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169-675: The North American Aviation XB-70 Valkyrie is a retired prototype version of the planned B-70 nuclear -armed, deep-penetration supersonic strategic bomber for the United States Air Force Strategic Air Command . Designed in the late 1950s by North American Aviation (NAA) to replace the B-52 Stratofortress and B-58 Hustler , the six-engine, delta-winged Valkyrie could cruise for thousands of miles at Mach 3+ while flying at 70,000 feet (21,000 m). At these speeds, it

338-517: A canard surface and a delta wing , which was built largely of stainless steel , sandwiched honeycomb panels, and titanium . The XB-70 was designed to use supersonic technologies developed for the Mach ;3 SM-64 Navaho , as well as a modified form of the Navaho's inertial guidance system. The XB-70 used compression lift , which resulted from a shock wave generated by the leading edge of

507-568: A honeycomb-shaped foil core. Expensive titanium would be used only in high-temperature areas like the leading edge of the horizontal stabilizer, and the nose. To cool the interior, the XB-70 pumped fuel en route to the engines through heat exchangers. On 30 August 1957, the Air Force decided that enough data were available on the NAA and Boeing designs that a competition could begin. On 18 September,

676-639: A mockup , which is an inert representation of a machine's appearance, often made of some non-durable substance. An electronics designer often builds the first prototype from breadboard or stripboard or perfboard , typically using "DIP" packages. However, more and more often the first functional prototype is built on a "prototype PCB " almost identical to the production PCB, as PCB manufacturing prices fall and as many components are not available in DIP packages, but only available in SMT packages optimized for placing on

845-553: A second (thus defining the speed of light to be 299,792,458 meters per second). In many sciences, from pathology to taxonomy, prototype refers to a disease, species, etc. which sets a good example for the whole category. In biology, prototype is the ancestral or primitive form of a species or other group; an archetype. For example, the Senegal bichir is regarded as the prototypes of its genus, Polypterus . Boeing B-52 Stratofortress The Boeing B-52 Stratofortress

1014-420: A 2,000-hour service life extension to select airframes in 1966–1968, and the extensive Pacer Plank reskinning, completed in 1977. The wet wing introduced on G and H models was even more susceptible to fatigue, experiencing 60% more stress during a flight than the old wing. The wings were modified by 1964 under ECP 1050 . This was followed by a fuselage skin and longeron replacement ( ECP 1185 ) in 1966, and

1183-667: A 50/50 blend of Fischer–Tropsch process (FT) synthetic fuel and conventional JP-8 jet fuel, which burned in two of the eight engines. On 15 December 2006, a B-52 took off from Edwards with the synthetic fuel powering all eight engines, the first time a USAF aircraft was entirely powered by the blend. The seven-hour flight was considered a success. This program is part of the Department of Defense Assured Fuel Initiative , which aimed to reduce crude oil usage and obtain half of its aviation fuel from alternative sources by 2016. On 8 August 2007, Air Force Secretary Michael Wynne certified

1352-518: A B-52 to carry twenty-four GBU-38 500-pound guided bombs or twenty GBU-31 2,000-pound bombs, with later phases accommodating the JASSM and MALD family of missiles. In addition to carrying more smart bombs, moving them internally from the wings reduces drag and achieves a 15 percent reduction in fuel consumption. The US Air Force Research Lab is investigating defensive laser weapons for the B-52. The B-52

1521-425: A PCB. Builders of military machines and aviation prefer the terms "experimental" and "service test". In electronics , prototyping means building an actual circuit to a theoretical design to verify that it works, and to provide a physical platform for debugging it if it does not. The prototype is often constructed using techniques such as wire wrapping or using a breadboard , stripboard or perfboard , with

1690-441: A chemical-fuel bomber with Mach 0.9 cruising speed and "maximum possible" speed during a 1,000-nautical-mile (1,200 mi; 1,900 km) entrance and exit from the target. The requirement also called for a 50,000-pound (23,000 kg) payload and a combat radius of 4,000 nautical miles (4,600 mi; 7,400 km). The Air Force formed similar requirements for a WS-110L intercontinental reconnaissance system in 1955, but this

1859-425: A concept was technically feasible, but by March 1957, engine development and wind tunnel testing had progressed enough to suggest that it was. WS-110 was redesigned to fly at Mach 3 for the entire mission. Zip fuel was retained for the engine's afterburner to increase range. Both North American and Boeing returned new designs with very long fuselages and large delta wings. They differed primarily in engine layout;

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2028-454: A conventional jet engine, thrust is provided by heating air using jet fuel and accelerating it out a nozzle. In a nuclear engine, heat is supplied by a reactor, whose consumables last for months instead of hours. Most designs also carried a small amount of jet fuel for high-power portions of flight, such as takeoffs and high-speed dashes. Another possibility being explored at the time was the use of boron -enriched " zip fuels ", which increase

2197-478: A digital interface ( MIL-STD-1760 ) and rotary launcher. IWBU is expected to cost roughly US$ 313   million. The 1760 IWBU will allow the B-52 to carry eight JDAM 2,000-pound (910 kg) bombs, AGM-158B JASSM-ER cruise missile and the ADM-160C MALD-J decoy missiles internally. All 1760 IWBUs should be operational by October 2017. Two bombers will have the ability to carry 40 weapons in place of

2366-579: A dry thrust of 10,000 pounds-force (44 kN) which could be increased for short periods to 11,000 pounds-force (49 kN) with water injection . The water was carried in a 360 US gallons (1,400 L) tank in the rear fuselage. B-52B, C, D and E models were equipped with Pratt & Whitney J57-P-29W, J57-P-29WA, or J57-P-19W series engines all rated at 10,500 lbf (47 kN). The B-52F and G models were powered by Pratt & Whitney J57-P-43WB turbojets, each rated at 13,750 pounds-force (61.2 kN) static thrust with water injection. On 9 May 1961,

2535-529: A favorite among US Military modelers), railroad equipment, motor trucks, motorcycles, and space-ships (real-world such as Apollo/Saturn Vs, or the ISS). As of 2014, basic rapid prototype machines (such as 3D printers ) cost about $ 2,000, but larger and more precise machines can cost as much as $ 500,000. In architecture , prototyping refers to either architectural model making (as form of scale modelling ) or as part of aesthetic or material experimentation , such as

2704-414: A final attempt to increase range, Boeing created the larger 464-67, stating that once in production, the range could be further increased in subsequent modifications. Following several direct interventions by LeMay, Boeing was awarded a production contract for thirteen B-52As and seventeen detachable reconnaissance pods on 14 February 1951. The last major design change—also at General LeMay's insistence—was

