staff working on the B-2 in most, if not all, capacities need a level of special-access clearance and undergo extensive background checks carried out by a special branch of the USAF.[32]
A former Ford automobile assembly plant inPico Rivera, California, was acquired and substantially rebuilt; the plant's employees were sworn to secrecy. To avoid suspicion, components were typically purchased throughfront companies, military officials would visit out of uniform, staff members were routinely subjected topolygraph examinations, and the business unit was named the "Advanced Systems Division". Nearly all information on the program was kept from theGovernment Accountability Office (GAO) and members of Congress until the mid-1980s.[33]
The B-2 was first publicly displayed on 22 November 1988 atUSAF Plant 42 inPalmdale, California, where it was assembled. This viewing was heavily restricted, and guests were not allowed to see the rear of the B-2. However,Aviation Week editors found that there were no airspace restrictions above the presentation area and took aerial photographs of the aircraft's secret rear section[34] with suppressed engine exhausts.[6] The B-2's (s/n 82-1066 / AV-1) first public flight was on 17 July 1989 from Palmdale toEdwards Air Force Base.[34]
In 1984, Northrop employeeThomas Patrick Cavanagh was arrested for attempting to sell classified information from the Pico Rivera factory to theSoviet Union.[35] Cavanagh was sentenced to life in prison in 1985 but released on parole in 2001.[36] In October 2005,Noshir Gowadia, a design engineer who worked on the B-2's propulsion system, was arrested for selling classified information to China.[37] Gowadia was convicted and sentenced to 32 years in prison.[38]
Program costs and procurement
A procurement of 132 aircraft was planned in the mid-1980s but was later reduced to 75.[39] By the early 1990s theSoviet Union dissolved, effectively eliminating the Spirit's primaryCold War mission. Under budgetary pressures and U.S. Congressional opposition, in his 1992State of the Union address, PresidentGeorge H. W. Bush announced B-2 production would be limited to 20 aircraft.[40] In 1996, however, theClinton administration, though originally committed to ending production of the bombers at 20 aircraft, authorized the conversion of a 21st bomber, aprototype test model, to Block 30 fully operational status at a cost of nearly $500 million (~$920 million in 2024 dollars).[41] In 1995, Northrop made a proposal to the USAF to build 20 additional aircraft with aflyaway cost of $566 million each.[42]
The program was the subject of public controversy for its cost to American taxpayers. In 1996, the GAO disclosed that the USAF's B-2 bombers "will be, by far, the costliest bombers to operate on a per aircraft basis", costing over three times as much as theB-1B (US$9.6 million annually) and over four times as much as the B-52H (US$6.8 million annually). In September 1997, each hour of B-2 flight necessitated 119 hours of maintenance. Comparable maintenance needs for the B-52 and the B-1B are 53 and 60 hours, respectively, for each hour of flight. A key reason for this cost is the provision of air-conditioned hangars large enough for the bomber's 172 ft (52 m) wingspan, which are needed to maintain the aircraft's stealth properties, particularly its "low-observable" stealth skins.[43][44] Maintenance costs are about $3.4 million per month for each aircraft.[45] An August 1995 GAO report disclosed that the B-2 had trouble operating in heavy rain, as rain could damage the aircraft's stealth coating, causing procurement delays until an adequate protective coating could be found. In addition, the B-2's terrain-following/terrain-avoidance radar had difficulty distinguishing rain from other obstacles, rendering the subsystem inoperable during rain.[46] However a subsequent report in October 1996 noted that the USAF had made some progress in resolving the issues with the radar via software fixes and hoped to have these fixes undergoing tests by the spring of 1997.[47]
