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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 able to deploy both
conventional and
thermonuclear weapons. The bomber has a crew of two and can drop up to eighty 500 lb (230 kg)-class (
Mk 82)
JDAM Global Positioning System-guided bombs, or sixteen 2,400 lb (1,100 kg)
B83 nuclear bombs. The B-2 is the only known aircraft that can carry large
air-to-surface standoff weapons in a stealth configuration.
Development originally started under the "Advanced Technology Bomber" (ATB) project during the
Carter administration, and its performance was one of his reasons for the cancellation of the supersonic
B-1A bomber. ATB continued during the
Reagan administration,
but worries about delays in its introduction led to the reinstatement
of the B-1 program as well. Program costs rose throughout development.
Designed and manufactured by
Northrop Grumman, the cost of each aircraft averaged US$737 million (in 1997 dollars).
[3] Total
procurement costs averaged $929 million per aircraft, which includes spare parts, equipment, retrofitting, and software support.
[3] The total program cost including development, engineering and testing, averaged $2.1 billion per aircraft in 1997.
[3]
Because of its considerable
capital and
operating costs, the
project was controversial in the
U.S. Congress and among the
Joint Chiefs of Staff. The winding-down of the
Cold War
in the latter portion of the 1980s dramatically reduced the need for
the aircraft, which was designed with the intention of penetrating
Soviet airspace and attacking high-value targets. During the late 1980s
and 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.
[4] A total of 20 B-2s remain in service with the
United States Air Force, which plans to operate the B-2 until 2058.
[5]
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 (11,000 km)
on internal fuel and over 10,000 nautical miles (19,000 km) with one
midair refueling. Though originally designed primarily as a nuclear bomber, it was first used in combat dropping conventional ordnance in the
Kosovo War in 1999 and saw further service in
Iraq and
Afghanistan.
[6]
Development
Origins
In the mid-1970s, the search for a new U.S.
strategic bomber aircraft to replace the
Boeing B-52 Stratofortress was underway, to no avail. First the
B-70 and then the
B-1A were canceled after only prototypes of each aircraft were built. The B-70 was intended to fly above and beyond defensive
interceptor aircraft, only to find these same attributes made it especially vulnerable to
surface-to-air missiles (SAMs). The
B-1B attempted to avoid SAMs by flying close to the ground to use
terrain to mask its
radar signature, only to face a new generation of interceptors with
look-down/shoot-down capabilities (
Mig-31 with
Zaslon PESA and
Su-27 with
Myech, guided by
A-50 airborne early warning) that could attack them from above.
[7]
Before this other projects had attempted to create a “stealth”
aircraft, but were not successful. In the 1960s, specialized drones
known as
Lightning Bugs, or
Fireflies, had been created with extra stealth features. The SR-71 used stealth to operate its missions.
[8]
By the mid-1970s, it was becoming clear that there was a different way 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 stealth characteristics would be able to fly
nearly undetected and could be attacked only by weapons and systems not
relying on radar. Although such possibilities existed, such as human
observation, their relatively short detection range allowed most
aircraft to fly undetected by defenses, especially at night.
[9]
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.
[10] 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.
[11]
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.
[12]
ATB program
By 1976, these programs progressed to where a long-range strategic
stealth bomber appeared viable. President Carter was aware of these
developments during 1977, and it appears to have been one of the major
reasons the B-1 was canceled.
[13]
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 in 1979,
Ronald Reagan repeatedly stated that Carter was weak on defense, and used the B-1 as a prime example. In return, on 22 August 1980, the
Carter administration publicly disclosed that the
United States Department of Defense (DoD) was working to develop stealth aircraft, including a bomber.
[14]
The B-2's first public display in 1988
The Advanced Technology Bomber (ATB) began in 1979.
[15] Full development of the
black project followed, and was funded under the code name "
Aurora".
[16] 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.
[15] Both teams used flying wing designs.
[16] The Northrop proposal was code named "Senior Ice" and the Lockheed proposal code named "
Senior Peg".
[17] Northrop had prior experience developing the
YB-35 and
YB-49 flying wing aircraft.
[18] The Northrop design was larger while the Lockheed design included a small tail.
[16] In 1979, designer
Hal Markarian produced a sketch of the aircraft, that bore considerable similarities to the final design.