2873-554: A four-volume report on the B-70 that was published by NASA in April 1972. On 7 May 1965, a 3-foot (1 m) piece of the apex of the wing broke off in flight and caused extensive damage to five of the six engines. They were sent to GE and repaired. The sixth engine was inspected and re-installed in the aircraft. On 14 October 1965, AV-1 surpassed Mach 3, but heat and stress damaged the honeycomb panels, leaving 2 ft (60 cm) of

3042-561: A full-pressure test; the resulting explosion severely damaged the trailing edge of the wing, necessitating considerable repairs. The YB-52, the second XB-52 modified with more operational equipment, first flew on 15 April 1952 with "Tex" Johnston as the pilot. A 2-hour, 21-minute proving flight from Boeing Field , near Seattle , Washington, to Larson Air Force Base was undertaken with Boeing test pilot Johnston and USAF Lieutenant Colonel Guy M. Townsend . The XB-52 followed on 2 October 1952. The thorough development, including 670 days in

3211-487: A mid-air collision with an F-104 while flying in a multi-aircraft formation. Sonic boom and later testing continued with XB-70A #1. The second flight research program (NASA NAS4-1174) investigated "control of structural dynamics" from 25 April 1967 through the XB-70's last flight in 1969. At high altitude and high speed, the XB-70A experienced unwanted changes in altitude. NASA testing from June 1968 included two small vanes on

3380-633: A neatly bound 33-page proposal and a 14-inch (36 cm) scale model. The aircraft was projected to exceed all design specifications. Although the full-size mock-up inspection in April 1949 was generally favorable, range again became a concern since the J40s and early model J57s had excessive fuel consumption. Despite talk of another revision of specifications or even a full design competition among aircraft manufacturers, General LeMay, now in charge of Strategic Air Command, insisted that performance should not be compromised due to delays in engine development. In

3549-703: A proposal for a four-engine turbojet bomber. Joined by Ed Wells, Boeing's vice president of engineering, the engineers worked that night in The Hotel Van Cleve in Dayton, Ohio, redesigning Boeing's proposal as a four-engine turbojet bomber. On Friday, Colonel Warden looked over the information and asked for a better design. Returning to the hotel, the Boeing team was joined by Bob Withington and Maynard Pennell, two top Boeing engineers who were in town on other business. By late Friday night, they had laid out what

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3718-597: A smaller aircraft while flying in close formation; the remaining Valkyrie bomber is in the National Museum of the United States Air Force near Dayton, Ohio. In an offshoot of Boeing 's MX-2145 crewed boost-glide bomber project, Boeing hired RAND Corporation in January 1954 to explore what sort of bomber aircraft would be needed to deliver the various nuclear weapons under development. At

3887-426: A speed of Mach 3.05 while flying at 72,000 ft (22,000 m). AV-2 reached a top speed of Mach 3.08 and maintained it for 20 minutes on 12 April 1966. On 19 May 1966, AV-2 reached Mach 3.06 and flew at Mach 3 for 32 minutes, covering 2,400 mi (3,900 km) in 91 minutes of total flight. A joint NASA/USAF research program was conducted from 3 November 1966 to 31 January 1967 for measuring

4056-418: A straight-wing aircraft powered by six Wright T35 turboprops with a gross weight of 360,000 pounds (160,000 kg) and a combat radius of 3,110 miles (2,700 nmi; 5,010 km), was declared the winner. On 28 June 1946, Boeing was issued a letter of contract for US$ 1.7   million to build a full-scale mockup of the new XB-52 and do preliminary engineering and testing. However, by October 1946,

4225-499: A switch from the B-47 style tandem seating to a more conventional side-by-side cockpit, which increased the effectiveness of the copilot and reduced crew fatigue. Both XB-52 prototypes featured the original tandem seating arrangement with a framed bubble-type canopy (see above images). Tex Johnston noted, "The B-52, like the B-47, utilized a flexible wing. I saw the wingtip of the B-52 static test airplane travel 32 feet (9.8 m), from

4394-496: A time of gunpowder when we spoke of bombers in the missile age". In December 1959 the Air Force announced the B-70 project would be cut to a single prototype, and most of the planned B-70 subsystems would no longer be developed. Then interest increased due to the politics of presidential campaign of 1960 . A central plank of John F. Kennedy 's campaign was that Eisenhower and the Republicans were weak on defense, and pointed to

4563-499: A time to the initial prototype. In many programming languages , a function prototype is the declaration of a subroutine or function (and should not be confused with software prototyping). This term is rather C / C++ -specific; other terms for this notion are signature , type and interface . In prototype-based programming (a form of object-oriented programming ), new objects are produced by cloning existing objects, which are called prototypes. The term may also refer to

4732-642: A top speed of 500 miles per hour (430 kn; 800 km/h) and an 8,000-mile (7,000 nmi; 13,000 km) range, far beyond the capabilities of the 464-29. The outright cancellation of the Boeing contract on 11 December 1947 was staved off by a plea from its president William McPherson Allen to the Secretary of the Air Force Stuart Symington . Allen reasoned that the design was capable of being adapted to new aviation technology and more stringent requirements. In January 1948, Boeing

4901-451: A top speed of 513 miles per hour (446 kn; 826 km/h) at 35,000 feet (11,000 m), a range of 6,909 miles (6,004 nmi; 11,119 km), and a 280,000-pound (130,000 kg) gross weight, which included 10,000 pounds (4,500 kg) of bombs and 19,875 US gallons (75,240 L) of fuel. In May 1948, Air Materiel Command asked Boeing to incorporate the previously discarded jet engine, with improvements in fuel efficiency , into

5070-472: A way that the Planck constant h is prescribed a value of exactly 6.626 070 15 × 10  joule-second (J⋅s) Until 1960, the meter was defined by a platinum-iridium prototype bar with two marks on it (that were, by definition, spaced apart by one meter), the international prototype of the metre , and in 1983 the meter was redefined to be the distance in free space covered by light in 1/299,792,458 of

5239-518: Is a form of functional or working prototype. The justification for its creation is usually a data migration , data integration or application implementation project and the raw materials used as input are an instance of all the relevant data which exists at the start of the project. The objectives of data prototyping are to produce: To achieve this, a data architect uses a graphical interface to interactively develop and execute transformation and cleansing rules using raw data. The resultant data

