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The Northrop Grumman B-2 Spirit Stealth Bomber

v1.0.6 / 01 jan 14 / greg goebel / public domain

* During the late 1940s and early 1950s, Jack Northrop of the Northrop company worked on a series of flying-wing bombers, none of which actually reached production. However, they did attract a great deal of public attention, being seen as futuristic, and were even featured in science-fiction movies such as THE WAR OF THE WORLDS.

A few decades later the notion that the future belonged to the flying wing seemed laughable, but Northrop had the last laugh. There were tales that radar had trouble picking up the uncluttered lines of a flying wing, and as the US Air Force turned towards "stealthy" aircraft in the 1970s and 1980s, the flying wing bomber was revived in the form of the Northrop Grumman "B-2 Spirit", the first flying wing to enter full operational service, the biggest stealth aircraft built to date, and one of the most expensive aircraft ever made.

Northrop Grumman B-2 Spirit


[1] B-2 ORIGINS: PROJECT HARVEY / TACIT BLUE / ATB
[2] B-2 DESCRIBED
[3] B-2 IN SERVICE
[4] COMMENTS, SOURCES, & REVISION HISTORY

[1] B-2 ORIGINS: PROJECT HARVEY / TACIT BLUE / ATB

* Formal work on the development of "low-observable" or "stealth' aircraft in the US began in late 1974, when the Defense Advanced Research Projects Agency (DARPA), a Pentagon organization that works on "blue sky" advanced technologies, began Project HARVEY, an effort to build a stealthy aircraft. The project was named after a famous comedy about a giant invisible rabbit named, of course, Harvey.

Project HARVEY was not actually the first time the US had 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 enhanced with stealth features, including pads of radar-absorbing material (RAM) on the sides of the fuselage; and a wire mesh over the air intake to mask the blades of the engine compressor, which tends to sparkle or "glint" on radar as it spins, like a spinning disco ball in a lights show. 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 officials 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 "radar cross section (RCS)".

Work on the Northrop demonstrator was conducted by a team under John Cashen, a pushy sort who had come to Northrop after working at Hughes on how targets appeared to radar and infrared sensors, and Irv Waaland, a designer who had come over to Northrop from Grumman. Although the Lockheed team used a computer program to come up with their design for the XST, Cashen said later that Northrop didn't have such a luxury, and worked up their design using a combination of theoretical analysis and cut-and-try experiments.

The Lockheed team won the XST competition in March 1976, and went on to build two HAVE BLUE stealth demonstrator aircraft, which paved the way to the larger Lockheed F-117 stealth fighter. Northrop lost because one the team's initial design assumptions was that a stealthy aircraft should be hardest to pick up from the front and below, but the DARPA requirement, rightly or wrongly, insisted on measuring stealthiness from four quadrants. The Lockheed design proved better able to meet the all-round stealth requirement. Lockheed also had an advantage in possessing a good knowledge of RAM technology, which that company had developed for the SR-71.

However, in December 1976 DARPA officials called up Northrop to discuss a stealth aircraft as part of the Pentagon's ASSAULT BREAKER effort. ASSAULT BREAKER was a wide-ranging program that envisioned use of new "smart" munitions, deep-penetrating strike platforms, and advanced sensors to smash numerically-superior Soviet armor forces in the case of a European war. DARPA wanted Northrop to study a stealthy "Battlefield Surveillance Aircraft -- Experimental (BSAX)" that would spot targets for ASSAULT BREAKER weapons. Since BSAX was supposed to loiter around a battlefield instead of performing an attack and leaving, it would present all angles to an enemy and so required all-round stealth. An initial model of BSAX was tested in the summer of 1977, with results that Waaland later described as "disastrous". One of the design team members, Fred Oshira, did some rethinking of the design and came up with a solution, a new airframe design that gave very little for a radar beam to grab on to. 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 with Boeing Bird of Prey

TACIT BLUE performed its initial flight in February 1982, followed by 134 more flights over a three-year evaluation. It was unarguably one of the ugliest aircraft ever built, unflatteringly known as the "Whale". It featured a fuselage resembling a stretched upside-down bathtub with a wedge-shaped flat panel under the nose; an engine intake buried in the back; wedge-shaped wings; and a vee tail shielding the exhaust. TACIT BLUE was powered by twin high-bypass turbofan engines, had a wingspan of 14.7 meters (48 feet 2 inches), a length of 17 meters (55 feet 10 inches), and a weight of 13,605 kilograms (30,000 pounds).