[19] The Air Force originally planned to procure 165 of the ATB bomber.
[1]
The Northrop team's ATB design was selected over the Lockheed/Rockwell design on 20 October 1981.
[15][20]
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.
[14] An estimated US$23 billion was secretly spent for
research and development on the B-2 by 1989.
[21] MIT engineers and scientists helped assess the mission effectiveness of the aircraft under a five-year
classified contract during the 1980s.
[22]
Secrecy and espionage
The B-2's first public flight in 1989
During its design and development, the Northrop B-2 program was a Gray Project before its reveal to the public.
[23] 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, there has been considerable importance placed to the security
of the B-2 and its 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.
[24]
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 mid-1980s.
[25] Northrop (now Northrop Grumman) was the B-2's prime contractor; major subcontractors included
Boeing,
Hughes Aircraft (now
Raytheon),
GE, and
Vought Aircraft.
[6]
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.
[26] 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,
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 photographs of the aircraft's then-secret
planform
and suppressed engine exhausts from the air, to the USAF's
disappointment. The B-2's (s/n 82-1066 / AV-1) first public flight was
on 17 July 1989 from Palmdale to Edwards AFB.
[27]
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.
[28] On 9 August 2010, Gowadia was convicted in the
United States District Court for the District of Hawaii on 14 of 17 charges against him.
[29] On 24 January 2011, Gowadia was sentenced to 32 years in prison.
[30]
Program costs and procurement
A procurement of 132 aircraft was planned in the mid-1980s, but was later reduced to 75.
[31]
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.
[32]
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.
[33]
In 1995, Northrop made a proposal to the USAF to build 20 additional aircraft with a
flyaway cost of $566 million each.
[34]
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 (52.4 m)
wingspan, which are needed to maintain the aircraft's stealthy
properties, particularly its "low-observable" stealthy skins.
[35][36] Maintenance costs are about $3.4 million a month for each aircraft.
[37]
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.
[3]
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.
[3]
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.
[3] 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.
[38][39]
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, others in the Senate, such as
Jim Exon (D-NE) and
John McCain (R-AZ), also opposing the project.
[40]
The escalating cost of the B-2 program and evidence of flaws in the aircraft's ability to elude detection by radar,
[40]
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."
[41] In 1990, the Department of Defense accused Northrop of using faulty components in the
flight control system; the threat posed by bird ingestion potentially damaging engine fan blades also required redesigning.
[42]
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.
[43] 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,
[44] and that the military had greater priorities in spending a limited budget.
[45]
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 an additional 20 B-2s would cost.
[46]
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.
[47] Nonetheless, Congress did not approve funding for the purchase of any additional B-2 bombers.
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
fibre optic network; a new version of the operational flight program software was also developed, with legacy code converted from the
JOVIAL programming language used beforehand to standard
C.
[48][49] Updates were also made to the weapon control systems to enable strikes upon non-static targets, such as moving ground vehicles.
[50]
B-2 from below
On 29 December 2008, Air Force officials awarded a US$468 million
contract to Northrop Grumman to modernize the B-2 fleet's radars.
[51] Changing the radar's frequency was required as the
U.S. Department of Commerce has sold that radio spectrum to another operator.
[52] In July 2009, it was reported that the B-2 had successfully passed a major USAF audit.
[53] 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.
[54]
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.
[55] 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.
[56]
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.
[57]
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.
[58]
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.
[59]
In 2012, Air Force Chief of Staff General Norton Schwartz stated the
B-2's 1980s-era stealth would make it less survivable in future
contested airspaces, so the USAF is to proceed with the
Next-Generation Bomber despite overall budget cuts.
[60] The Next-Generation Bomber was estimated, in 2012, to have a projected overall cost of $55 billion.
[61]
In 2014 the USAF outlined a series of upgrades including nuclear war
fighting, a new integrated processing unit, the ability to carry cruise
missiles, and threat warning improvements.
[62]
Design
Side view of a B-2 Spirit
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
their ordnance, which could include
nuclear weapons.
[63] The B-2 is a
flying wing aircraft, meaning it has no fuselage or tail.
