Northrop Grumman B-2 Spirit | Wikipedia audio article

The 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 flying wing design with a crew of two. The bomber can deploy both conventional
and thermonuclear weapons, such as up to eighty 500-pound class (230 kg) Mk 82 JDAM Global
Positioning System-guided bombs, or sixteen 2,400-pound (1,100 kg) B83 nuclear bombs.
The B-2 is the only acknowledged aircraft that can carry large air-to-surface standoff
weapons in a stealth configuration. Development started under the “Advanced Technology
Bomber” (ATB) project during the Carter administration; its expected performance was one of the President’s
reasons for the cancellation of the Mach 2 capable B-1A bomber. The ATB project continued
during the Reagan administration, but worries about delays in its introduction led to the
reinstatement of the B-1 program. Program costs rose throughout development. Designed
and manufactured by Northrop, later Northrop Grumman, the cost of each aircraft averaged
US$737 million (in 1997 dollars). Total procurement costs averaged $929 million per aircraft,
which includes spare parts, equipment, retrofitting, and software support. The total program cost,
which included 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 U.S. Congress. 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 1990s, 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. Twenty B-2s are in service
with the United States Air Force, which plans to operate them until 2032.The B-2 is capable
of all-altitude attack missions up to 50,000 feet (15,000 m), with a range of more than
6,000 nautical miles (6,900 mi; 11,000 km) on internal fuel and over 10,000 nautical
miles (12,000 mi; 19,000 km) with one midair refueling. It entered service in 1997 as the
second aircraft designed to have advanced stealth technology after the Lockheed F-117
Nighthawk attack aircraft. Though designed originally as primarily a nuclear bomber,
the B-2 was first used in combat dropping conventional, non-nuclear ordnance in the
Kosovo War in 1999. It later served in Iraq, Afghanistan, and Libya.==Development=====Origins===
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
an airframe that deflected or absorbed radar 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,
acoustic locators, their relatively short detection range or poorly-developed technology
allowed most aircraft to fly undetected, or at least untracked, especially at night.In
1974, DARPA requested information from U.S. aviation firms about the largest radar cross-section
of an aircraft that would remain effectively invisible to radars. Initially, Northrop and
McDonnell Douglas were selected for further development. Lockheed had experience in this
field due to developing the Lockheed A-12 and SR-71, which included a number of stealthy
features, notably its canted vertical stabilizers, the use of composite materials in key locations,
and the overall surface finish in radar-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 “the Hopeless Diamond”, a model Lockheed built to test the concept.Plans were
well advanced by the summer of 1975, when DARPA started the Experimental Survivability
Testbed (XST) 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 the Have Blue program and eventually the F-117 stealth attack aircraft. Northrop also
had a classified technology demonstration aircraft, the Tacit Blue in development in
1979 at Area 51. It developed stealth technology, LO (low observables), fly-by-wire, curved
surfaces, composite materials, electronic intelligence (ELINT), and Battlefield Surveillance
Aircraft Experimental (BSAX). “The stealth technology developed from the program was
later incorporated into other operational aircraft designs, including the B-2 stealth
bomber”.===ATB program===
By 1976, these programs had progressed to a position in which a long-range strategic
stealth bomber appeared viable. President Carter became aware of these developments
during 1977, and it appears to have been one of the major reasons the B-1 was canceled.