The total "military construction" cost related to the program was projected to be US$553.6 million in 1997 dollars. The cost to procure each B-2 was US$737 million in 1997 dollars (equivalent to US$1.334 billion in 2021)[48], based only on a fleet cost of US$15.48 billion.[9] The procurement cost per aircraft, as detailed in GAO reports, which include spare parts and software support, was $929 million per aircraft in 1997 dollars.[9]
The total program cost projected through 2004 was US$44.75 billion in 1997 dollars (equivalent to US$81 billion in 2021)[48]. This includes development, procurement, facilities, construction, and spare parts. The total program cost averaged US$2.13 billion per aircraft.[9] The B-2 may cost up to $135,000 per flight hour to operate in 2010, which is about twice that of the B-52 and B-1.[49][50]
Opposition
In its consideration of the fiscal year 1990 defense budget, the U.S. House of Representative Armed Services Committee trimmed $800 million from the B-2 research and development budget, while at the same time staving off a motion to end the project. Opposition in committee and in Congress was mostly broad and bipartisan, with CongressmenRon Dellums (D-CA),John Kasich (R-OH), andJohn G. Rowland (R-CT) authorizing the motion to end the project—as well as others in the Senate, includingJim Exon (D-NE) andJohn McCain (R-AZ) also opposing the project.[51] Dellums and Kasich, in particular, worked together from 1989 through the early 1990s to limit production to 21 aircraft and were ultimately successful.[52]
The escalating cost of the B-2 program and evidence of flaws in the aircraft's ability to elude detection by radar[51] were among factors that drove opposition to continue the program. At the peak production period specified in 1989, the schedule called for spending US$7 billion to $8 billion per year in 1989 dollars, something committee ChairLes Aspin (D-WI) said "won't fly financially".[53] In 1990, the Department of Defense accused Northrop of using faulty components in theflight control system; it was also found that redesign work was required to reduce the risk of damage to engine fan blades by bird ingestion.[54]
In time, several prominent members of Congress began to oppose the program's expansion, including SenatorJohn Kerry (D-MA), who cast votes against the B-2 in 1989, 1991, and 1992. By 1992, U.S. president Bush had called for the cancellation of the B-2 and promised to cut military spending by 30% in the wake of the collapse of the Soviet Union.[55] In October 1995, formerChief of Staff of the USAF,General Mike Ryan, and former chairman of the Joint Chiefs of Staff, GeneralJohn Shalikashvili, strongly recommended against Congressional action to fund the purchase of any additional B-2s, arguing that to do so would require unacceptable cuts in existing conventional and nuclear-capable aircraft,[56] and that the military had greater priorities in spending a limited budget.[57]
Some B-2 advocates argued that procuring twenty additional aircraft would save money because B-2s would be able to deeply penetrate anti-aircraft defenses and use low-cost, short-range attack weapons rather than expensive standoff weapons. However, in 1995, theCongressional Budget Office (CBO) and its Director of National Security Analysis found that additional B-2s would reduce the cost of expended munitions by less than US$2 billion in 1995 dollars during the first two weeks of a conflict, in which the USAF predicted bombers would make their greatest contribution; this was a small fraction of the US$26.8 billion (in 1995 dollars) life cycle cost that the CBO projected for an additional 20 B-2s.[58]
In 1997, asRanking Member of theU.S. House Armed Services Committee and National Security Committee, CongressmanRon Dellums (D-CA), a long-time opponent of the bomber, cited five independent studies and offered an amendment to that year's defense authorization bill to cap production of the bombers to the existing 21 aircraft; the amendment was narrowly defeated.[59] Nonetheless, Congress did not approve funding for additional B-2s.