[63]
The blending of low-observable technologies with high aerodynamic
efficiency and large payload gives the B-2 significant advantages over
previous bombers. Low observability provides a greater freedom of action
at high altitudes, thus increasing both range 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).
[6][64] At cruising altitude the B-2
refuels every six hours, taking on up to 50 short tons (45 t) of fuel at a time.
[65]
Due to the aircraft's complex flight characteristics and design
requirements to maintain very-low visibility to multiple means of
detection, both the development and construction of the B-2 required
pioneering use of
computer-aided design and
manufacturing technologies.
[63][66] 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,
[67] allegedly for political reasons.
[68] The resemblance goes as far as B-2 and YB-49 having the same wingspan.
[69][70]
As of September 2013
[update] about 80 pilots fly the B-2.
[65] Each aircraft has a crew of two, a pilot in the left seat and mission commander in the right,
[6] and has provisions for a third crew member if needed.
[71] For comparison, the B-1B has a crew of four and the B-52 has a crew of five.
[6] The B-2 is highly automated and, unlike most two-seat aircraft, one crew member can sleep in a
camp bed, use a toilet, or prepare a hot meal while the other monitors the aircraft; extensive
sleep cycle and
fatigue research was conducted to improve crew performance on long
sorties.
[72][73][65]
Armaments and equipment
A 2,000 lb BDU-56 bomb is being loaded onto a bomb bay's rotary launcher, 2004
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.
[74]
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.
[75][76] The B-2 is capable of carrying 40,000 pounds of ordnance.
[6][77] 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.
[76][78]
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.
[74][79] 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;
[80] an upgrade program in 2004 raised the maximum carriable capacity to 80 JDAMs.
[81]
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.
[82]
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,
[83] the B-2 is the only platform compatible with the MOP as of 2012.
[58] As of 2011, the
AGM-158 JASSM cruise missile is an upcoming standoff munition to be deployed on the B-2 and other platforms.
[84] 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.
[85]
Avionics and systems
In order to make the B-2 more effective than any previous bomber, it
has integrated many advanced and modern avionics systems into its
design, these have been modified and improved in light of the switch to
conventional warfare missions. The B-2 features 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)
[86] and a Defensive Management System (DMS) to inform the flight crew against possible threats.
[81] The onboard DMS is capable of automatically assessing the detection capabilities of identified threats and indicated targets.
[87]
For safety and fault-detection purposes, an on-board test system is
interlinked 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.
[88] In 2008, many of the 136
[89]
standalone distributed computers on board the B-2, including the
primary flight management computer, were being replaced by a single
integrated system.
[90] 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.
[91]
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 operator's equipment.
[81] The arrays of the upgraded radar features were entirely replaced to make the AN/APQ-181 into an
active electronically scanned array (AESA) radar.
[92]
Flight controls
Vice President
Dick Cheney sits inside a B-2's cockpit with pilot Capt. Luke Jayne during a visit to Whiteman AFB in 2006.
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.
[93]
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 negatively affect the aircraft's stealth capabilities.
[94]
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.
[95]
Northrop had investigated several means of applying directional
control that would least infringe on the aircraft's radar profile,
eventually settling on a combination of split brake-rudders and
differential thrust.
[87]
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.
[96]
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.
[97]
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.
[97]
Stealth
The B-2's engines are buried within its wing to conceal the engines' fans and minimize their exhaust signature
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-2s 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
[update], there has been no instances of a missile being launched at a B-2.
[65]
To reduce optical visibility during daylight operations, the B-2 is painted in an
anti-reflective paint.
[76]
The undersides are dark because it flies at high altitudes (50,000
feet), and at that altitude a dark grey painting blends very well into
the sky. It is even possible that it has an upward-facing
light sensor which alerts the pilot to increase or reduce altitude to match the changing illuminance of the sky.
[98] 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.
[99] The bomber remains vulnerable to visual interception at ranges of 20 nm, 37 km or less by fighters.
[65]
Radar
Reportedly, the B-2 has a
radar cross-section of about 0.1 m
2.
[100](for comparison, a surface-to-air missile has roughly the same RCS, while a human has an RCS of about 1 m
2, see
Radar cross-section)
The bomber does not always fly stealthily; when nearing air defenses
pilots "stealth up" the B-2, the details of which are secret. The
aircraft disappears from radar, 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.