Further studies were ordered in early 1978, by which point the Have Blue platform had
flown and proven the concepts. During the 1980 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 the Carter administration publicly disclosed
that the United States Department of Defense was working to develop stealth aircraft, including
a bomber. The Advanced Technology Bomber (ATB) program
began in 1979. Full development of the black project followed, and was funded under the
code name “Aurora”. 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. Both teams used flying wing designs. The Northrop proposal was code named
“Senior Ice” and the Lockheed proposal code named “Senior Peg”. Northrop had prior experience
developing the YB-35 and YB-49 flying wing aircraft. The Northrop design was larger while
the Lockheed design included a small tail. In 1979, designer Hal Markarian produced a
sketch of the aircraft, that bore considerable similarities to the final design. The Air
Force originally planned to procure 165 of the ATB bomber.The Northrop team’s ATB design
was selected over the Lockheed/Rockwell design on 20 October 1981. 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 from high-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. An estimated US$23 billion was secretly spent for research and
development on the B-2 by 1989. MIT engineers and scientists helped assess the mission effectiveness
of the aircraft under a five-year classified contract during the 1980s.===Secrecy and espionage===During its design and development, the Northrop
B-2 program was a gray project before its revelation to the public. Unlike the Lockheed
F-117 program, which was a black project, the type of military project of which very
few people knew even existed while it was being designed and developed, more people
within the United States 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 have to achieve a level of special-access
clearance, and undergo extensive background checks carried out by a special branch of
the Air Force.For the manufacturing, a former Ford automobile assembly plant in Pico Rivera,
California, was acquired and heavily rebuilt; the plant’s employees were sworn to complete
secrecy regarding their work. To avoid the possibility of suspicion, components were
typically purchased through front companies, military officials would visit out of uniform,
and staff members were routinely subjected to polygraph examinations. The secrecy extended
so far that access to nearly all information on the program by both Government Accountability
Office (GAO) and virtually all members of Congress itself was severely limited until
the mid-1980s. Northrop (now Northrop Grumman) was the B-2’s prime contractor; major subcontractors
included Boeing, Hughes Aircraft (now Raytheon), GE, and Vought Aircraft.In 1984, a Northrop
employee, Thomas Cavanaugh was arrested for attempting to sell classified information
to the Soviet Union; the information was taken from Northrop’s Pico Rivera, California factory.
Cavanaugh was eventually sentenced to life in prison and released on parole in 2001.
The B-2 was first publicly displayed on 22 November 1988 at United States Air Force Plant
42 in Palmdale, 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 then-secret rear section with suppressed engine exhausts. The B-2’s
(s/n 82-1066 / AV-1) first public flight was on 17 July 1989 from Palmdale to Edwards AFB.In
October 2005, Noshir Gowadia, a design engineer who worked on the B-2’s propulsion system,
was arrested for selling B-2 related classified information to foreign countries. Gowadia
was convicted and sentenced to 32 years in prison for his actions.===Program costs and procurement===
A procurement of 132 aircraft was planned in the mid-1980s, but was later reduced to
75. By the early 1990s, the Soviet Union dissolved, effectively eliminating the Spirit’s primary
Cold War mission. Under budgetary pressures and Congressional opposition, in his 1992
State of the Union Address, President George H. W. Bush announced B-2 production would
be limited to 20 aircraft. In 1996, however, the Clinton administration, though originally
committed to ending production of the bombers at 20 aircraft, authorized the conversion
of a 21st bomber, a prototype test model, to Block 30 fully operational status at a
cost of nearly $500 million.In 1995, Northrop made a proposal to the USAF to build 20 additional
aircraft with a flyaway cost of $566 million each.The program was the subject of public
controversy for its cost to American taxpayers. In 1996, the General Accounting Office (GAO)
disclosed that the USAF’s B-2 bombers “will be, by far, the most costly bombers to operate
on a per aircraft basis”, costing over three times as much as the B-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 in turn. 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 stealthy properties, particularly its “low-observable” stealthy skins. Maintenance
costs are about $3.4 million a month for each aircraft.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, based only on a fleet cost
of US$15.48 billion. 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.The
total program cost projected through 2004 was US$44.75 billion in 1997 dollars. This
includes development, procurement, facilities, construction, and spare parts. The total program
cost averaged US$2.13 billion per aircraft. 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.===Opposition===