Further developments
Several upgrade packages have been applied to the B-2. In July 2008, the B-2's onboard computing architecture was extensively redesigned; it now incorporates a new integratedprocessing unit that communicates with systems throughout the aircraft via a newly installedfiber optic network; a new version of the operational flight program software was also developed, withlegacy code converted from theJOVIAL programming language to standardC.[60][61] Updates were also made to the weapon control systems to enable strikes upon moving targets, such as ground vehicles.[62]
B-2 as viewed from below
On 29 December 2008, USAF officials awarded a US$468 million contract to Northrop Grumman to modernize the B-2 fleet's radars.[63] Changing the radar's frequency was required as theUnited States Department of Commerce had sold that radio spectrum to another operator.[64] In July 2009, it was reported that the B-2 had successfully passed a major USAF audit.[65] In 2010, it was made public that theAir Force Research Laboratory had developed a new material to be used on the part of the wing trailing edge subject to engine exhaust, replacing existing material that quickly degraded.[66]
In July 2010, political analyst Rebecca Grant speculated that when the B-2 becomes unable to reliably penetrate enemy defenses, theLockheed Martin F-35 Lightning II may take on its strike/interdiction mission, carryingB61 nuclear bombs as a tactical bomber.[67] However, in March 2012,The Pentagon announced that a $2 billion, 10-year-long modernization of the B-2 fleet was to begin. The main area of improvement would be replacement of outdated avionics and equipment.[68] Continued modernization efforts likely have continued in secret, as alluded to by a B-2 commander fromWhiteman Air Force Base in April 2021, possibly indicating offensive weapons capability against threatening air defenses and aircraft. He stated:
without getting into specifics, and without getting into things that we frankly just don't discuss in open channels, I will tell you that our current bomber fleet, and this is all of them, we use some pretty innovative ways to integrate modern weapons capabilities to have us both maintain and increase our survivability. And for the B-2 specifically, the expansion of some of our strike capabilities allow us to increase our survivability beyond the fighter escort realm. Now the B-2 fleet is continuing to do that technological advancement, and that's enabled us to expand our strike capabilities, as well. Although we've been around for over 30 years, there's a lot of life left in this platform, and up until the B-21 is well on the scene and doing its job, this aircraft will continue to be at the forefront of our country and our nation's defense... and with these, and continued innovative upgrades, and weapons system capabilities, we will continue to do that until the last jet flies off the ramp into retirement.[69]
It was reported in 2011 thatThe Pentagon was evaluating an unmanned stealth bomber, characterized as a "mini-B-2", as a potential replacement in the near future.[70] In 2012, USAF Chief of Staff GeneralNorton Schwartz stated the B-2's 1980s-era stealth technologies would make it less survivable in future contested airspaces, so the USAF is to proceed with theNext-Generation Bomber despite overall budget cuts.[71] In 2012 projections, it was estimated that the Next-Generation Bomber would have an overall cost of $55 billion.[72]
In 2013, the USAF contracted for the Defensive Management System Modernization (DMS-M) program to replace the antenna system and other electronics to increase the B-2's frequency awareness.[73] The Common Very Low Frequency Receiver upgrade allows the B-2s to use the samevery low frequency transmissions as theOhio-class submarines so as to continue in the nuclear mission until theMobile User Objective System is fielded.[citation needed] In 2014, the USAF outlined a series of upgrades including nuclear warfighting, a new integrated processing unit, the ability to carry cruise missiles, and threat warning improvements.[74] Due to ongoing software challenges, DMS-M was canceled by 2020, and the existing work was repurposed for cockpit upgrades.[75]
In 1998, a Congressional panel advised the USAF to refocus resources away from continued B-2 production and instead begin development of a new bomber, either a new build or a variant of the B-2. In its 1999 bomber roadmap the USAF eschewed the panel's recommendations, believing its current bomber fleet could be maintained until the 2030s. The service believed that development could begin in 2013, in time to replace aging B-2s, B-1s and B-52s around 2037.[76][77]
Although the USAF previously planned to operate the B-2 until 2058, the FY 2019 budget moved up its retirement to "no later than 2032". It also moved the retirement of the B-1 to 2036 while extending the B-52's service life into the 2050s, because the B-52 has lower maintenance costs, versatile conventional payload, and the ability to carry nuclearcruise missiles (which the B-1 is treaty-prohibited from doing). The decision to retire the B-2 early was made because the small fleet of 20 is considered too expensive per plane to retain, with its position as a stealth bomber being taken over with the introduction of theB-21 Raider starting in the mid-2020s.[15]