In 1984, the Army and Air Force decided to collaborate on a non-stealthy battlefield surveillance platform, which would emerge as the E-8 Joint Stars, based on the Boeing 707 airliner. TACIT BLUE was put in storage in 1985. It was finally announced to the public in 1996, and is now on display in the USAF Museum at Wright Patterson Air Force Base in Ohio.

* While Northrop was beginning work on TACTIC BLUE, back at the Pentagon the top brass were becoming very interested in stealth. In 1977, William "Bill" Perry, Secretary of Defense for the Carter Administration, formed a group to perform studies on the military potential of stealth. The group's conclusion was 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 roll out.

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 officials were uneasy about working on a heavy bomber, since the company's last effort along such lines, the XB-35 / YB-49 flying wings of three decades earlier, had come close to financially wrecking the company. They did agree, however, and responded with two proposals, one of which, cooked up by designer Hal Markarian, took its inspiration from the YB-49. 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 proposals were duly submitted in August 1979, and Bill Perry came back with a study contract, asking Northrop to refine the flying wing concept. Waaland joined up with Markarian, and the team also acquired aerodynamicist Hans Grellman, as well as Dick Scherrer, a designer who had recently come over from Lockheed. At the outset, the Northrop "Advanced Strategic Penetration Aircraft (ASPA)", as it was known, was seen strictly as an insurance policy, since Lockheed was regarded by the brass as the front-runner.

However, by the time the Air Force issued a request for an "Advanced Technology Bomber" in September 1980, formalizing the ASPA studies into a program to develop an operational aircraft, Northrop's design was looking much more attractive, and company officials felt they had a shot at winning the contract. Lockheed was partnering with Raytheon on their ATB proposal, and so Northrop approached Boeing to sign up as a partner. Northrop's chairman, Tom Jones, had a meeting with his counterpart at Boeing, Thornton Wilson. Wilson, to his embarrassment, was almost completely ignorant of the ATB program, but Jones filled him in, and Wilson agreed to join immediately. Witnesses claim that Wilson then turned to one of his people and said: "Don't ever let me be caught in this position again!"

The Northrop concept, codenamed SENIOR ICE, was judged superior to the Lockheed SENIOR PEG proposal, 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 Pentagon wanted to keep the contract a secret, but Tom Jones pointed out that Northrop had to publicly declare large company contracts in order to be in compliance with securities laws. Government officials, caught by their own regulations, issued the shortest and least informative statement possible about the contract. It would be the last public mention of the program until 1988.

* There was much more work to be done to get such a complicated machine into the air, all the more so because the ATB requirements had expanded over time. Aircraft size and munitions load had grown, and although the ATB was originally seen as a high-altitude penetration machine, the Air Force decided that a low altitude capability would be nice as well -- there was no saying that the Soviets might eventually develop more powerful and smarter radars that could pick up a high-flying stealthy aircraft.

In any case, the work went forward, and 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. Although the F-117 had been kept secret for years after its first flight, its test flights had been restricted to night, and that wasn't regarded as acceptable for the B-2. Since it would have been quickly spotted during daylight flights, there was no sense it keeping it a complete secret, and nobody tried.

However, the security restrictions at the rollout weren't completely "airtight", in a highly literal sense of the word. The late Michael A. Dornheim, a reporter from AVIATION WEEK magazine, flew a light aircraft over the B-2 and had a photographer take pictures, obtaining one of the magazine's biggest scoops of all time and justifying its nickname of AVIATION LEAK. It was all perfectly legal. The damage, if any, had been done, and the program went forward. 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".

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[2] B-2 DESCRIBED

* 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 are used to make the aircraft as "seamless" as possible, reducing radar reflections. The principle of seamlessness also means that the number of access panels has been minimized, reversing the trend of the past decades to provide maximum maintenance access. Maintenance access is mostly provided through absolutely essential apertures, such as the bombbays and crew boarding hatch. There are also no drain holes, with drainage flowing into collectors that are emptied on the ground.

Designing the CRP assemblies, tooling up for their production, and fitting them in place in aircraft manufacture was a major engineering challenge. Special heat-resistant CRP formulations are used around engine exhausts and other hot spots, where carbon-reinforced epoxy simply won't do. The aircraft was initially coated with a conductive elastomer material to ensure that it had uniform electrical conductivity. This material was not actually RAM, but RAM was used selectively where needed. 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.