In its consideration of the fiscal year 1990 defense budget, the House 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 Congressmen Ron Dellums (D-CA), John Kasich (R-OH), and
John G. Rowland (R-CT) authorizing the motion to end the project—as well as others in
the Senate, including Jim Exon (D-NE) and John McCain (R-AZ) also opposing the project.The
escalating cost of the B-2 program and evidence of flaws in the aircraft’s ability to elude
detection by radar 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 Chair Les Aspin (D-WI)
said “won’t fly financially”. In 1990, the Department of Defense accused Northrop of
using faulty components in the flight control system; it was also found that redesign work
was required to reduce the risk of damage to engine fan blades by bird ingestion.In
time, a number of prominent members of Congress began to oppose the program’s expansion, including
later Democratic presidential nominee John Kerry, who cast votes against the B-2 in 1989,
1991 and 1992 while a U.S. Senator, representing Massachusetts. By 1992, Republican President
George H. W. Bush 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. In October 1995, former Chief
of Staff of the United States Air Force, General Mike Ryan, and former Chairman of the Joint
Chiefs of Staff, General John 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, and that the
military had greater priorities in spending a limited budget.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, the Congressional 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 Air Force predicted bombers would make their greatest
contribution; 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.In 1997, as Ranking Member of the House
Armed Services Committee and National Security Committee, Congressman Ron 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. Nonetheless, Congress did not approve funding
for additional B-2s.===
Further developments===A number of 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 integrated processing unit (IPU) that communicates with systems
throughout the aircraft via a newly installed fiber optic network; a new version of the
operational flight program software was also developed, with legacy code converted from
the JOVIAL programming language to standard C. Updates were also made to the weapon control
systems to enable strikes upon moving targets, such as ground vehicles. On 29 December 2008, Air Force officials awarded
a US$468 million contract to Northrop Grumman to modernize the B-2 fleet’s radars. Changing
the radar’s frequency was required as the United States Department of Commerce had sold
that radio spectrum to another operator. In July 2009, it was reported that the B-2 had
successfully passed a major USAF audit. In 2010, it was made public that the Air 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.In
July 2010, political analyst Rebecca Grant speculated that when the B-2 becomes unable
to reliably penetrate enemy defenses, the Lockheed Martin F-35 Lightning II may take
on its strike/interdiction mission, carrying B61 nuclear bombs as a tactical bomber. 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.It was reported in 2011 that the Pentagon was evaluating an unmanned
stealth bomber, characterized as a “mini-B-2”, as a potential replacement in the near future.
In 2012, Air Force Chief of Staff General Norton 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 the Next-Generation Bomber despite overall budget cuts. In 2012 projections,
it was estimated that the Next-Generation Bomber would have an overall cost of $55 billion.In
2013, the USAF contracted for the Defensive Management System Modernization program to
replace the antenna system and other electronics to increase the B-2’s frequency awareness.
The Common Very Low Frequency Receiver upgrade will allow the B-2s to use the same very low
frequency transmissions as the Ohio-class submarines so as to continue in the nuclear
mission until the Mobile User Objective System is fielded. 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.Although the Air Force previously
planned to operate the B-2 to 2058, their FY 2019 budget moved up its retirement to
“no later than 2032”. It also moved retirement of the B-1 to 2036 while extending the B-52’s
service life into the 2050s, due to the latter’s lower maintenance costs, versatile conventional
payload, and ability to carry nuclear cruise 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 the B-21 Raider starting in the mid-2020s.==Design=====Overview===
The B-2 Spirit was developed to take over the USAF’s vital penetration missions, able
to travel deep into enemy territory to deploy ordnance which could include nuclear weapons.
The B-2 is a flying wing aircraft, meaning that it has no fuselage or tail. It has significant
advantages over previous bombers due to its blend of low-observable technologies with
high aerodynamic efficiency and large payload. Low observability provides a greater freedom
of action at high altitudes, thus increasing both range 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 (45,000
kg) of fuel at a time.The development and construction of the B-2 required pioneering
use of computer-aided design and manufacturing technologies, due to its complex flight characteristics
and design requirements to maintain very low visibility to multiple means of detection.