Design
Side view of a B-2 Spirit
Overview
The B-2 Spirit was developed to take over the USAF's vital penetration missions, allowing it to travel deep into enemy territory to deployordnance, which could includenuclear weapons.[78] The B-2 is aflying wing aircraft, meaning that it has no fuselage or tail.[78] It has significant advantages over previous bombers due to its blend of low-observable technologies with high aerodynamic efficiency and a large payload. Low observability provides greater freedom of action at high altitudes, thus increasing both range and field of view for onboard sensors. The USAF reports its range as about 6,000nautical miles (6,900 mi; 11,000 km).[10][79] At cruising altitude, the B-2refuels every six hours, taking on up to 50 short tons (45,000 kg) of fuel at a time.[80]
The development and construction of the B-2 required pioneering use ofcomputer-aided design andmanufacturing technologies due to its complex flight characteristics and design requirements to maintain very low visibility to multiple means of detection.[78][81] The B-2 bears a resemblance to earlier Northrop aircraft; theYB-35 andYB-49 were both flying wing bombers that had been canceled in development in the early 1950s,[82] allegedly for political reasons.[83] The resemblance goes as far as B-2 and YB-49 having the same wingspan.[84][85] The YB-49 also had a smallradar cross-section.[86][87]
About 80 pilots fly the B-2.[80] Each aircraft has a crew of two, a pilot in the left seat and mission commander in the right,[10] and has provisions for a third crew member if needed.[88] For comparison, the B-1B has a crew of four and the B-52 has a crew of five.[10] The B-2 is highly automated, and one crew member can sleep in acamp bed, use a toilet, or prepare a hot meal while the other monitors the aircraft, unlike most two-seat aircraft. Extensivesleep cycle andfatigue research was conducted to improve crew performance on long sorties.[80][89][90] Advanced training is conducted at theUSAF Weapons School.[91]
Armaments and equipment
A 2,000 lb (910 kg) BDU-56 bomb being loaded onto a bomb bay's rotary launcher, 2004
In the envisaged Cold War scenario, the B-2 was to perform deep-penetrating nuclear strike missions, making use of its stealth capabilities to avoid detection and interception throughout the missions.[92] 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.[93][94] The B-2 is capable of carrying 40,000 lb (18,000 kg) of ordnance.[10] Nuclear ordnance includes theB61 andB83 nuclear bombs; theAGM-129 ACM cruise missile was also intended for use on the B-2 platform.[94][95]
After the dissolution of the Soviet Union, it was decided to equip the B-2 for conventional precision attacks as well as for the strategic role of nuclear-strike.[92][96] The B-2 has a sophisticatedGPS-Aided Targeting System (GATS) that uses the aircraft'sAPQ-181synthetic aperture radar to map out targets before dropping GPS-aided bombs (GAMs)—later,Joint Direct Attack Munitions (JDAMs). In the B-2's original configuration, up to 16 GAMs or JDAMs could be deployed;[97] An upgrade in 2004 raised the carrier capacity to 80 JDAMs.[98]
To make the B-2 more effective than previous bombers, advanced and modernavionics were integrated into its design; these have been modified and improved to accommodate conventional-warfare missions. Thelow-probability-of-interceptAN/APQ-181 multi-mode radar is part of a digital navigation system that includesterrain-following radar andGlobal Positioning System (GPS) guidance, NAS-26astro-inertial navigation system (developed in the 1950s for the NorthropSM-62 Snark cruise missile)[104], and a Defensive Management System (DMS) to inform the flight crew of possible threats.[98] The DMS can automatically assess the detection capabilities of identified threats and indicated targets.[105] The DMS was to be upgraded by 2021 to detect radar emissions from air defenses, then feed the data to the auto-router so it can modify the mission route to minimize exposure to dangers.[106]
For safety and fault detection, an onboard test system is linked with most of the B-2’s avionics to monitor the performance and status of thousands of components and consumables; it also provides post-mission servicing instructions to ground crews.[107] In 2008, many of the 136[108] standalone distributed computers aboard the B-2, including the primary flight management computer, were being replaced by a single system.[109] The avionics are controlled by 13EMP-resistantMIL-STD-1750A computers connected through 26MIL-STD-1553B-buses; other system elements are connected viaoptical fiber.[110]