[63][101]
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).
[102]
Illustration of the B-2's basic radar reflection angles
RCS reduction as a result of shape had already been observed on the
Avro Vulcan bomber,
[103]
which has (apart from the vertical stabilizer) a shape most closely
resembling that of a flying wing. Northrop already had experience with
flying wing bombers when it tested the
Northrop YB-35 and
Northrop YB-49
strategic bomber prototypes in the late 1940s. Northrop engineers also
studied the RCS effects of flying wings on World War II German aircraft
(see
Horten Ho 229#Stealth technology).
The
F-117 Nighthawk uses flat surfaces (
faceting technique) for controlling radar returns because at the time when its concept (
Lockheed Have Blue)
was designed in the early 1970s; technology did not allow simulating
radar reflection for anything but very simple, flat surfaces. With
advances in computing power in the 1980s it became possible to simulate
on supercomputers the radar returns on more complex curved surfaces.
[104]
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.
[105][106]
The leading edges of the wing converge at the nose of the aircraft,
which prevents radar reflections in the direction of flight; the
W-shaped rear of the aircraft is for similar reasons.
[citation needed]
The engine air intakes are placed on the superior side of the fuselage
to minimize reflection to ground-based radar. To avoid detection by
high-flying
look-down radars, engines are buried within the B-2's wing (
S-duct) to conceal the engines' fans.
[citation needed]
The B-2 also carries all ordinance internally; the aircraft's RCS
becomes substantially larger while the bay doors are opens, making it
temporarily easier to detect.
[citation needed] The B-2 employs an AN/APQ-181
Low probability of intercept radar, designed to be difficult to detect by
passive radar
detection equipment. This characteristic is desirable in a radar as it
allows it to be used with minimal risk of revealing its presence.
[citation needed]
Infrared
The gap below the air intake has the purpose of sucking in cool air
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.
[107][108]
Burying engines deep inside the fuselage also minimizes
thermal visibility of the exhaust.
[76][109] 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 infrared spectrum) being released and thus reduces the 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.
[91] The aircraft lacks
afterburners, because the hot exhaust would increase the infrared footprint, and breaking the
sound barrier would produce an obvious
sonic boom, as well as
aerodynamic heating of the
aircraft skin which also increased 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 and lighter than aluminum. Perhaps most
crucially, a beneficial characteristic of this composite material is the
absorption of significant amounts of radar energy.
[67]
The B-2 is assembled with unusually tight
engineering tolerances to avoid leaks as they could increase its radar signature.
[72] Innovations such as alternate
high frequency
material (AHFM) and automated material application methods were also
incorporated into the aircraft to enhance its radar-absorbent properties
and lower maintenance requirements.
[76][110] In early 2004, Northrop Grumman began applying a newly developed AHFM to operational B-2s.
[111]
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.
[112]
Operational history
A B-2 during
aerial refueling which extends its range past 6,000 nautical miles (6,900 mi; 11,000 km) for intercontinental sorties
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.
[113] The B-2 reached initial operational capability (IOC) on 1 January 1997.
[114] 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.
[6]
Originally designed to deliver nuclear weapons, modern usage has
shifted towards a flexible role with conventional and nuclear
capability.
[76]
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.
[6] During this war, B-2s flew non-stop to Kosovo from their home base in Missouri and back.
[6] The B-2 was the first aircraft to deploy GPS satellite-guided
JDAM "smart bombs" in combat use in Kosovo.
[115]
The use of JDAMs and precision-guided munitions effectively replaced
the controversial tactic of carpet-bombing, which had been harshly
criticised due to it causing indiscriminate civilian casualties in prior
conflicts, such as the
1991 Gulf War.
[116] On 7 May 1999, a B-2 dropped five JDAMs on a target building that was actually the
Chinese Embassy, killing several staff.
[117]
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.
[6] B-2s would be stationed in the Middle East as a part of a US military buildup in the region from 2003.
[118]
The B-2's combat use preceded a U.S. Air Force declaration of "full operational capability" in December 2003.
[6]
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".
[6][119]
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.
[6] As of September 2013
[update] the longest combat mission has been 44.3 hours.
[65] "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,
[6] including 583 JDAM "smart bombs" in 2003.