The B-2 bears a resemblance to earlier Northrop aircraft; the YB-35 and YB-49 were both 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. The YB-49
also had a small radar cross-section.Approximately 80 pilots fly the B-2. Each aircraft has a
crew of two, a pilot in the left seat and mission 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 one crew member can sleep in a camp bed,
use a toilet, or prepare a hot meal while the other monitors the aircraft, unlike most
two-seat aircraft. Extensive sleep cycle and fatigue research was conducted to improve
crew performance on long sorties. Advanced training is conducted at the USAF Weapons
School.===Armaments and equipment===The B-2, in the envisaged Cold War scenario,
was to perform deep-penetrating nuclear strike missions, making use of its stealthy capabilities
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 is capable of carrying 40,000 lb (18,000 kg) 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 as well as for the strategic
role of nuclear-strike. The B-2 features a sophisticated GPS-Aided Targeting System (GATS)
that uses the aircraft’s 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
(JDAM). In the B-2’s 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 mines, 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-2’s bomb bays with one per bay, 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
capability for the first time.===Avionics and systems===
In 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 probability
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 Defensive 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. The DMS will be upgraded by 2021 to detect
radar emissions from air defenses to allow changes to the auto-router’s mission planning
information while in-flight so it can receive new data quickly to plan a route that minimizes
exposure to dangers. For safety and fault-detection purposes, an
on-board test system is linked with the majority 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 management 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
the 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 undertaken, and the AN/APQ-181 radar’s 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. Due to the B-2’s composite structure, it is
required to stay 40 miles (64 km) away from thunderstorms, to avoid static discharge and
lightning strikes.===Flight controls===In order to address the inherent flight instability
of a flying wing aircraft, the B-2 uses a complex quadruplex 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 aircraft’s current air speed and angle of attack via
pitot-static sensing plates, as opposed to traditional pitot tubes which would impair
the aircraft’s 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.Northrop had investigated several means of applying
directional control that would infringe on the aircraft’s radar profile as little as
possible, eventually settling on a combination of split brake-rudders and differential thrust.
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. 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. To avoid potential 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.===Stealth===The B-2’s low-observable, or “stealth”, characteristics
enable the undetected penetration of sophisticated anti-aircraft defenses and to attack even
heavily defended targets. This stealth comes from a combination of reduced acoustic, infrared,
visual and radar signatures (multi-spectral camouflage) to evade the various detection
systems that could be used to detect and be used to direct attacks against an aircraft.
The B-2’s stealth enables the reduction of supporting aircraft that are required to provide
air cover, Suppression of Enemy Air Defenses and electronic countermeasures, making the
bomber a “force multiplier”. As of September 2013, there have been no instances of a missile
being launched at a B-2.To reduce optical visibility during daylight flights, the B-2
is painted in an anti-reflective paint. 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-facing light sensor which alerts the
pilot to increase or reduce altitude to match the changing illuminance of the sky. The original
design had tanks for a contrail-inhibiting chemical, but this was replaced in production
aircraft by a contrail sensor that alerts the crew when they should change altitude.
The B-2 is vulnerable to visual interception at ranges of 20 nmi (23 mi; 37 km) or less.====Radar====
Reportedly, the B-2 has a radar cross-section (RCS) of about 0.1 m2 (1.1 sq ft). 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 B-2’s clean, low-drag flying wing configuration not only provides exceptional
range but is also beneficial to reducing its radar profile. 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). Without vertical surfaces to reflect radar
laterally, side aspect radar cross section is also reduced. 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. RCS reduction as a result of shape had already
been observed on the Royal Air Force’s Avro Vulcan strategic bomber, and the USAF’s F-117
Nighthawk. The F-117 used flat surfaces (faceting technique) for controlling radar returns as
during its development (see Lockheed 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.