In addition to software upgrades and new radar-absorbent materials, the B-2 has had several major upgrades to its avionics and combat systems. For battlefield communications,Link-16 and a high-frequency satellite link have been installed. New munitions have been integrated. The AN/APQ-181 was given new antenna arrays to turn it into anactive electronically scanned array (AESA) radar,[111] and its operational frequency was changed to avoid interfering with other operators’ equipment.[98]
Becauseflying wing aircraft are inherently unstable, the B-2 uses a complex quadruplex computer-controlledfly-by-wire flight control system that can automatically manipulate flight surfaces and settings without direct pilot inputs to maintain aircraft stability.[112] The flight computer receives information on external conditions such as the aircraft's air speed and angle of attack viapitot-static sensing plates, as opposed to traditionalpitot tubes which would impair the aircraft's stealth capabilities.[113] The flight actuation system incorporates hydraulic and electrical servoactuated components, and it was designed with a high level of redundancy and fault-diagnostic capabilities.[114]
Northrop had investigated several means of applying directional control that would raise the aircraft's radar profile as little as possible, eventually settling on a combination of split brake-rudders and differential thrust.[105] Engine thrust became a key element of the B-2's aerodynamic design process early on; thrust not only affects drag and lift but pitching and rolling motions as well.[115] Four pairs of control surfaces are located along the wing's trailing edge; while most surfaces are used throughout the aircraft's flight envelope, the inner elevons are normally only in use at slow speeds, such as landing.[116] To avoid contact damage during takeoff and to provide a nose-down pitching attitude, all of the elevons remain drooped during takeoff until a high enough airspeed has been attained.[116]
Stealth
The B-2's engines are buried within its wing to conceal the engines' fans and minimize their exhaust signature.
To reduce optical visibility during daylight flights, the B-2 is painted in ananti-reflective paint.[94] The undersides are dark because it flies at high altitudes (50,000 ft (15,000 m)), and at that altitude a dark grey painting blends well into the sky. It is speculated to have an upward-facinglight sensor that alerts the pilot to increase or reduce altitude to match the changing illuminance of the sky.[117] The original design had tanks for acontrail-inhibiting chemical, but this was replaced in production aircraft by a contrail sensor that alerts the crew when they should change altitude.[118] The B-2 can be seen at ranges of 20 nmi (23 mi; 37 km) or less.[80] The B-2 is stored in a $5 million specialized air-conditioned hangar to maintain its stealth coating. Every seven years, this coating is carefully washed away with crystallized wheat starch so that the B-2's surfaces can be inspected for any dents or scratches.[119]
Radar
The B-2's low-dragflying wing configuration provides exceptional range and reduces its radar profile.[78][120] Reportedly, the B-2 has aradar cross-section (RCS) of about 0.1 m2 (1.1 sq ft).[121] The bomber does not always fly stealthily; when nearing air defenses pilots "stealth up" the B-2, a maneuver whose details are secret. The aircraft is stealthy, except briefly when the bomb bay opens. The flying wing design most closely resembles a so-called infinite flat plate (as vertical control surfaces dramatically increase RCS), the perfect stealth shape, as it would lack angles to reflect back radar waves (initially, the shape of the Northrop ATB concept was flatter; it gradually increased in volume according to specific military requirements).[122] Without vertical surfaces to reflect radar laterally, side aspect radar cross section is also reduced.[123] Radars operating at a lower frequency band (S or L band) are able to detect and track certain stealth aircraft that have multiple control surfaces, like canards or vertical stabilizers, where the frequency wavelength can exceed a certain threshold and cause a resonant effect.[124]
Illustration of the B-2's basic radar reflection angles
RCS reduction as a result of shape had already been observed on theRoyal Air Force'sAvro Vulcan strategic bomber,[125] and the USAF'sF-117 Nighthawk. The F-117 used flat surfaces (faceting technique) for controlling radar returns as during its development (seeLockheed Have Blue) in the early 1970s, technology only allowed for the simulation of radar reflections on simple, flat surfaces; computing advances in the 1980s made it possible to simulate radar returns on more complex curved surfaces.[126] The B-2 is composed of many curved and rounded surfaces across its exposed airframe to deflect radar beams. This technique, known ascontinuous curvature, was made possible by advances incomputational fluid dynamics, and first tested on theNorthrop Tacit Blue.[127][122]
Infrared
The gap below the air intake has the purpose of keeping theboundary layer out of the jet engine.
