The Northrop (later Northrop Grumman) B-2 Spirit, also known as the Stealth Bomber, is an American low-observable, strategic, long-range, heavy bomber capable of penetrating sophisticated and dense air-defence shields.The bomber can deploy both conventional and thermonuclear weapons, such as eighty 500 lb (230 kg)-class (Mk 82) JDAM Global Positioning System-guided bombs, or sixteen 2,400 lb (1,100 kg) B83 nuclear bombs.It is capable of all-altitude attack missions up to 50,000ft, with a range of more than 6,000nm unrefuelled and over 10,000nm with one refuelling, giving it the ability to fly to any point in the world within hours.
Its distinctive profile comes from the unique 'flying wing' construction. The leading edges of the wings are angled at 33° and the trailing edge has a double-W shape.
It is manufactured at the Northrop Grumman facilities in Pico Rivera and Palmdale in California.
Development originally started under the "Advanced Technology Bomber" (ATB) project during the Carter administration, and its expected 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, 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 including development, engineering and testing, averaged $2.1 billion per aircraft in 1997.
Six prototypes were funded and the first was rolled out on 22 November 1988. The B-2's first flight took place on 17 July 1991 the USAF implemented a set of treatments to rectify a shortfall in the B-2A's stealth capabilities.
The USAF had originally wanted 132 aircraft, but funding restrictions have seen the fleet completed with just 21 aircraft. In 2008 one aircraft crashed leaving a current number of 20. The last of these was delivered on 14 July 2000 and is the AV-1 prototype upgraded to Block 30 standard. The first operational B-2A was delivered to the 509th Bomb Wing on 17 December 1993 and full initial operating capability came in April 1997.
Having progressed through the Block 10 and 20 standards of stealth, systems and weapons capability, the entire B-2A fleet will be brought to Block 30 standard with full weapons and stealth capabilities. The B-2A made its combat debut over Kosovo in 1999, employing the Joint Direct Attack Munition (JDAM) and other weapons to great effect. Although the USAF's B-2 force is garrisoned at Whiteman Air Force base, Missouri, the service has ambitious plans to operate the aircraft temporarily from forward bases like Guam and Diego Garcia.
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 their ordnance, which could include nuclear weapons. The B-2 is a flying wing aircraft, meaning it has no fuselage or tail. The blending of low-observable technologies with high aerodynamic efficiency and large payload gives the B-2 significant advantages over previous bombers. Low observability provides a greater freedom of action at high altitudes, thus increasing both range and field of view for onboard sensors. The U.S. Air Force reports its range as approximately 6,000 nautical miles (6,900 mi; 11,000 km). At cruising altitude the B-2 refuels every six hours, taking on up to 50 short tons (45 t) of fuel at a time.
The contoured wing of the B-2 Spirit contains the crew compartment, payload bays, and engines. This engine placement thereby buries the highly radar reflective fan and turbine blades within the bomber's interior. In addition to radar absorbant materials (RAM) covering its surface, the external lines of the B-2 are alligned in a parallel arrangement to scatter radar waves away from their point of origin. Also, the engine exhaust is vented through a long trough covered with heat-absorbing materials to reduce the B-2's infrared heat signature.
AHFM stealth coating
Northrop Grumman has developed a new radar-absorbent coating to preserve the B-2's stealth characteristics while drastically reducing maintenance time. The new material, known as alternate high-frequency material (AHFM), is sprayed on by four independently controlled robots.
In November 2011, the USAF awarded a $109m contract to Northrop Grumman for producing a redesigned aft deck for the B-2 stealth bomber.
B-2 Cockpit
The cockpit accommodates two crew. It is equipped with a colour, nine-tube, electronic flight instrumentation system (EFIS), which displays flight, engine and sensor data and avionics systems and weapons status.
The pilot can choose to activate the appropriate selection of flight and mission equipment for take-off mode, go-to-war mode and landing mode by using a simple three-way switch.
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 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. 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.
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| Light surface below wing edges is the AN/APQ-181 radar antenna |
The Raytheon AN/APQ-181 covert strike radar, operating at J band (Ku band), is a multi-purpose radar with terrain following and terrain avoidance modes. Testing at Edwards Air Force Base has demonstrated reliable terrain following at altitudes down to 200ft.
In April, 2009 Northrop Grumman Corporation delivered to the US Air Force the first operational B-2 Spirit stealth bomber to be equipped with newly modernised radar. The aircraft was officially handed off to the air force on at Whiteman Air Force Base, the operational home of the B-2 fleet and the 509th Bomb Wing.
The updated aircraft will be used by air force to conduct additional field testing of the radar, and the data gathered from these decisions will support future fielding decisions.
The B-2 radar modernisation programme replaces the aircraft's original radar system with one that incorporates technology improvements that have occurred since the B-2 was originally designed in the early 1980s.