The B-2 is composed of many curved and rounded surfaces across its exposed airframe to deflect
radar beams. This technique, known as continuous curvature, was made possible by advances in
computational fluid dynamics, and first tested on the Northrop Tacit Blue.====Infrared====Some analysts claim infra-red search and track
systems (IRSTs) can be deployed against stealth aircraft, because any aircraft surface heats
up due to air friction and with a two channel IRST is a CO2 (4.3 µm absorption maxima)
detection possible, through difference comparing between the low and high channel.Burying engines
deep inside the fuselage also minimizes the thermal visibility or infrared signature of
the exhaust. At the engine intake, cold air from the boundary layer below the main inlet
enters the fuselage (boundary layer suction, first tested on the Northrop X-21) and is
mixed with hot exhaust air just before the nozzles (similar to the Ryan AQM-91 Firefly).
According to the Stefan–Boltzmann law, this results in less energy (thermal radiation
in the infrared spectrum) being released and thus a reduced heat signature. The resulting
cooler air is conducted over a surface composed of heat resistant carbon-fiber-reinforced
polymer and titanium alloy elements, which disperse the air laterally, in order to accelerate
its cooling. The B-2 lacks afterburners as the hot exhaust would increase the infrared
footprint; breaking the sound barrier would produce an obvious sonic boom as well as aerodynamic
heating of the aircraft skin which would also increase the infrared footprint.====Materials====
According to the Huygens–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 various radar-absorbent materials
(RAM) to absorb and neutralize radar beams. The majority of the B-2 is made out of a carbon-graphite
composite material that is stronger than steel, lighter than aluminum, and absorbs a significant
amount of radar energy.The B-2 is assembled with unusually tight engineering tolerances
to avoid leaks as they could increase its radar signature. Innovations such as alternate
high frequency material (AHFM) and automated material application methods were also incorporated
to improve the aircraft’s radar-absorbent properties and reduce maintenance requirements.
In early 2004, Northrop Grumman began applying a newly developed AHFM to operational B-2s.
In order to protect the operational integrity of its sophisticated 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.====Shelter system====
B-2s are supported by portable, environmentally-controlled hangars called B-2 Shelter Systems (B2SS).
The hangars are built by American Spaceframe Fabricators Inc. and cost approximately US$5
million apiece. The need for specialized hangars arose in 1998 when it was found that B-2s
passing through Andersen Air Force Base did not have the climate-controlled environment
maintenance operations required. In 2003, the B2SS program was managed by the Combat
Support System Program Office at Eglin Air Force Base. B2SS hangars are known to have
been deployed to Naval Support Facility Diego Garcia and RAF Fairford.==Operational history==The first operational aircraft, christened
Spirit of Missouri, was delivered to Whiteman Air Force Base, Missouri, where the fleet
is based, on 17 December 1993. The B-2 reached initial operational capability (IOC) on 1
January 1997. Depot maintenance for the B-2 is accomplished by U.S. Air Force contractor
support and managed at Oklahoma City Air Logistics Center at Tinker Air Force Base. Originally
designed to deliver nuclear weapons, modern usage has shifted towards a flexible role
with conventional and nuclear capability.The B-2’s combat debut was in 1999, during the
Kosovo War. It was responsible for destroying 33% of selected Serbian bombing targets in
the first eight weeks of U.S. involvement in the War. During this war, six B-2s flew
non-stop to Kosovo from their home base in Missouri and back, totaling 30 hours. Although
the bombers accounted 50 sorties out of a total of 34,000 NATO sorties, they dropped
11 percent of all bombs. The B-2 was the first aircraft to deploy GPS satellite-guided JDAM
“smart bombs” in combat use in Kosovo. The use of JDAMs and precision-guided munitions
effectively replaced the controversial tactic of carpet-bombing, which had been harshly
criticized due to it causing indiscriminate civilian casualties in prior conflicts, such
as the 1991 Gulf War. On 7 May 1999, a B-2 dropped five JDAMs on the Chinese Embassy,
killing several staff. By then, the B-2 had dropped 500 bombs in Kosovo.The B-2 saw service
in Afghanistan, striking ground targets in support of Operation Enduring Freedom. With
aerial refueling support, the B-2 flew one of its longest missions to date from Whiteman
Air Force Base, Missouri to Afghanistan and back. B-2s would be stationed in the Middle
East as a part of a US military buildup in the region from 2003.The B-2’s combat use
preceded a U.S. Air Force declaration of “full operational capability” in December 2003.