The leading edge of the wing has an internal structure that helps it absorb radar energy. The outermost wing segment features a "rudderon" or "deceleron", a vertically-split airbrake / rudder that simultaneously opens up and down. To act as an airbrake, both the decelerons are opened, while to act as a rudder only one is. This clever gimmick goes back to the original Northrop flying wings. There is an elevon inboard of the deceleron on the outermost segment of each wing, and then two elevons further inboard, on the next segment. Finally, there is a single control surface for pitch control on the "beavertail" at the center end of the aircraft, giving a total of nine control surfaces.

The decelerons have to be opened about five degrees before they are effective, and in normal cruising flight they are left slightly open. However, this undermines stealth, so when the bomber is in hostile airspace, it uses differential engine thrust for yaw control.

B-2 with F-117 stealth fighters

* The B-2's four General Electric F118-GE-100 non-afterburning bypass turbojets, providing 84.56 kN (8,620 kgp / 19,000 lbf) 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. An AlliedSignal auxiliary power unit is fitted on the forward end of the left engine assembly for engine starting and ground power. The B-2 also features a built-in halon engine fire extinguishing system.

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.

The exhaust is mixed with airflow obtained through the boundary layer splitter slot to reduce the infrared signature. The aircraft was also designed to eliminate its contrail, with a tank outboard of the main landing gear to store a chemical that would be mixed with the exhaust flow to suppressed the formation of a contrail. This scheme wasn't actually used in practice, with a "lidar" (laser radar) system instead eventually developed to detect the formation of a contrail and alert the pilot to descend to lower altitude.

   NORTHROP GRUMMAN B-2A:
   _____________________   _________________   ______________________
 
   spec                    metric              english
   _____________________   _________________   ______________________

   wingspan                52.43 meters        172 feet
   wing area               490.05 sq_meters    5,275 sq_feet
   length                  21.03 meters        69 feet
   height                  5.18 meters         17 feet

   empty weight            45,400 kilograms    100,000 pounds
   max loaded weight       181,400 kilograms   400,000 pounds

   maximum speed           764 KPH             475 MPH / 416 KT
   service ceiling         +15,240 meters      +50,000 feet
   range                   11,675 kilometers   7,255 MI / 6,310 NMI
   _____________________   _________________   ______________________

The B-2 has tricycle landing gear, with twin-wheel nose gear and four-wheel bogey systems for the main gear. The main gear is built by Boeing and is derived from that used on the Boeing 767 airliner. The landing gear doors have stealthy zigzag leading and trailing edges. Since it is difficult to find a place on the smoothly-contoured airframe to paint such "display" items as the aircraft name or serial number, they are painted on the main gear outer doors, making them visible to onlookers when the aircraft is on the ground, or during takeoff and landing. There is a boom-refueling port in the center of the back, which is normally covered by doors and pops up when needed.

* 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 zigzag pattern. When the doors are open, twin grilles pop out into the airstream at the front of each weapons bay to ensure proper stores separation. Each of the two weapons bays can be fitted with a Boeing Advanced Rotary Launcher (ARL), capable of carrying eight 1,000 kilogram (2,200 pound) class munitions, or a Bomb Rack Assembly (BRA) for carriage of smaller munitions.

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.

The B-2 has also been qualified for use with "dumb" bombs, such as sixteen 900 kilogram (2,000 pound) bombs, or eighty 225 kilogram (500 pound) bombs or cluster munitions based on the Tactical Munitions Dispenser (TMD). However, such stores are likely better carried by other platforms such as the B-52 or B-1B, and so the emphasis with the B-2 has been on precision-guided weapons. Some sources claim it can also carry the AGM-84 Harpoon antiship missile for maritime strike, but it seems more likely that this was simply listed as a potential store as a political expedient to emphasize additional roles for the B-2. It is unclear if a B-2 has ever fired a Harpoon.

A Global Positioning System (GPS) guided bomb, the "GPS Aided Munition (GAM)", was developed on a fast-track basis for the B-2, but GAM was strictly an interim fix until the real solution, the "Joint Direct Attack Munition (JDAM)", was introduced in the late 1990s. JDAM was initially a 900 kilogram bomb fitted with gliding strakes and GPS guidance; kits were later introduced for 225 kilogram bombs as well. The B-2 can also carry the AGM-154 Joint Stand-Off Weapon (JSOW) glide bomb, and the AGM-158 Joint Air to Surface Standoff Missile (JASSM).

* The B-2 is highly automated and only requires two crew. A centerbody provides crew accommodation, with crew access through a hatch in the belly. The cockpit has large windows, so large in fact that they tend to make the B-2 look smaller than it really is, though the downward view is poor. Fighter pilots taking the controls of the B-2 say it makes them feel like they are "flying in a dumpster". A fine wire mesh is built into the windows to block radar signals.