North American XB-70 Valkyrie - Misplaced Pages Continue

5408-541: Is an American long-range, subsonic , jet-powered strategic bomber . The B-52 was designed and built by Boeing , which has continued to provide support and upgrades. It has been operated by the United States Air Force (USAF) since the 1950s, and NASA for nearly 50 years. The bomber can carry up to 70,000 pounds (32,000 kg) of weapons and has a typical combat range of around 8,800 miles (14,200 km) without aerial refueling . Beginning with

5577-517: Is becoming practical to eliminate the creation of a physical prototype (except possibly at greatly reduced scales for promotional purposes), instead modeling all aspects of the final product as a computer model . An example of such a development can be seen in Boeing 787 Dreamliner , in which the first full sized physical realization is made on the series production line. Computer modeling is now being extensively used in automotive design, both for form (in

5746-440: Is due to receive a range of upgrades alongside a planned engine retrofit. These upgrades aim to modernize the sensors and displays of the B-52. They include the new APG-79B4 Active electronically scanned array radar, replacing older mechanically scanned arrays, the streamlining of the nose and deletion of blisters housing the forward-looking infrared/electro-optical viewing system. In October 2022 Boeing released new images of what

5915-475: Is officially listed as 50,000 feet (15,000 m), but operational experience shows this is difficult to reach when fully laden with bombs. According to one source: "The optimal altitude for a combat mission was around 43,000 feet (13,000 m), because to exceed that height would rapidly degrade the plane's range." In September 2006, the B-52 became one of the first US military aircraft to fly using alternative fuel. It took off from Edwards Air Force Base with

6084-431: Is possible that a prototype may fail to perform acceptably although the production design may have been sound. Conversely, prototypes may perform acceptably but the production design and outcome may prove unsuccessful. In general, it can be expected that individual prototype costs will be substantially greater than the final production costs due to inefficiencies in materials and processes. Prototypes are also used to revise

6253-414: Is then evaluated and the rules refined. Beyond the obvious visual checking of the data on-screen by the data architect, the usual evaluation and validation approaches are to use Data profiling software and then to insert the resultant data into a test version of the target application and trial its use. When developing software or digital tools that humans interact with, a prototype is an artifact that

6422-499: Is used as the standard of measurement of some physical quantity to base all measurement of that physical quantity against. Sometimes this standard object is called an artifact . In the International System of Units ( SI ), there remains no prototype standard since May 20, 2019 . Before that date, the last prototype used was the international prototype of the kilogram , a solid platinum-iridium cylinder kept at

6591-409: Is used to ask and answer a design question. Prototypes provide the means for examining design problems and evaluating solutions. HCI practitioners can employ several different types of prototypes: In the field of scale modeling (which includes model railroading , vehicle modeling, airplane modeling , military modeling, etc.), a prototype is the real-world basis or source for a scale model—such as

6760-630: The AGM-154 glide bomb and the AGM-158 JASSM missile. The CEM program also introduced new radios, integrated Global Positioning System into the aircraft's navigation system, and replaced the under-nose FLIR with a more modern unit. Forty-seven B-52Hs were modified under the CEM program by 1996, with 19 more by the end of 1999. By around 2010, U.S. Strategic Command stopped assigning B61 and B83 nuclear gravity bombs to B-52, and later listed only

6929-467: The B-2 as tasked with delivering strategic nuclear bombs in budget requests. Nuclear gravity bombs were removed from the B-52's capabilities because it is no longer considered survivable enough to penetrate modern air defenses, instead relying on nuclear cruise missiles and focusing on expanding its conventional strike role. The 2019 "Safety Rules for U.S. Strategic Bomber Aircraft" manual subsequently confirmed

North American XB-70 Valkyrie - Misplaced Pages Continue

7098-534: The B-52 with the Mach 2 top speed of the Convair B-58 Hustler . The new bomber was expected to enter service in 1963. Nuclear and conventional designs were considered. The nuclear-powered bomber was organized as " Weapon System 125A " and pursued simultaneously with the jet-powered version, "Weapon System 110A". The USAF Air Research and Development Command's (ARDC) requirement for WS-110A asked for

7267-519: The B-52 Stability Augmentation and Flight Control program ( ECP 1195 ) in 1967. Fuel leaks due to deteriorating Marman clamps continued to plague all variants of the B-52. To this end, all aircraft variants were subjected to Blue Band (1957), Hard Shell (1958), and finally QuickClip (1958) programs. The latter fitted safety straps that prevented catastrophic loss of fuel in case of clamp failure. The B-52's service ceiling

7436-594: The Bureau International des Poids et Mesures (International Bureau of Weights and Measures) in Sèvres France (a suburb of Paris ) that by definition was the mass of exactly one kilogram . Copies of this prototype are fashioned and issued to many nations to represent the national standard of the kilogram and are periodically compared to the Paris prototype. Now the kilogram is redefined in such

7605-732: The Chairman of the Joint Chiefs of Staff , Air Force General Nathan Twining , recommended the Air Force's plan for the B-70 to reconnoiter and strike rail-mobile Soviet ICBMs, but the Chief of Staff of the Air Force , General Thomas White , admitted the Soviets would "be able to hit the B-70 with rockets" and requested the B-70 be downgraded to "a bare minimum research and development program" at $ 200 million for fiscal year 1960 (equivalent to $ 2.1 billion today). President Eisenhower responded that

7774-711: The Davis-Monthan AFB Boneyard . The bombers flew under the Strategic Air Command (SAC) until it was disestablished in 1992 and its aircraft absorbed into the Air Combat Command (ACC); in 2010, all B-52 Stratofortresses were transferred from the ACC to the new Air Force Global Strike Command (AFGSC). The B-52 completed 60 years of continuous service with its original operator in 2015. After being upgraded between 2013 and 2015,

7943-528: The Forty Wall House open source material prototyping centre in Australia. Architects prototype to test ideas structurally, aesthetically and technically. Whether the prototype works or not is not the primary focus: architectural prototyping is the revelatory process through which the architect gains insight. In the science and practice of metrology , a prototype is a human-made object that

8112-589: The Greek πρωτότυπον prototypon , "primitive form", neutral of πρωτότυπος prototypos , "original, primitive", from πρῶτος protos , "first" and τύπος typos , "impression" (originally in the sense of a mark left by a blow, then by a stamp struck by a die (note "typewriter"); by implication a scar or mark; by analogy a shape i.e. a statue, (figuratively) style, or resemblance; a model for imitation or illustrative example—note "typical"). Prototypes explore different aspects of an intended design: In general,

