B-2 Spirit
The B-2 Spirit is a multi-role heavy bomber capable of delivering both conventional and nuclear munitions. The aircraft is a giant leap forward in technology and the bomber represents a milestone in the United States bomber modernization program.
The first B-2 was publicly displayed on 22 November 1988 when it was rolled out of its hangar at Air Force Plant 42, Palmdale, CA. Its first flight was on 17 July 1989.
Just like the B-52 and B-1B., the B-2 has the penetrating flexibility and effectiveness essential to manned bombers.
Its stealth characteristics give the B-2 the ability to penetrate an enemy's most sophisticated defenses and threaten its most valued and heavily defended targets, like the F-117 did in Bagdad, during the first and second war in Iraq.
History
Formal work on the development of "low-observable" or "stealth' aircraft in the US began in late 1974, when DARPA, a Pentagon organization that works on "blue sky" advanced technologies, began "Project Harvey" as an effort to build a stealthy aircraft.
Before Project Harvey, there were other attempts to incorporated stealth features into aircraft. In the early 1960s, Firebee target drones had been modified for the reconnaissance role as "Lightning Bugs" or "Fireflies". They had been fitted with stealth features, including pads of RAM on the sides of the fuselage. The drones also had a wire mesh over the air intake to mask the blades of the engine compressor, this technique was later used on the F-117 stealth fighter.
The high-flying Lockheed SR-71 Blackbird reconnaissance aircraft was designed to be stealthy as well, though it also used high altitude and speed for protection.
The goals of Project Harvey were much more ambitious: to create an aircraft that could survive on stealth alone. DARPA awarded study contracts to McDonnell Douglas and Northrop in January 1975. Lockheed found out about Harvey through the grapevine and insisted on participating, paying for their design effort out of company funds. That was a gamble, but it paid off: Northrop and Lockheed were selected by DARPA to design a stealth demonstrator, the "Experimental Survivable Testbed (XST)", while McDonnell Douglas was eliminated from the competition. The XST program's goals did not include building a flight demonstrator; Northrop and Lockheed were to build large-scale mockups, which would then be mounted on a pole at Holloman AFB in New Mexico and subjected to tests to determine their RCS.
Iin December 1976 DARPA officials called up Northrop to discuss a stealth aircraft as part of the Pentagon's "Assault Breaker" effort. DARPA wanted Northrop to study a stealthy "Battlefield Surveillance Aircraft -- Experimental (BSAX)" that would spot targets for Assault Breaker weapons. In April 1978, DARPA awarded Northrop a contract for a single flying prototype of the design, which was given the codename "Tacit Blue".
Tacit Blue performed its initial flight in February 1982, followed by 134 more flights over a three-year evaluation. Tacit Blue was put in storage in 1985 and was finally announced to the public in 1996.
While Northrop was beginning work on Tactic Blue, back at the Pentagon the top brass was becoming very interested in stealth. A group studying the military potential of stealth concluded that improvements in adversary air defenses were threatening to make the current "non-stealthy" US bomber force obsolete. In addition, stealth would allow a single aircraft to make a precision attack on a target, instead of requiring a full "strike package" of multiple bombers, with fighter escorts, jamming platforms, and defense-suppression ("Wild Weasel") aircraft.
The group recommended that two stealthy strike aircraft should be built, an "A Airplane", a fast-track development of the Lockheed Have Blue demonstrator, which would emerge as the F-117; and a "B Airplane" that would be bigger and more capable but would take more time to deliver.
The B Airplane concept grew over time into a full-blown, long-range heavy bomber. Lockheed had proposals, one apparently being a machine something like a scaled-up F-117 and codenamed "Senior Peg", but the Pentagon also asked Northrop to investigate. Northrop came up with two proposals, one of which, cooked up by designer Hal Markarian, took its inspiration from the YB-49, a flying wing design build by Northop three decades earlier. Incidentally, there is a story, possibly true, that the YB-49 had shown a surprising ability to disappear from radar at certain viewing angles.