The two crew sit side-by-side on ACES II zero-zero (zero speed, zero altitude) ejection seats, which blast through frangible roof panels. The "mission commander", who handles navigation and weapons delivery, sits on the left, while the pilot sits on the right. The mission commander is also a rated pilot and can fly the aircraft if need be. They control the aircraft using a "glass cockpit", with each crew using a dashboard featuring four 15 centimeter (6 inch) color CRT multifunction displays (MFDs) and a fighter-style control stick. There was provision for a third seat in case the crew workload proved too high, but a third crewperson proved unnecessary. A chemical toilet and rollup mattress can be carried for long missions. It is unclear if there are other conveniences, such as a small refrigerator or microwave oven.

The B-2's original "Navigation Sub-System (NSS)" included a Kearfott Inertial Management Unit and a Northrop NAS-26 "Astro-Inertial Unit (AIU)", which obtains position fixes using a telescope to lock on to star positions, using a noticeable port on top of the wing off to the left side of the cockpit. It even works in daylight when the bomber is at high altitude, and is a descendant of an AIU developed for the SR-71.

The B-2 is fitted with an AN/APQ-181 radar, with some similarities to the AN/APG-70 used on the F-15E Strike Eagle fighter. The AN/APQ-181 is a Ku band (high microwave, from 12 GHz / 3 centimeters to 18 GHz / 2 centimeters) radar, with an electronically steered antenna in the lower leading edge of each wing. The Ku band suffers from greater atmospheric attenuation than lower frequency bands, but it also provides very high resolution for navigation and targeting.

The AN/APQ-181 provides "low probability of intercept (LPI)" operation, with the radar dancing over frequencies and changing pulse patterns so that its signals can't be picked out of background noise until it's too late. Apparently the TACIT BLUE program did much to advance LPI radar technology; it would have made absolutely no sense to design a stealthy battlefield surveillance aircraft and then have it announce its presence by blasting out strong and easily detected radar signals. The AN/APQ-181 provides 20 operational modes, including:

Finally, the B-2 includes a countermeasures suite, the "Defensive Management System (DMS)", the details of which generally remain secret. All the avionics systems are controlled by a total of 13 radiation-hardened "Avionics Control Units (ACUs)", run by sophisticated software to help reduce flight load and provide cockpit data display to enhance the crew's "situational awareness".

* B-2 aircrew find the big bomber a very pleasant ride and easy to fly. Its FBW system offloads a good deal of the work, and a flying wing is about as aerodynamically clean an aircraft design as could be conceived. It is an aircraft that wants to get into the air but doesn't want to come back down, and so pilots have to use steep carrier-style landings. Apparently this causes some problems when they go back to more conventional aircraft and end up making excessively hard landings.

B-2 down and dirty on approach

The aerodynamic cleanliness of the B-2 makes it very responsive to throttle changes. Midair refueling also takes a little practice, since once the B-2 gets into the slipstream of the tanker the bomber tends to slide forward a bit. The B-2 is very stable, and by the other side of the same coin not particularly maneuverable. B-52 aircrew moving up to the B-2 find it more agile than the "Buff", but B-1B aircrew feel the "Bone" is superior in this respect, and with its higher wing loading the B-1B also gives a smoother low-level ride than the B-2. The B-2s systems are complicated and require extensive training to master, but aircrew who grew up on computer games find the systems aspect fun and no monster to deal with.

Although the official name of the B-2 is "Spirit", as is usually the case with official names, the aircrews don't call it that; apparently there is no particular nickname. However, all the operational B-2s have been given SPIRIT OF names, such as SPIRIT OF TEXAS, SPIRIT OF KANSAS, SPIRIT OF CALIFORNIA, and so on. Only one doesn't use a US state in the name: number 82-1066 is, appropriately, SPIRIT OF HASTINGS. All fly out of Whiteman AFB with the USAF 509th Bomb Wing.

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[3] B-2 IN SERVICE

* As mentioned, the Air Force originally planned a total of 132 B-2 bombers as the airborne leg of the nuclear "triad" of bombers, land-based missiles, and submarine-launch missiles that comprise America's nuclear deterrent. In reality, the end of the Cold War meant that the need for new strategic weapons systems had greatly diminished. In addition, the B-2 was a highly advanced aircraft, leading to program glitches, cost escalations, schedule stretchouts, furious political controversies, and repeated cuts in production numbers.

Although the Air Force had accepted the 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.