8281-719: The House Armed Services Committee (HASC) on 24 January 1962 that the B-70 was unjustifiable, LeMay subsequently argued for the B-70 to both the House and Senate committees—and was chastised by McNamara on 1 March. By 7 March 1962, the HASC, 21 of whose members had B-70 work in their districts, had written an appropriations bill to "direct"—by law—the Executive Branch to use all of the nearly $ 500 million (equivalent to $ 5 billion today) appropriated for

8450-805: The McDonnell Douglas F/A-18 Hornet , the General Dynamics F-16 Fighting Falcon and the McDonnell Douglas AV-8B Harrier II . The ability to carry up to 20 AGM-69 SRAM nuclear missiles was added to G and H models, starting in 1971. To further improve its offensive ability, air-launched cruise missiles (ALCMs) were fitted. After testing of both the USAF-backed Boeing AGM-86 Air Launched Cruise Missile and

8619-536: The Prototype Javascript Framework . Additionally, the term may refer to the prototype design pattern. Continuous learning approaches within organizations or businesses may also use the concept of business or process prototypes through software models. The concept of prototypicality is used to describe how much a website deviates from the expected norm, and leads to a lowering of user preference for that site's design. A data prototype

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8788-606: The Rapid Eight program. The Conventional Enhancement Modification (CEM) program gave the B-52H a more comprehensive conventional weapons capability, adding the modified underwing weapon pylons used by conventional-armed B-52Gs, Harpoon and Have Nap, and the capability to carry new-generation weapons including the Joint Direct Attack Munition (JDAM) and Wind Corrected Munitions Dispenser guided bombs,

8957-596: The Soviet Union 's Tupolev Tu-144 SST program. The development of the Lockheed U-2 and the SR-71 Blackbird reconnaissance aircraft , as well as the XB-70, prompted Soviet aerospace engineers to design and develop their high-altitude and high-speed MiG-25 interceptor . The Valkyrie was designed to be a high-altitude Mach 3 bomber with six engines. Harrison Storms shaped the aircraft with

9126-552: The Space Shuttle , was the B-52's main computer. In 2007, the LITENING targeting pod was fitted, which increased the effectiveness of the aircraft in the attack of ground targets with a variety of standoff weapons, using laser guidance , a high-resolution forward-looking infrared sensor ( FLIR ), and a CCD camera used to obtain target imagery. LITENING pods have been fitted to a wide variety of other US aircraft, such as

9295-489: The elevator is also very narrow chord and the B-52 suffers from limited elevator control authority. For long-term pitch trim and airspeed changes the aircraft uses a stabilator (or all-moving tail) with the elevator used for small adjustments within a stabilizer setting. The stabilizer is adjustable through 13 degrees of movement (nine up, four down) and is crucial to operations during takeoff and landing due to large pitch changes induced by flap application. B-52s prior to

9464-421: The energy density of jet fuel by about 40 percent, and could be used in modified versions of existing jet engine designs. Zip fuels appeared to offer sufficient performance improvement to produce a strategic bomber with supersonic speed. The Air Force followed these developments closely, and in 1955 issued General Operational Requirement No. 38 for a new bomber, combining the payload and intercontinental range of

9633-421: The styling and aerodynamics of the vehicle) and in function—especially for improving vehicle crashworthiness and in weight reduction to improve mileage. The most common use of the word prototype is a functional, although experimental, version of a non-military machine (e.g., automobiles, domestic appliances, consumer electronics) whose designers would like to have built by mass production means, as opposed to

9802-577: The wind tunnel and 130 days of aerodynamic and aeroelastic testing, paid off with smooth flight testing. Encouraged, the USAF increased its order to 282 B-52s. Only three of the 13 B-52As ordered were built. All were returned to Boeing and used in their test program. On 9 June 1952, the February 1951 contract was updated to order the aircraft under new specifications. The final 10, the first aircraft to enter active service, were completed as B-52Bs. At

9971-404: The "fuel pressurization and inerting system " vaporized a 700-pound (320 kg) supply of liquid nitrogen to fill the fuel tank vent space and maintain tank pressure. The XB-70's maiden flight was on 21 September 1964. In the first flight test, between Palmdale and Edwards AFB, one engine had to be shut down shortly after take-off, and an undercarriage malfunction warning meant that the flight

10140-413: The 36 that three B-52s can carry. The 1760 IWBU allows precision-guided missiles or bombs to be deployed from inside the weapons bay; the previous aircraft carried these munitions externally on the wing hardpoints . This increases the number of guided weapons ( Joint Direct Attack Munition or JDAM) a B-52 can carry and reduces the need for guided bombs to be carried on the wings. The first phase will allow

10309-577: The AN/ASQ-151 Electro-Optical Viewing System (EVS), which consisted of a low light level television (LLLTV) and a forward looking infrared (FLIR) system mounted in blisters under the noses of B-52Gs and Hs between 1972 and 1976. The navigational capabilities of the B-52 were later augmented with the addition of GPS in the 1980s. The IBM AP-101 , also used on the Rockwell B-1 Lancer bomber and

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10478-573: The AN/ASQ-38 bombing navigational computer and the terrain computer. The MADREC (Malfunction Detection and Recording) upgrade fitted to most aircraft by 1965 could detect failures in avionics and weapons computer systems and was essential in monitoring the AGM-28 Hound Dog missiles. The electronic countermeasures capability of the B-52 was expanded with Rivet Rambler (1971) and Rivet Ace (1973). To improve operations at low altitudes,

10647-406: The Air Force issued operational requirements that called for a cruising speed of Mach 3.0 to 3.2, an over-target altitude of 70,000–75,000 ft (21,000–23,000 m), a range of up to 10,500 miles (16,900 km), and a gross weight not to exceed 490,000 pounds (220,000 kg). The aircraft would have to use the hangars, runways and handling procedures used by the B-52. On 23 December 1957,

10816-623: The B-47 came to an end, the Wichita factory was phased in for B-52D production, with Seattle responsible for 101 D-models and Wichita 69. Both plants continued to build the B-52E, with 42 built at Seattle and 58 at Wichita, and the B-52F (44 from Seattle and 45 from Wichita). For the B-52G, Boeing decided in 1957 to transfer all production to Wichita, which freed up Seattle for other tasks, in particular,