The Northrop concept, codenamed "Senior Ice", was judged superior to the Lockheed proposal, codenamed "Senior Peg", and Northrop won the ATB contract in October 1981. The contract covered delivery of two static-test airframes, one flying prototype, and five evaluation machines. While the Carter Administration had pushed stealth there had been some ambivalence about production, but the new, hawkish Reagan Administration wanted to go full speed ahead on the ATB. The initial plan envisioned production of 127 ATBs, in addition to the five evaluation machines, which would be brought up to operational specification.The first "B-2" prototype, "Air Vehicle One (AV-1)", was rolled out at the Northrop plant in Palmdale, California, on 22 November 1988. The rollout was public, but observers were restricted to stands that kept them well away from the aircraft and limited their view of it to the front. AV-1 performed its first flight on 17 July 1989, flying from Palmdale to Edwards AFB in California. Northrop Test pilot Bruce Hinds and USAF Colonel Richard Couch were at the controls. AV-2, the first of the five evaluation machines, performed its initial flight on 19 October 1990. The first production B-2A was accepted by the US Air Force Air Combat Command (USAF ACC) at Whiteman AFB in Missouri on 17 December 1993. Due to the merger of Northrop and Grumman in the 1990s, the aircraft is now the "Northrop Grumman B-2".
The B-2 Spirit
The B-2 is organic in appearance, a simple flying wing, with absolutely no vertical control surfaces. It has very smooth contours and few features that could "catch" radar waves and reflect them. It has a sweepback of 55 degrees and a "W"-shaped trailing edge. The aircraft is aerodynamically unstable, kept in the air with a quadruple-redundant fly-by-wire (FBW) system, under the control of a General Electric Flight Control Computer (FCC).
The B-2 was designed to be survivable, not merely in penetrating enemy airspace and performing attacks, but in riding out enemy nuclear attacks or counterstrikes. The B-2 is thoroughly radiation hardened; Waaland commented that about all that isn't radiation hardened is the antiskid braking system. It can also operate from dispersed bases, one of the design criteria being the capability to use any airstrip capable of supporting a Boeing 727 airliner.
The B-2 makes heavy use of titanium for structural elements, with much of the rest of the aircraft built of carbon-reinforced plastic (CRP) material. Large CRP skin assemblies were used to make the aircraft as "seamless" as possible, reducing radar reflections. The B-2 is painted in a bluish-gray anti-reflective paint to reduce its visual signature. It is not painted black, as is the F-117, since the B-2 is expected to perform both daylight and night attacks, and black is a high-visibility color for daylight flight operations.
Engine
The B-2's four General Electric F118-GE-110 non-afterburning turbofans, providing 77 kN (8,620 kg / 19,000 lbs) of thrust each, are derived from the popular GE F110 engine. The F118s are buried in the wings, with two engines clustered together inboard on each wing. The engine intakes and exhausts are on the top of the wings for concealment. The intakes have a zigzag lip to scatter radar reflections, and there is a zigzag slot just before each intake to act as a "boundary layer splitter", breaking up the stagnant turbulent airflow that tends to collect on the surface of an aircraft. The inlet ducts are built as an s-curve and lined with RAM to keep radar from picking up the compressor blades.
As with the F-117, the B-2's engines have an exhaust temperature control system, to minimise the aircraft's thermal signature. The B-2 can fly more than 6,000 nautical miles before refueling, and more than 10,000 nautical miles with just one refueling, while carrying 40,000 pounds of weapons.
Weapons
The bomber is fitted with two side-by-side weapons bays that can accommodate a total of 22,680 kilograms (50,000 pounds) of stores. The leading and trailing edges of the weapons bay doors have the classic stealthy zigag pattern. When the doors are open, twin grilles pop out into the airstream at the front of the weapons bay to ensure proper stores separation. Each of the two weapons bays can be fitted with a Boeing Advanced Rotary Launcher (ARL), each capable of carrying eight 1,000 kilogram (2,200 pound) class munitions, or a Bomb Rack Assembly (BRA) for carriage of smaller munitions.
On March 29th, 2006, Northrop Grumman completed an upgrade of the B-2 bomber fleet that allows the it to deliver five times its previous capacity of independently targeted, "smart" (GPS-guided) weapons.
The smart bomb rack assembly (SBRA) enables the B-2 to deliver 80 500-pound smart weapons, each targeted against a different aimpoint. Northrop Grumman was responsible for development, validation and production of the SBRA system and integration of the GBU-38 (JDAM-82) 500-pound smart weapon on the B-2.
Since the B-2 was originally designed for the strategic bombing role, it was qualified initially for nuclear stores such as the B83 strategic nuclear bomb, with selectable yield in the megatonne range, and the smaller B61 "Silver Bullet" nuclear bomb, with selectable yield in the range of hundreds of kilotonnes. The bomber was later qualified for the penetrating B61-11 penetrating nuclear weapon. A B-2 can carry 16 nuclear stores.