[81]
In response to organizational issues and high-profile mistakes made within the Air Force,
[120][121] 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.
[122][123]
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.
[124]
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.
[125][126]
In August 2011,
The New Yorker reported that prior to the May 2011 U.S. special forces 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.
[127]
There were also concerns an airstrike would make it difficult to
positively identify Bin Laden's remains and so concluding he was in fact
dead would be problematic.
[128]
On 28 March 2013, two B-2s flew a round trip of 13,000 miles
(20,800 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 and 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.
[129][130]
Operators
In a 1994
live fire exercise near
Point Mugu, California, a B-2 drops 47 individual 500 lb (230 kg)-class
Mark 82 bombs, which is more than half of a B-2's total ordnance payload.
United States Air Force (20 aircraft in active inventory)
- Global Strike Command
-
- 13th Bomb Squadron 2005–
- 325th Bomb Squadron 1998–2005
- 393d Bomb Squadron 1993–
- 394th Combat Training Squadron 1996–
- Air Combat Command
-
- 72d Test and Evaluation Squadron (Whiteman) 1998–
-
- 325th Weapons Squadron 2005– (Whiteman)
- 715th Weapons Squadron 2003–05
- Air National Guard
-
- 110th Bomb Squadron
- Air Force Materiel Command
-
- 419th Flight Test Squadron 1997–
- 420th Flight Test Squadron 1992–97
- Air Force Systems Command
- 6510th Test Wing – Edwards AFB 1989–92
-
- 6520th Flight Test Squadron
Accidents
Wreckage of the 2008 B-2 crash
On 23 February 2008, B-2
Spirit of Kansas crashed on the runway shortly after takeoff from
Andersen Air Force Base in
Guam.
[131] 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. It was the first crash of a B-2. The
two person crew ejected safely from the aircraft and survived the
crash. The aircraft was completely destroyed, a
hull loss valued at US$1.4 billion.
[132][133]
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.
[134]
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.
[135]
In February 2010, another serious incident involving a B-2 occurred at Andersen AFB. 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.
[136][137] Spirit of Washington was repaired and returned to service in December 2013.
[138][139] At the time of the accident the USAF had no training to deal with tailpipe fires on the B-2s.
[140]
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.
[141] The test article passed all structural testing requirements before the airframe failed.
[142]
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.
[141] 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.
[141] The restored test aircraft is on display in the museum's "Cold War Gallery".
[143]
From 1989 to 2004, the
South Dakota Air and Space Museum located on the grounds of
Ellsworth Air Force Base displayed the 10-short-ton (9-
metric-ton) "Honda- Stealth", a 60% scale
mock-up of a stealthy bomber which had been built by North American
Honda in 1988 for an
advertising campaign.
[144]
Honda donated the model to the museum in 1989, on condition that the
model be destroyed if it was ever replaced with a different example. The
museum received a B-1 Lancer for display (Ellsworth being a B-1 base)
in 2005 and destroyed the mock-up.
[145][146]
Specifications (B-2A Block 30)
General characteristics
- Crew: 2: pilot and commander (co-pilot)
- Length: 69 ft (21.0 m)
- Wingspan: 172 ft (52.4 m)
- Height: 17 ft (5.18 m)
- Wing area: 5,140 ft² (478 m²)
- Empty weight: 158,000 lb (71,700 kg)
- Loaded weight: 336,500 lb (152,200 kg)
- Max. takeoff weight: 376,000 lb (170,600 kg)
- Powerplant: 4 × General Electric F118-GE-100 non-afterburning turbofans, 17,300 lbf (77 kN) each
- Fuel Capacity: 167,000 pounds (75,750 kg)
Performance
- Maximum speed: Mach 0.95 (550 knots, 630 mph, 1,010 km/h) at 40,000 ft altitude / Mach 0.95 at sea level[147]
- Cruise speed: Mach 0.85[64] (487 knots, 560 mph, 900 km/h) at 40,000 ft altitude
- Range: 6,000 nmi (11,100 km (6,900 mi))
- Service ceiling: 50,000 ft (15,200 m)
- Wing loading: 67.3 lb/ft² (329 kg/m²)
- Thrust/weight: 0.205
Armament
- 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).[64]
- 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)
Individual aircraft
Spirit of New York