10985-646: The B-52 Stratofortress replaced the Convair B-36 Peacemaker . Superior performance at high subsonic speeds and relatively low operating costs have kept them in service despite the development of more advanced strategic bombers, such as the Mach 2+ Convair B-58 Hustler , the canceled Mach 3 North American XB-70 Valkyrie , the variable-geometry Rockwell B-1 Lancer , and the stealth Northrop Grumman B-2 Spirit . A veteran of several wars,

11154-476: The B-52 has dropped only conventional munitions in combat. The B-52's official name Stratofortress is rarely used; informally, the aircraft has become commonly referred to as the BUFF ( Big Ugly Fat Fucker / Fella ). There are 76 aircraft in inventory as of 2024 ; 58 operated by active forces ( 2nd Bomb Wing and 5th Bomb Wing ), 18 by reserve forces ( 307th Bomb Wing ), and about 12 in long-term storage at

11323-450: The B-52's 70,000 pounds (32,000 kg), the bombers are rarely able to carry their full loads. The most the B-52 carries is a full load of AGM-86Bs totaling 62,660 pounds (28,420 kg). The B-1 has the internal weapons bay space to carry more GBU-31 JDAMs and JASSMs, but the B-52 upgraded with the conventional rotary launcher can carry more of other JDAM variants. The AGM-183A Air-Launched Rapid Response (ARRW) hypersonic missile and

11492-465: The B-52H as fully approved to use the FT blend. Because of the B-52's mission parameters, only modest maneuvers would be required with no need for spin recovery. The aircraft has a relatively small, narrow chord rudder , giving it limited yaw control authority. Originally an all-moving vertical stabilizer was to be used but was abandoned because of doubts about hydraulic actuator reliability. Because

11661-595: The B-52H began to be delivered to the USAF with cleaner burning and quieter Pratt & Whitney TF33-P-3 turbofans with a maximum thrust of 17,100 pounds-force (76 kN). In a study for the USAF in the mid-1970s, Boeing investigated replacing the engines, changing to a new wing, and other improvements to upgrade B-52G/H aircraft as an alternative to the B-1A, then in development. In 1996, Rolls-Royce and Boeing jointly proposed fitting each B-52 with four leased Rolls-Royce RB211 engines. This would have involved replacing

11830-452: The B-58, suffered even more in relative terms. At high altitudes, the B-70 was as much as four times as fast as the B-52, but at low altitudes it was limited to only Mach 0.95, only modestly faster than the B-52 at the same altitudes. It also had a smaller bomb load and shorter range. Its only major advantage would be its ability to use high speed in areas without missile cover, especially on

11999-627: The B-70 as an example. He told a San Diego audience near NAA facilities, "I endorse wholeheartedly the B-70 manned aircraft." Kennedy also made similar campaign claims regarding other aircraft: near the Seattle Boeing plant he affirmed the need for B-52s and in Fort Worth he praised the B-58. The Air Force changed the program to full weapon development and awarded a contract for an XB-70 prototype and 11 YB-70s in August 1960. In November 1960,

12168-470: The B-70 program received a $ 265 million (equivalent to $ 2.7 billion today) appropriation from Congress for FY 1961. Nixon, trailing in his home state of California, also publicly endorsed the B-70, and on 30 October Eisenhower helped the Republican campaign with a pledge of an additional $ 155 million ($ 1.6 billion today) for the B-70 development program. On taking office in January 1961, Kennedy

12337-597: The B-70 was to replace the B-52 in the long-range role, SAC had introduced the B-58 Hustler to replace the Boeing B-47 Stratojet in the medium-range role. The Hustler was expensive to develop and purchase, and required enormous amounts of fuel and maintenance in comparison to the B-47. It was estimated that it cost three times as much to operate as the much larger and longer-ranged B-52. The B-70, designed for even higher speeds, altitudes and range than

12506-587: The B-70 would add little performance for the high cost. After becoming the new Air Force Chief of Staff in July 1961, Curtis LeMay increased his B-70 advocacy, including interviews for August Reader's Digest and November Aviation Week articles, and allowing a 25 February General Electric tour at which the press was provided artist conceptions of, and other info about, the B-70. Congress had also continued B-70 appropriations to resurrect bomber development. After Secretary of Defense Robert McNamara explained again to

12675-649: The F-108 would share two of the engines, the escape capsule, and some smaller systems with the B-70. In early 1960, North American and the USAF released the first drawing of the XB-70 to the public. The B-70 was planned to use a high-speed, high-altitude bombing approach that followed a trend of bombers flying progressively faster and higher since the start of crewed bomber use. Through that same period, only two weapons proved effective against bombers: fighter aircraft and anti-aircraft artillery (AAA). Flying higher and faster made it more difficult for both; higher speeds allowed

12844-454: The G models had very small ailerons with a short span that was approximately equal to their chord. These "feeler ailerons" were used to provide feedback forces to the pilot's control yoke and to fine-tune the roll axes during delicate maneuvers such as aerial refueling. Due to twisting of the thin main wing, conventional outboard flap-type ailerons would lose authority and therefore could not be used. In other words, aileron activation would cause

13013-568: The NAA design arranged its six engines in a semi-circular duct under the rear fuselage, while the Boeing design used separate podded engines located individually on pylons below the wing, like the Hustler. North American scoured available literature to find any additional advantage. This led them to an obscure report by two NACA wind tunnel experts, who wrote a report in 1956 titled "Aircraft Configurations Developing High Lift-Drag Ratios at High Supersonic Speeds". Known today as compression lift ,

13182-708: The Navy-backed General Dynamics AGM-109 Tomahawk , the AGM-86B was selected for operation by the B-52 (and ultimately by the B-1 Lancer). A total of 194 B-52Gs and Hs were modified to carry AGM-86s, carrying 12 missiles on underwing pylons, with 82 B-52Hs further modified to carry another eight missiles on a rotary launcher fitted in the bomb bay. To conform with SALT II Treaty requirements that cruise missile-capable aircraft be readily identifiable by reconnaissance satellites,

13351-612: The North American proposal was declared the winner of the competition, and on 24 January 1958, a contract was issued for Phase 1 development. In February 1958, the proposed bomber was designated B-70 , with the prototypes receiving the "X" experimental prototype designation . The name " Valkyrie " was the winning submission in early 1958, selected from 20,000 entries in a USAF "Name the B-70" contest. The Air Force approved an 18-month program acceleration in March 1958 that rescheduled