Some analysts claiminfra-red search and track systems (IRSTs) can detect stealth aircraft, because any aircraft surface heats up due to air friction. A two-channel IRST is a CO2 (4.3 μm absorption maxima) detection possible, through comparing between the low and high channel.[128][129]
According to theHuygens–Fresnel principle, even a very flat plate would still reflect radar waves, though much less than when a signal is bouncing at a right angle. Additional reduction in its radar signature was achieved by the use of variousradar-absorbent materials (RAM) to absorb and neutralize radar beams. The B-2 is mostly made of acarbon-graphitecomposite material that is stronger than steel, lighter than aluminum, and absorbs much radar energy.[82]
The B-2 is assembled with unusually tightengineering tolerances to avoid leaks of fluids as they could increase its radar signature.[89] Innovations such as alternatehigh frequency material (AHFM) and automated material application methods were also used to improve the aircraft's radar-absorbent properties and reduce maintenance requirements.[94][131] In early 2004, Northrop Grumman began applying a new AHFM to operational B-2s.[132] To protect its radar-absorbent material and coatings, each B-2 is kept inside a climate-controlled hangar (Extra Large Deployable Aircraft Hangar System) large enough to accommodate its 172-foot (52 m) wingspan.[133]
Shelter system
B-2s are supported by portable, environmentally-controlled hangars called B-2 Shelter Systems (B2SS).[134] The hangars are built by American Spaceframe Fabricators Incorporated and cost about US$5 million each.[134] The need for specialized hangars arose in 1998 when it was found that B-2s passing throughAndersen Air Force Base did not have the climate-controlled environment maintenance operations required.[134] In 2003, the B2SS program was managed by the Combat Support System Program Office atEglin Air Force Base.[134] B2SS hangars are known to have been deployed toNaval Support Facility Diego Garcia andRoyal Air Force Fairford.[134]
Operational history
A B-2 duringaerial refueling, which extends its range past 6,000 nautical miles (6,900 mi; 11,000 km) for intercontinental sorties
1990s
The first operational aircraft, christenedSpirit of Missouri, was delivered toWhiteman Air Force Base,Missouri, where the fleet is based, on 17 December 1993.[135] The B-2 reached initial operational capability (IOC) on 1 January 1997.[136] Depot maintenance for the B-2 is accomplished by USAF contractor support and managed atOklahoma City Air Logistics Center atTinker Air Force Base.[10] Originally designed to deliver nuclear weapons, modern usage has shifted towards a flexible role with conventional and nuclear capability.[94]
The B-2's combat debut was in 1999, during theKosovo War. It was responsible for destroying 33% of selected Yugoslav bombingtargets in the first eight weeks of U.S. involvement in the war.[10] During this war, six B-2s flew non-stop toYugoslavia from their home base in Missouri and back, totaling 30 hours. Although the bombers accounted for 50 sorties out of a total of 34,000 NATO sorties, they dropped 11 percent of all bombs.[137] The B-2 was the first aircraft to deploy GPS satellite-guidedJDAM "smart bombs" in combat use in Kosovo.[138] The use of JDAMs and precision-guided munitions effectively replaced the controversial tactic ofcarpet-bombing, which had been harshly criticized due to it causing indiscriminate civilian casualties in earlier conflicts, such as the 1991Gulf War.[139] On 7 May 1999, a B-2dropped five JDAMs on the Chinese Embassy[140] officially due to an error in targeting instructions, killing three people and injuring 20.[51] By then, the B-2 had dropped 500 bombs in Yugoslavia.[141]
2000s
The B-2 bombed ground targets at the beginning of theWar in Afghanistan (2001–2021) (Operation Crescent Wind/Operation Enduring Freedom). With aerial refueling support, the B-2 flew one of its longest missions to date from Whiteman Air Force Base in Missouri to Afghanistan and back.[10] B-2s would be stationed in the Middle East as a part of a US military buildup in the region from 2003.[142]
The B-2's combat use preceded a USAF declaration of "full operational capability" in December 2003.[10] The Pentagon's Operational Test and Evaluation 2003 Annual Report noted that the B-2's serviceability for Fiscal Year 2003 was still inadequate, mainly due to the maintainability of the B-2's low observable coatings. The evaluation also noted that the Defensive Avionics suite had shortcomings with "pop-up threats".[10][143]
During theIraq War, B-2s operated fromDiego Garcia and an undisclosed "forward operating location". Othersorties in Iraq have launched from Whiteman Air Force Base.[10] As of September 2013[update] the longest combat mission has been 44.3 hours.[80] "Forward operating locations" have been previously designated asAndersen Air Force Base inGuam andRAF Fairford in the United Kingdom, where new climate controlled hangars have been constructed. B-2s have conducted 27 sorties from Whiteman Air Force Base and 22 sorties from a forward operating location, releasing more than 1,500,000 pounds (680,000 kg) of munitions,[10] including 583 JDAM "smart bombs" in 2003.[98]
2010s
TheSpirit of Missouri at theDyess Air Force Base air show in 2018. This view depicts the body's two dimensional and seamless design, a distinct feature for evading radar detection.