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”. During the Iraq War (Operation Iraqi Freedom),
B-2s operated from Diego Garcia and an undisclosed “forward operating location”. Other sorties
in Iraq have launched from Whiteman AFB. As of September 2013 the longest combat mission
has been 44.3 hours. “Forward operating locations” have been previously designated as Andersen
Air Force Base in Guam and RAF Fairford in the United Kingdom, where new climate controlled
hangars have been constructed. B-2s have conducted 27 sorties from Whiteman AFB and 22 sorties
from a forward operating location, releasing more than 1,500,000 pounds (680,000 kg) of
munitions, including 583 JDAM “smart bombs” in 2003.In response to organizational issues
and high-profile mistakes made within the Air Force, all of the B-2s, along with the
nuclear-capable B-52s and the Air Force’s intercontinental ballistic missiles (ICBMs),
were transferred to the newly formed Air Force Global Strike Command on 1 February 2010.In
March 2011, B-2s were the first U.S. aircraft into action in Operation Odyssey Dawn, the
UN mandated enforcement of the Libyan no-fly zone. Three B-2s dropped 40 bombs on a Libyan
airfield in support of the UN no-fly zone. The B-2s flew directly from the U.S. mainland
across the Atlantic Ocean to Libya; a B-2 was refueled by allied tanker aircraft four
times during each round trip mission.In August 2011, The New Yorker reported that prior to
the May 2011 U.S. Special Operations raid into Abbottabad, Pakistan that resulted in
the death of Osama bin Laden, U.S. officials had considered an airstrike by one or more
B-2s as an alternative; an airstrike was rejected because of damage to civilian buildings in
the area from using a bunker busting bomb. There were also concerns an airstrike would
make it difficult to positively identify Bin Laden’s remains and so confirming his death
would be difficult.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–United States
military exercises, was the first time that B-2s overflew the Korean peninsula. Tensions
between North and South Korea were high during; after the exercise North Korea protested against
the participation of the B-2s and made threats of retaliatory nuclear strikes against South
Korea and the United States.On 18 January 2017, two B-2s attacked an ISIS training camp
19 miles (30 km) southwest of Sirte, Libya, killing around 85 militants. The B-2s together
dropped 108 500-pound precision-guided Joint Direct Attack Munition (JDAM) bombs. These
strikes were followed by an MQ-9 Reaper unmanned aerial vehicle firing Hellfire missiles. Each
B-2 flew a 34-hour, round-trip mission from Whiteman Air Force Base, Missouri with 15
refuelings during the trip.==Operators==United States Air Force (20 aircraft in active
inventory) Air Force Global Strike Command509th Bomb
Wing – Whiteman Air Force Base, Missouri (currently has 19 B-2s)13th Bomb Squadron
2005–present 325th Bomb Squadron 1998–2005
393d Bomb Squadron 1993–present 394th Combat Training Squadron 1996–2018
Air Combat Command53d Wing – Eglin Air Force Base, Florida72d Test and Evaluation Squadron
(Whiteman AFB, Missouri) 1998–present57th Wing – Nellis AFB, Nevada325th Weapons Squadron
– Whiteman AFB, Missouri 2005–present 715th Weapons Squadron 2003–2005
Air National Guard131st Bomb Wing (Associate) – Whiteman AFB, Missouri 2009–present110th
Bomb Squadron Air Force Materiel Command412th Test Wing
– Edwards Air Force Base, California (has one B-2)419th Flight Test Squadron 1997–present
420th Flight Test Squadron 1992–1997 Air Force Systems Command6510th Test Wing
– Edwards AFB, California 1989–19926520th Flight Test Squadron==
Accidents==On 23 February 2008, B-2 “AV-12” Spirit of
Kansas crashed on the runway shortly after takeoff from Andersen Air Force Base in Guam.