13520-488: The RS-70 (see Variants ). McNamara was unsuccessful with an address to the HASC on 14 March, but a 19 March 1962 11th hour White House Rose Garden agreement between Kennedy and HASC chairman Carl Vinson retracted the bill's language and the bomber remained canceled. The XB-70s were intended to be used for the advanced study of aerodynamics , propulsion , and other subjects related to large supersonic transports. The crew

13689-651: The USAAF began to express concern about the sheer size of the new aircraft and its inability to meet the specified design requirements. In response, Boeing produced the Model 464, a smaller four-engine version with a 230,000-pound (100,000 kg) gross weight, which was briefly deemed acceptable. Subsequently, in November 1946, the Deputy Chief of Air Staff for Research and Development, General Curtis LeMay , expressed

13858-606: The USAF released its request for proposals for 608 commercial engines plus spares and support equipment, with the plan to award the contract in May 2021. This Commercial Engine Reengining Program (CERP) saw General Electric propose its CF34-10 and Passport turbofans, Pratt & Whitney its PW800 , and the Rolls-Royce BR725 to be designated F130 . On 24 September 2021, the USAF selected the Rolls-Royce F130 as

14027-547: The advent of intercontinental ballistic missiles (ICBMs) during the late 1950s, crewed nuclear bombers were increasingly seen as obsolete. The USAF eventually gave up fighting for its production and the B-70 program was cancelled in 1961. Development was then turned over to a research program to study the effects of long-duration high-speed flight. As a result, two prototype aircraft, designated XB-70A, were built; these aircraft were used for supersonic test-flights from 1964 to 1969. In 1966, one prototype crashed after colliding with

14196-418: The aircraft could weigh up to 480,000 pounds (220,000 kg). Boeing responded with two models powered by T35 turboprops. The Model 464-16 was a "nuclear only" bomber with a 10,000-pound (4,500 kg) payload, while the Model 464-17 was a general purpose bomber with a 9,000-pound (4,100 kg) payload. Due to the cost associated with purchasing two specialized aircraft, the USAAF selected Model 464–17 with

14365-410: The aircraft has eight engines, asymmetrical thrust due to the loss of an engine in flight would be minimal and correctable with the narrow rudder. To assist with crosswind takeoffs and landings the main landing gear can be pivoted 20 degrees to either side from neutral. The crew would preset the yaw adjustable crosswind landing gear according to wind observations made on the ground. Like the rudder,

14534-414: The aircraft to "crab" or roll with a sideways slip angle down the runway). After a trip to a hobby shop for supplies, Schairer set to work building a model. The rest of the team focused on weight and performance data. Wells, who was also a skilled artist, completed the aircraft drawings. On Sunday, a stenographer was hired to type a clean copy of the proposal. On Monday, Schairer presented Colonel Warden with

14703-445: The aircraft to maintain directional stability at high speeds. NAA's solution had an additional advantage, as it decreased the surface area of the rear of the wing when the panels were moved into their high-speed position. This helped offset the natural rearward shift of the center of pressure , or "average lift point", with increasing speeds. Under normal conditions this caused an increasing nose-down trim, which had to be offset by moving

14872-701: The amount of visible sky, but doing so would limit its radar range in the same way as the missile sites, as well as greatly increasing fuel use and thus reducing mission time. The Soviet Union would not introduce an interceptor with look-down capability until 1972 with the High Lark radar in the MiG-23M , and even this model had very limited capability. Strategic Air Command found itself in an uncomfortable position; bombers had been tuned for efficiency at high speeds and altitudes, performance that had been purchased at great cost in both engineering and financial terms. Before

15041-431: The arrival of the B-52. The aircraft will be able to receive information through Link-16 . CONECT upgrades will cost US$ 1.1   billion overall and take several years. Funding has been secured for 30 B-52s; the USAF hopes for 10 CONECT upgrades per year, but the rate has yet to be decided. Weapons upgrades include the 1760 Internal Weapons Bay Upgrade (IWBU), which gives a 66 percent increase in weapons payload using

15210-483: The bomber to fly out of range of the weapons more quickly, while higher altitudes increased the time needed for fighters to climb to the bombers, and greatly increased the size of the AAA weapons needed to reach those altitudes. As early as 1942, German flak commanders had already concluded that AAA would be essentially useless against jet aircraft, and began development of guided missiles to fill this role. Most forces reached

15379-475: The cabin included the crew ejection systems. On the B-52D, the pilots and electronic countermeasures (ECM) operator ejected upwards, while the lower deck crew ejected downwards; until the B-52G, the gunner had to jettison the tail gun to bail out . The tail gunner in early model B-52s was located in the traditional location in the tail of the plane, with both visual and radar gun laying systems; in later models,

15548-490: The conclusions of a separate Congress-funded study conducted in 2003. Criticizing the USAF cost analysis, the DSB found that among other things, the USAF failed to account for the cost of aerial refueling; the DSB estimated that aerial refueling cost $ 17.50 per US gallon ($ 4.62/L), whereas the USAF had failed to account for the cost of delivering the fuel and so had only priced fuel at $ 1.20 per US gallon ($ 0.32/L). On 23 April 2020,

15717-638: The control surfaces, increasing drag . When the wing tips were drooped, the lifting area of the wings was lessened, moving the lift forward and reducing trim drag . The buildup of heat due to skin friction during sustained supersonic flight had to be addressed. During a Mach 3 cruise, the aircraft would reach an average of 450 °F (230 °C), with leading edges reaching 630 °F (330 °C), and up to 1,000 °F (540 °C) in engine compartments. NAA proposed building their design out of sandwich panels , with each panel consisting of two thin sheets of stainless steel brazed to opposite faces of

15886-404: The creation of prototypes will differ from creation of the final product in some fundamental ways: Engineers and prototype specialists attempt to minimize the impact of these differences on the intended role for the prototype. For example, if a visual prototype is not able to use the same materials as the final product, they will attempt to substitute materials with properties that closely simulate

16055-581: The crew. One update is the AN/ARC-210 Warrior beyond-line-of-sight software programmable radio able to transmit voice, data, and information in-flight between B-52s and ground command and control centers, allowing the transmission and reception of data with updated intelligence, mapping, and targeting information; previous in-flight target changes required copying down coordinates. The ARC-210 allows machine-to-machine transfer of data, useful on long-endurance missions where targets may have moved before

16224-523: The cruise missile-armed B-52Gs were modified with a distinctive wing root fairing . As all B-52Hs were assumed modified, no visual modification of these aircraft was required. In 1990, the stealthy AGM-129 ACM cruise missile entered service; although intended to replace the AGM-86, the high cost and the Cold War's end led to only 450 being produced; unlike the AGM-86, no conventional, non-nuclear version