In March 2011, B-2s were the first U.S. aircraft placed into action inOperation Odyssey Dawn, the UN mandated enforcement of theLibyan no-fly zone. Three B-2s dropped 40 bombs on a Libyan airfield in support of the UN no-fly zone.[148] The B-2s flew directly from the U.S. mainland across the Atlantic Ocean to Libya; each B-2 was refueled by allied tanker aircraft four times during each round trip mission.[149][150]
In August 2011,The New Yorker reported that prior to the May 2011 U.S. Special Operations raid intoAbbottabad,Pakistan that resulted in thedeath of Osama bin Laden, U.S. officials had considered an airstrike by one or more B-2s as an alternative; the use of abunker busting bomb was rejected due to potential damage to nearby civilian buildings.[151] There were also concerns an airstrike would make it difficult to positively identify bin Laden's remains, making it hard to confirm his death.[152]
On 28 March 2013, two B-2s flew a round trip of 13,000 miles (21,000 km) from Whiteman Air Force Base in Missouri to South Korea, dropping dummy ordnance on the Jik Do target range. The mission, part of the annual South Korean–U.S. military exercises, was the first time that B-2s flew over the Korean Peninsula. Tensions between the Koreas were high; North Korea protested the B-2's participation and threatened retaliatory nuclear strikes against South Korea and the United States.[153][154]
On 18 January 2017, two B-2s attacked anISIS training camp 19 miles (30 km) southwest ofSirte, Libya, killing about 85 militants. The B-2s together dropped 108 500-pound (230 kg) precision-guidedJoint Direct Attack Munition (JDAM) bombs. These strikes were followed by anMQ-9 Reaper unmanned aerial vehicle firingHellfire missiles. Each B-2 flew a 33-hour, round-trip mission from Whiteman Air Force Base with four or five (accounts differ) refuelings during the trip.[155][156]
2020s
On 16 October 2024, B-2As struck five underground weapons storage facilities inYemen as part of the campaign against theHouthis for attacking international shipping during theRed Sea crisis.[11] It was believed the strikes also served as a warning toIran, demonstrating the stealth bomber's ability to destroy underground targets.[157][158]RAAF Base Tindal in theNorthern Territory, Australia, was used as a staging ground for the strikes.[159]
In a 1994live fire exercise nearPoint Mugu, California, a B-2 drops 47 individual 500 lb (230 kg)Mark 82 bombs, which is more than half of a B-2's total ordnance payload.
On 23 February 2008, B-2 "AV-12"Spirit of Kansascrashed on the runway shortly after takeoff fromAndersen Air Force Base inGuam.[163]Spirit of Kansas had been operated by the393rd Bomb Squadron,509th Bomb Wing,Whiteman Air Force Base, Missouri, and had logged 5,176 flight hours. The two-person crew ejected safely from the aircraft. The aircraft was destroyed, ahull loss valued at US$1.4 billion.[164][165] After the accident, the USAF took the B-2 fleet off operational status for 53 days, returning on 15 April 2008.[166] The cause of the crash was later determined to be moisture in the aircraft's Port Transducer Units during air data calibration, which distorted the information being sent to the bomber's air data system. As a result, the flight control computers calculated an inaccurate airspeed, and a negative angle of attack, causing the aircraft to pitch upward 30 degrees during takeoff.[167] This was the first crash and loss of a B-2.