In November 2002, Raytheon was awarded a contract to develop a new Ku-band AESA (active electronically scanned array) antenna for the B-2 radar to avoid interference with commercial satellite systems after 2007. Flight tests with new radar began in October 2007 and continued until 2008. Installation of the new antenna on the B-2 fleet is to be completed by 2012.
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 feet), 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 (37 km) or less.
Navigation and communications
The B-2's navigation suite includes a Rockwell Collins TCN-250 tactical air navigation system (TACAN) and a VIR-130A instrument landing system.
The communications equipment is supplied by Rockwell Collins. A Milstar military strategic and tactical relay satellite communications system is installed in block 30 aircraft.
The aircraft have been upgraded with Link 16 communications link.
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| Agm-129 acm |
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| A B83 casing. |
The aircraft carries all its weapons internally and is fitted with two separate weapons bays in the centre of the aircraft. The B-2 has the capacity to carry up to 40,000lb of weapons, including conventional and nuclear weapons, precision-guided munitions, gravity bombs and a range of maritime weapons.
Each weapons bay is equipped with a rotary launcher and two bomb-rack assemblies. In tests, the B-2 successfully released B-61 and B-83 nuclear and mk84 conventional bombs from the rotary rocket launcher, and mk82 and CBU-87 conventional weapons from the bomb racks. The B61-11 is an earth-penetrating nuclear bomb for use against deeply buried and hardened targets. The B83 is a strategic free-fall nuclear bomb.
The B-2 can also carry the AGM-129 advanced cruise missile, which is a strategic cruise missile with a range estimated at up to 1,500 miles.
16 satellite-guided JDAM (joint direct attack munition) missiles can be carried. Northrop Grumman is converting the B-2 bomb rack assembly to a new 'smart' configuration, which will increase the number of JDAMs which can be carried to a maximum of 80. The aircraft will also be fitted with the joint stand-off weapon (JSOW), joint air-to-surface stand-off missiles (JASSM) and the wind-compensated munitions dispenser (WCMD) and will be able to carry up to 80 115kg small diameter bombs (SDB).
In June 2007, Northrop Grumman was awarded a contract to integrate the Boeing massive ordnance penetrator (MOP) weapon on the B-2. The MOP is GPS-guided, contains 2,400kg (5,300lb) of explosive and is designed to penetrate hardened, deeply buried targets. B-2 is capable of carrying two MOP weapons, one in each weapons bay.
A generic weapons interface system (GWIS) has been fitted as part of the block 30 upgrade. The GWIS is an integrated digital software package, which allows the B-2 to carry different mixes of stand-off weapons and direct attack munitions on a single sortie, enabling the aircraft to attack up to four different types of targets on a single mission.
Under a contract awarded to Northrop Grumman in February 2008, the USAF has begun a programme to give the B-2 the capability to attack moving targets, using precision-guided weapons such as the small diameter bomb II.
Countermeasures
The B-2 carries a Lockheed Martin radar warning receiver, a Northrop Grumman defensive aids system and the Lockheed Martin AN/APR-50 defensive management system (DMS).
Engine
The aircraft is powered by four General Electric F118-GE-100 turbofan engines internally mounted in the body of the wings.
The engines have an exhaust temperature control system to minimise thermal signature.
The engines, rated at 77kN, provide a high subsonic speed and a maximum gross take-off weight of 336,500lb. In-flight refuelling gear is installed in the top centre line of the aircraft behind the cockpit.
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 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.
B-2 deliveries and bases
21 B-2s have been delivered to Whiteman Air Force Base in Missouri, the first in December 1993.
A new transportable hangar system has been developed which allows the B-2 to be deployed to forward locations overseas.
The hangars are 126ft long, 250ft wide and 55ft high. The first of these hangars has been erected on Diego Garcia in the Indian Ocean.
Prior to this development, B-2s had to return to Whiteman AFB after missions, for maintenance of the aircraft's stealth features. The B-2 was thus deployed for the first time during Operation Iraqi Freedom in March / April 2003. In March 2005, a B-2 squadron was deployed for the first time to Andersen Air Force Base in Guam in support of the USAF Pacific Command.
On 23 February 2008, a B-2 crashed shortly after take-off from Andersen AFB in Guam, the first crash in the aircraft's history. The two pilots ejected safely from the aircraft, which was not carrying munitions. A USAF investigation into the causes of the crash is underway. The B-2 fleet was grounded pending the results of the investigation but was returned to service in April 2008. A USAF investigation released an accident report in June 2008 which concluded that the crash was caused by moisture in the port transducer units. These sensors sent distorted information to the air data system.
Specifications (B-2A Block 30)
Data from USAF Fact Sheet, Pace, Spick
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
Cruise speed: Mach 0.85[63] (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).
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).