16393-454: The crushing of his arm by the closing clamshell-like escape crew capsule moments prior to ejection. Prototype A prototype can also mean a typical example of something such as in the use of the derivation ' prototypical '. This is a useful term in identifying objects, behaviours and concepts which are considered the accepted norm and is analogous with terms such as stereotypes and archetypes . The word prototype derives from

16562-407: The cycle returns to customer evaluation. The cycle starts by listening to the user, followed by building or revising a mock-up, and letting the user test the mock-up , then back. There is now a new generation of tools called Application Simulation Software which help quickly simulate application before their development. Extreme programming uses iterative design to gradually add one feature at

16731-460: The day, and directed Boeing to use the turboprop-powered Model 464–35 as the basis for the XB-52. Although he agreed that turbojet propulsion was the future, General Howard A. Craig, Deputy Chief of Staff for Materiel, was not very enthusiastic about a jet-powered B-52 since he felt that the jet engine had not yet progressed sufficiently to permit skipping an intermediate turboprop stage. However, Boeing

16900-403: The design for the purposes of reducing costs through optimization and refinement. It is possible to use prototype testing to reduce the risk that a design may not perform as intended, however prototypes generally cannot eliminate all risk. Building the full design is often expensive and can be time-consuming, especially when repeated several times—building the full design, figuring out what

17069-409: The design. That resulted in the development of yet another revision—in July 1948, Model 464-40 substituted Westinghouse J40 turbojets for the turboprops. The USAF project officer who reviewed the Model 464-40 was favorably impressed, especially since he had already been thinking along similar lines. Nevertheless, the government was concerned about the high fuel consumption rate of the jet engines of

17238-544: The designs, and in September 1956 deemed them too large and complicated for operations. General Curtis LeMay was dismissive, declaiming, "This is not an airplane, it's a three-ship formation." The USAF ended Phase 1 development in October 1956 and instructed the two contractors to continue design studies. While the original proposals were being studied, advances in supersonic flight were proceeding rapidly. The narrow delta

17407-422: The desire for a cruising speed of 400 miles per hour (350 kn; 640 km/h), to which Boeing responded with a 300,000-pound (140,000 kg) aircraft. In December 1946, Boeing was asked to change their design to a four-engine bomber with a top speed of 400 miles per hour (350 kn; 640 km/h), range of 12,000 miles (10,000 nmi; 19,000 km), and the ability to carry a nuclear weapon ; in total,

17576-763: The earliest Soviet guided air-defence missiles, the S-75 Dvina , known in the west as the SA-2 Guideline. Faced with this problem, military doctrine had already started shifting away from high-altitude supersonic bombing toward low-altitude penetration . Radar is line-of-sight, so aircraft could dramatically shorten detection distances by flying close to the Earth and hiding behind terrain. Missile sites spaced to overlap in range when attacking bombers at high altitudes would leave large gaps between their coverage for bombers flying at lower levels. With an appropriate map of

17745-428: The eight Pratt & Whitney TF33 engines (total thrust 136,000 lbf (600 kN)) with four RB211-535E4 engines (total thrust 172,400 lbf (767 kN)), which would increase range and reduce fuel consumption. However, a USAF analysis in 1997 concluded that Boeing's estimated savings of US$ 4.7   billion would not be realized and that reengining would instead cost US$ 1.3   billion more than keeping

17914-410: The engine intake splitter below the apex of the wing. At Mach 3 cruising speed, the shock wave is bent back about 65 degrees and the wing is superimposed on the shock system which has a pressure 40 pounds per square foot (1.9 kPa) higher under the aircraft than in front of the shock. The compression lift provided five percent of the total lift. Camber was added to the wing leading edge inboard of

18083-422: The engines, better positioning the shock in relation to the wing. The six individually-podded engines were repositioned, three in each of two separate ducts, under the fuselage. North American improved on the basic concept by adding a set of drooping wing-tip panels that were lowered at high speed. This helped trap the shock wave under the wing between the downturned wing tips. It also added more vertical surface to

18252-517: The entire project was postponed for six months. During this time, Boeing continued to perfect the design, which resulted in the Model 464–29 with a top speed of 455 miles per hour (395 kn; 732 km/h) and a 5,000-mile (8,000 km) range. In September 1947, the Heavy Bombardment Committee was convened to ascertain performance requirements for a nuclear bomber. Formalized on 8 December 1947, these requirements called for

18421-402: The era did not have the ability to look down (see look-down/shoot-down ); if a higher altitude aircraft's radar was aimed down to detect targets at a lower altitude, the reflection of the ground would overwhelm the signal returned from a target. An interceptor flying at normal altitudes would be effectively blind to bombers far below it. The interceptor could descend to lower altitudes to increase

18590-454: The existing engines, citing significant up-front procurement and re-tooling expenditure. The USAF's 1997 rejection of reengining was subsequently disputed in a Defense Science Board (DSB) report in 2003. The DSB urged the USAF to re-engine the aircraft without delay, saying doing so would not only create significant cost savings but reduce greenhouse gas emissions and increase aircraft range and endurance; these conclusions were in line with

18759-489: The external pylons could. Thirty B-52Gs were further modified to carry up to 12 AGM-84 Harpoon anti-ship missiles each, while 12 B-52Gs were fitted to carry the AGM-142 Have Nap stand-off air-to-ground missile. When the B-52G was retired in 1994, an urgent scheme was launched to restore an interim Harpoon and Have Nap capability, the four aircraft being modified to carry Harpoon and four to carry Have Nap under

18928-566: The first Soviet surface-to-air missiles in the late 1950s put the near-invulnerability of the B-70 in doubt. In response, the US Air Force (USAF) began flying its missions at low level, where the missile radar's line of sight was limited by terrain. In this low-level penetration role, the B-70 offered little additional performance over the B-52 it was meant to replace, while being far more expensive with shorter range. Alternative missions were proposed, but these were of limited scope. With

19097-412: The first effective anti-aircraft missiles by the late 1950s changed this picture dramatically. Missiles could stand ready for immediate launch, eliminating operational delays like the time needed to get the pilot into the cockpit of a fighter. Guidance did not require wide-area tracking or calculation of an intercept course: a simple comparison of the time needed to fly to the altitude of the target returned