In February 2010, a serious incident involving a B-2 occurred at Andersen Air Force Base in Guam. The aircraft involved was AV-11Spirit of Washington. The aircraft was severely damaged by fire while on the ground and underwent 18 months of repairs to enable it to fly back to the mainland U.S. for more comprehensive repairs.[168][169]Spirit of Washington was repaired and returned to service in December 2013.[170][171] At the time of the accident, the USAF had no training to deal with tailpipe fires on the B-2s.[172]
On the night of 13–14 September 2021, B-2Spirit of Georgia made an emergency landing at Whiteman Air Force Base. The aircraft landed andwent off the runway into the grass and came to rest on its left side.[173] The cause was later determined to be faulty landing gear springs and "microcracking" in hydraulic connections on the aircraft. The lock link springs in the left landing gear had likely not been replaced in at least a decade, and produced about 11% less tension than specified. The "microcracking" reduced hydraulic support to the landing gear. These problems caused the landing gear to fold upon landing. The accident resulted in a minimum of $10.1 million in repair damages, but the final repair cost was still being determined in March 2022.[174][175]
On 10 December 2022, an in-flight malfunction aboard B-2 AV-16Spirit of Hawaii forced an emergency crash landing at Whiteman Air Force Base.[176] No personnel, including the flight crew, sustained injuries during the incident; there was a post-crash fire that was quickly put out.[177] Subsequently, all B-2s were grounded.[178] On 18 May 2023, Air Force officials lifted the grounding without disclosing any details about what caused the incident, or what steps had been taken to return the aircraft to operation.[179] In May 2024, the Air Force announced the B-2 would be divested, as it had been deemed to be "uneconomical to repair." Although no cost estimate was provided, the decision was likely influenced by the coming introduction of the B-21 bomber; after the B-2 crash in 2010, it took almost four years and over $100 million to return the aircraft to service because not losing one of the few penetrating bombers in the inventory was considered necessary to justify the effort. However, the impending arrival of the B-21 and coming retirement of the B-2 sometime after 2029 likely made USAF leaders decide it would not be worth the expense to repair it, only for it to soon be retired.[12][180][failed verification]
No operational B-2s have been retired by the Air Force to be put on display. B-2s have made occasional appearances on ground display at variousair shows.
B-2 test article (s/n AT-1000), the second of two built without engines or instruments and used for static testing, was placed on display in 2004 at theNational Museum of the United States Air Force nearDayton, Ohio.[181] The test article passed all structural testing requirements before the airframe failed.[181] The museum's restoration team spent over a year reassembling the fractured airframe. The display airframe is marked to resembleSpirit of Ohio (S/N 82-1070), the B-2 used to test the design's ability to withstand extreme heat and cold.[181] The exhibit featuresSpirit of Ohio's nose wheel door, with itsFire and Ice artwork, which was painted and signed by the technicians who performed the temperature testing.[181] The restored test aircraft is on display in the museum's "Cold War Gallery".[182]
Specifications (B-2A Block 30)
Orthographically projected diagram of the B-2 SpiritA B-2 in formation flight with eight U.S. NavyF/A-18 Hornets andSuper Hornets
2 internal bays for ordnance and payload with an official limit of 40,000 lb (18,000 kg).[79] In its operational history, the maximum ordnance payload is 60,000 lb (27,000 kg). Ordnance options carried include:
80× 500 lb (230 kg) class bombs (Mk-82,GBU-38) mounted on Bomb Rack Assembly (BRA)
36× 750 lb (340 kg) CBU class bombs on BRA
16× 2,000 lb (910 kg) class bombs (Mk-84,GBU-31) mounted on Rotary Launcher Assembly (RLA)
16×B61 orB83 nuclear bombs on RLA (strategic mission)
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