Spirit of Kansas had been operated by the 393rd 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 and survived the crash. The aircraft was destroyed, a hull
loss valued at US$1.4 billion. After the accident, the Air Force took the B-2 fleet off operational
status until clearing the fleet for flight status 53 days later on 15 April 2008. 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. This was the first crash of a B-2 and the only loss as of 2019.
In February 2010, another serious incident involving a B-2 occurred at Andersen Air Force
Base. The aircraft involved was AV-11 Spirit of Washington. The aircraft was severely damaged
by fire while on the ground and underwent 18 months of repairs in order to enable it
to fly back to the mainland for more comprehensive repairs. Spirit of Washington was repaired
and returned to service in December 2013. At the time of the accident the USAF had no
training to deal with tailpipe fires on the B-2s.==Aircraft on display==No operational B-2s have been retired by the
Air Force to be put on display. B-2s have made periodic appearances on ground display
at various air shows. B-2 test article (s/n AT-1000), the second
of two built without engines or instruments for static testing, was placed on display
in 2004 at the National Museum of the United States Air Force near Dayton, Ohio. The test
article passed all structural testing requirements before the airframe failed. The museum’s restoration
team spent over a year reassembling the fractured airframe. The display airframe is marked to
resemble The Spirit of Ohio (S/N 82-1070), the B-2 used to test the design’s ability
to withstand extreme heat and cold. The exhibit features Spirit of Ohio’s nose wheel door,
with its Fire and Ice artwork, which was painted and signed by the technicians who performed
the temperature testing. The restored test aircraft is on display in the museum’s “Cold
War Gallery”.==Specifications (B-2A Block 30)==Data from USAF Fact Sheet, Pace, SpickGeneral
characteristics Crew: 2: pilot (left seat) and mission commander
(right seat) Length: 69 ft 0 in (21.0 m)
Wingspan: 172 ft 0 in (52.4 m) Height: 17 ft 0 in (5.18 m)
Wing area: 5,140 sq ft (478 m2) Empty weight: 158,000 lb (71,700 kg)
Gross weight: 336,500 lb (152,200 kg) Max takeoff weight: 376,000 lb (170,600 kg)
Fuel capacity: 167,000 pounds (75,750 kg) Powerplant: 4 × General Electric F118-GE-100
non-afterburning turbofans, 17,300 lbf (77 kN) thrust eachPerformance Maximum speed: 630 mph (1,010 km/h, 550 kn)
at 40,000 ft altitude / Mach 0.95 at sea level Cruise speed: 560 mph (900 km/h, 487 kn) at
40,000 ft altitude Range: 6,900 mi (11,000 km, 6,000 nmi) 11,100
km (6,900 mi) Service ceiling: 50,000 ft (15,200 m)
Wing loading: 67.3 lb/sq ft (329 kg/m2) Thrust/weight: 0.205Armament
2 internal bays for ordnance and payload with an official limit of 40,000 lb (18,000 kg);
maximum estimated limit is 50,000 lb (23,000 kg).80× 500 lb class bombs (Mk-82, GBU-38)
mounted on Bomb Rack Assembly (BRA) 36× 750 lb CBU class bombs on BRA
16× 2,000 lb class bombs (Mk-84, GBU-31) mounted on Rotary Launcher Assembly (RLA)
16× B61 or B83 nuclear bombs on RLA (strategic mission)
Standoff weapon: AGM-154 Joint Standoff Weapon (JSOW) and AGM-158 Joint Air-to-Surface Standoff
Missile (JASSM).==Individual aircraft==Sources: B-2 Spirit (Pace), appearances in media====
See also==Northrop YB-49
Northrop Grumman B-21 Raider Related lists List of active United States military aircraft
List of bomber aircraft List of flying wing aircraft
List of aerospace megaprojects

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