Stripping off the aircraft's surface layers is tricky, since it has to be done without damaging the composite skin or resulting in massive amounts of toxic solvents that would be a pain to dispose of properly. Northrop Grumman came up with a scheme in which the aircraft is air-blasted with crystallized wheat starch, a substance that resembles granulated sugar. The starch proved able to remove coatings without damaging the composite skin. Not only is disposal of the starch relatively straightforward, it can be reused about ten times; in fact, it becomes more effective after three or four cycles.

B-2 refuels in midair

* 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 JDAMs 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.

The first B-2 to be lost was the SPIRIT OF KANSAS, which suffered a takeoff accident at Andersen AFB on Guam on 23 February 2008. The two crew were able to eject safely. The particular aircraft had been built in 1989 and had almost 5,200 flight hours on it, out of an expected total flight lifetime of 40,000 hours.

* An improved coating scheme, which provides an overall coating of RAM, was developed after the introduction of the Block 30. The new coating scheme not only reduces RCS, but reduces maintenance time per flight hour from 20.8 hours to 9.2 hours. The old scheme used caulk and tape to seal off the radar-reflective edges of access panels. This was not only labor intensive, but the tape tended to strip off in flight. The new scheme does not seal off the edges; the RAM coating absorbs RF energy that penetrates into cracks. There has been work on further improved coatings.

The updated surface coating scheme has opened new options for the B-2. The aircraft has a bay outboard of each of the main landing gear that was originally supposed to store contrail-suppression chemicals but was never used. The two bays are about 2.75 meters (9 feet) long and are as deep as the wing. USAF officials think that the bays could be used to store a pair of decoys or small cruise missiles.

Along with the improved coatings, the B-2 has also received new bomb racks that allow it to carry up to 80 GPS-guided weapons. In a particularly significant upgrade, in the summer of 2004 the Air Force awarded a contract under the "Radar Modernization Program (RMP)" for the development of a modernized radar system for the B-2, based on "active electronically scanned array (AESA)" technology. An AESA features an antenna made up of a grid of smart transmit-receive elements that can cooperate to perform functions or perform multiple functions in parallel. There were delays in the program but the first upgraded B-2 with the new radar went back into service in 2009.

The new B-2 radar resolves conflicts that existed between the bomber's radar and commercial systems, and allows the bomber to communicate and exchange target data with other platforms; maintenance is reduced as well, partly because of the elimination of moving parts. The B-2's defensive management system and radar transponder is also being updated as part of the effort. New stores have been qualified, particularly the little 125 kilogram (250 pound) winged "Small Diameter Bomb II (SDB II)", and the huge 13,100 kilogram (28,900 pound) "Massive Ordnance Penetrator (MOP)" GPS-guided bunker-buster, with the B-2 to carry two MOPs.

Other improvements being implemented or planned include:

Currently, the Air Force envisions the B-2 remaining in service until 2040 at least. The fact that the airframe is largely made of composites makes it corrosion-resistant, and it's flight profiles are generally benign, meaning it should live well longer than that. The Air Force is working on a replacement, the "Long Range Strike Bomber (LRSB)", but it's essentially an investigation at present. Concepts being floated envision a stealthy flying wing along the lines of the B-2, but cheaper and -- at least in later development, "optionally piloted", capable of performing unmanned operations when necessary.

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[4] COMMENTS, SOURCES, & REVISION HISTORY

* In 1994, the Planes of Fame air museum in Chino, California, restored to flight status the N-9M, one of Jack Northrop's single-seat experimental flying wing prototypes. In February 1995, it flew to Edwards AFB to commemorate the 50th anniversary of its first flight in 1945 by being photographed next to a B-2. B-2 test pilot Bruce Hinds used the opportunity to take the N-9M out for a spin.

I saw a B-2 in flight for the first time at an airshow in Denver in the spring of 2007. That fall I was on a road trip from Colorado to Florida and made a stop at a zoo near Salina, Kansas. While I was going into the zoo I saw a sci-fi-looking aircraft near the horizon. I got a zoom shot of it with my camera to confirm that it was a B-2. I was a bit surprised to see it there, but as I drove into Missouri I went past Whiteman AFB and made the connection.

Northrop Grumman B-2 Spirit

* Sources include:

* Revision history:

   v1.0.0 / 01 dec 03
   v1.0.1 / 01 oct 05 / Review & polish.
   v1.0.2 / 01 sep 07 / Review & polish.
   v1.0.3 / 01 apr 08 / Added crash of SPIRIT OF KANSAS.
   v1.0.4 / 01 mar 10 / Review & polish.
   v1.0.5 / 01 feb 12 / Review & polish.
   v1.0.6 / 01 jan 14 / Review & polish.
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