Radar
The service is currently modifying the B-2A's existing APQ-181 multimode navigation and attack radar, built by Raytheon, to prevent a potential spectrum conflict starting as soon as 2007 with worldwide users of commercial satellites that transmit high definition TV and digital motion picture signals. Flight testing expected to begin in April 2006.
The changes include incorporating two active electronically scanned array (AESA) radar antennas onto the aircraft, one for each side, along with some improved computer processors. The upgraded radar will still operate in the Ku-band, but use a different frequency to prevent damaging the commercial satellites.
Installation of the new antenna on the B-2 fleet is to be completed by 2010.
B-2 in Service
Although the Air Force had accepted their first B-2 in late 1993, the B-2 remained in service test for several more years, not reaching formal initial operational capability until 1997. The USAF only obtained a total of 20 operational aircraft. The small production buy meant that the high development costs were spread over a handful of aircraft, and since the program costs were about $48 billion USD, that came to about $2.4 billion USD per aircraft. Had more B-2s been built, of course their incremental cost would have been much less, though still clearly in the hundreds of millions of dollars.
The first ten B-2s delivered to the Air Force, from December 1993 to late 1995, were "Block 10" machines, intended for service evaluation and training. They couldn't fly at full flight loads, lacked precision weapons guidance and terrain following capability, and had a limited DMS. Eight "Block 20" machines were delivered in 1996 and 1997, which were up to operational specification, along with some improvements such as a Global Positioning System (GPS) satellite navigation receiver. The GPS receiver system was integrated into a "GPS Aided Targeting System (GATS)" to support the GAM GPS-guided bomb, and later the JDAM and other GPS-guided weapons. The ten Block 10s were brought up to Block 20 specification.
The Block 20s were followed by two final new-build "Block 30" aircraft, with the older machines brought up to the same specification. The Block 30s have avionics improvements, including a satellite communications (SATCOM) link; the lidar contrail-detection system; support for new GPS-guided weapons; and in particular have substantial modifications to improve their stealthiness. Adding the new stealth features require stripping off all the aircraft's paint and RAM and performing some airframe changes.
The B-2 went into combat for the first time on the night of 24 March 1999, at the very start of Operation Allied Force, the NATO air campaign against Serbia. The B-2 dropped JDAM GPS-guided bombs in the opening phases of the campaign to cripple Serbian air defenses so that conventional strike aircraft could operate with greater safety. The B-2 continued to fly strikes against well-defended targets during the rest of the campaign, unfortunately acquiring a bit of notoriety on 7 May 1999 when a B-2 dropped JDAM's on the Chinese embassy in Belgrade. The Chinese government protested loudly and angrily. The blunder was due to bad intelligence and mission planning, not a technical failure or crew error.
Six B-2s were committed to Operation Enduring Freedom, the American intervention in Afghanistan in 2001/2002, performing strikes in the early phases of the conflict. One mission lasted 44 hours, the longest combat sortie in the history of air warfare, with B-2s flying out of Whiteman to Afghanistan, dropping their loads, and then landing on Diego Garcia island in the Indian ocean to refuel, rearm, and take on new crews while the engines remained on idle. This done, the B-2s went back to Afghanistan to drop their loads, and finally returned to Whiteman. Four B-2s were also committed to Operation Iraqi Freedom, the American invasion of Iraq in the spring of 2003.
Recent developments (news)
Northrop Grumman Delivers First Operational B-2 Bomber With New Radar
Posted at: Tue Apr 28th, 2009 | Source: Northrop Grumman
WHITEMAN AFB, Mo., April 28, 2009 (GLOBE NEWSWIRE) -- Northrop Grumman Corporation (NYSE:NOC) has delivered to the U.S. Air Force the first operational B-2 Spirit stealth bomber to be equipped with a newly modernized radar. The aircraft was officially handed...
F-22s, B-2s conduct historic overseas deployment to the Pacific
Posted at: Wed Apr 22nd, 2009 | Source: US Air Force
ANDERSEN AIR FORCE BASE, Guam -- Twelve F-22 Raptors departed here recently following a historic deployment marking the first time, F-22 Raptors and B-2 Spirits, the key national strategic stealth assets in the Air Fo...
B-2 aircrew participates in exercise in Pacific
Posted at: Fri Mar 20th, 2009 | Source: AFNS
ANDERSEN AIR FORCE BASE, Guam (AFNS) -- Airmen aboard a B-2 Spirit tested their endurance in a 24-hour, 8,000-mile mission to Alaska and back to Guam March 12 in an exercise showcasing U.S. commitment to peace and stability throughout the Pacific region.&nb...
| 