19266-509: The first flight to December 1961. But in late 1958 the service announced that this acceleration would not be possible due to lack of funding. In December 1958, a Phase II contract was issued. The mockup of the B-70 was reviewed by the Air Force in March 1959. Provisions for air-to-surface missiles and external fuel tanks were requested afterward. At the same time, North American was developing the F-108 supersonic interceptor. To reduce program costs,

19435-432: The folding tips to improve subsonic handling and reduce supersonic drag. The outer portions of the wings were hinged to pivot downward by 65 degrees, acting as a type of variable-geometry wingtip device . This increased the aircraft's directional stability at supersonic speeds, shifted the center of pressure to a more favorable position at high speeds, and caused the shock originating at the intake splitter to reflect from

19604-784: The formation. After the photoshoot, the F-104 drifted into the XB-70's right wingtip, flipped and rolled inverted over the top of the Valkyrie, before striking the bomber's vertical stabilizers and left wing. The F-104 then exploded, destroying the Valkyrie's vertical stabilizers and damaging its left wing. Despite the loss of both vertical stabilizers and damage to the wings, the Valkyrie flew straight for 16 seconds before it entered an uncontrollable spin and crashed north of Barstow, California . NASA Chief Test Pilot Joe Walker (F-104 pilot) and Carl Cross (XB-70 co-pilot) were killed. Al White (XB-70 pilot) ejected, sustaining serious injuries, including

19773-508: The full design. In technology research, a technology demonstrator is a prototype serving as proof-of-concept and demonstration model for a new technology or future product, proving its viability and illustrating conceivable applications. In large development projects, a testbed is a platform and prototype development environment for rigorous experimentation and testing of new technologies, components, scientific theories and computational tools. With recent advances in computer modeling it

19942-648: The future Long Range Stand Off (LRSO) nuclear -armed air-launched cruise missile will join the B-52 inventory in the future. The eight engines of the B-52 are paired in pods and suspended by four pylons beneath and forward of the wings' leading edge . The careful arrangement of the pylons also allowed them to work as wing fences and delay the onset of stall . The first two prototypes, XB-52 and YB-52, were both powered by experimental Pratt & Whitney YJ57-P-3 turbojet engines with 8,700 pounds-force (39 kN) of static thrust each. The B-52A models were equipped with Pratt & Whitney J57-P-1W turbojets, providing

20111-576: The gunner was moved to the front of the fuselage, with gun laying carried out by radar alone, much like the B-58 Hustler's tail gun system. Structural fatigue was accelerated by at least a factor of eight in a low-altitude flight profile over that of high-altitude flying, requiring costly repairs to extend service life. In the early 1960s, the three-phase High Stress program was launched to counter structural fatigue, enrolling aircraft at 2,000 flying hours. Follow-up programs were conducted, such as

20280-522: The huge production effort, with 41% of the airframe being built by subcontractors. The prototypes and all B-52A, B and C models (90 aircraft) were built at Seattle. Testing of aircraft built in Seattle caused problems due to jet noise, which led to the establishment of curfews for engine tests. Aircraft were ferried 150 miles (240 km) east on their maiden flights to Larson Air Force Base near Moses Lake , where they were fully tested. As production of

20449-436: The idea was to use the shock wave generated off the nose or other sharp points on the aircraft as a source of high-pressure air. By carefully positioning the wing in relation to the shock, the shock's high pressure could be captured on the bottom of the wing and generate additional lift. To take maximum advantage of this effect, they redesigned the underside of the aircraft to feature a large triangular intake area far forward of

20618-437: The intended final materials. Engineers and prototyping specialists seek to understand the limitations of prototypes to exactly simulate the characteristics of their intended design. Prototypes represent some compromise from the final production design. This is due to the skill and choices of the designer(s), and the inevitable inherent limitations of a prototype. Due to differences in materials, processes and design fidelity, it

20787-559: The intensity and signature of sonic booms for the National Sonic Boom Program. Testing was planned to cover a range of sonic boom overpressures on the ground similar to but higher than those anticipated from the proposed American SST . In 1966, AV-2 was selected for the program and was outfitted with test sensors. It flew the first sonic boom test on 6 June 1966, attaining a speed of Mach 3.05 at 72,000 ft (22,000 m). Two days later, AV-2 crashed following

20956-410: The last airplanes are expected to serve into the 2050s. On 23 November 1945, Air Materiel Command (AMC) issued desired performance characteristics for a new strategic bomber "capable of carrying out the strategic mission without dependence upon advanced and intermediate bases controlled by other countries". The aircraft was to have a crew of five or more turret gunners , and a six-man relief crew. It

21125-438: The latest designs; Soviet interceptors during the late 1950s could not intercept the high-altitude U-2 reconnaissance aircraft, despite its relatively low speeds. It was later discovered that flying faster also made radar detection much more difficult due to an effect known as the blip-to-scan ratio , and any reduction in tracking efficiency would further interfere with the operation and guidance of fighters. The introduction of

21294-444: The leading edge of the left wing missing. The first aircraft was limited to Mach 2.5 afterwards. On 8 June 1966, XB-70A No. 2 was in close formation with four other aircraft (an F-4 Phantom , an F-5 , a T-38 Talon , and an F-104 Starfighter ) for a photoshoot at the behest of General Electric, manufacturer of the engines of all five aircraft. A sixth aircraft, a Learjet 23 , had been contracted by General Electric to photograph

21463-522: The long journey from the US to USSR. The value was limited; the USAF's doctrine stressed that the primary reason for maintaining the bomber force in an era of ICBMs was that the bombers could remain in the air at long ranges from their bases and were thus immune to sneak attack. In this case, the higher speed would be used for only a short period of time between the staging areas and the Soviet coastline. Adding to

21632-453: The missile sites, the bombers could fly between and around the defenses. Additionally, early missiles generally flew unguided for a period of time before the radar systems were able to track the missile and start sending it guidance signals. With the SA-2 missile, this minimum altitude was roughly 2,000 feet (600 m). Flying at low level provided protection against fighters as well. Radars of

21801-463: The mission requirements. The engine was stated to be in the "30,000-pound class", but actually produced 28,000 lbf (120 kN) with afterburner and 19,900 lbf (89 kN) without afterburner. The Valkyrie used fuel for cooling; it was pumped through heat exchangers before reaching the engines. To reduce the likelihood of autoignition , nitrogen was injected into the JP-6 during refueling, and

21970-402: The negative 1-G load position to the positive 4-G load position." The flexible structure allowed "...the wing to flex during gust and maneuvering loads, thus relieving high-stress areas and providing a smoother ride." During a 3.5-G pullup, "The wingtips appeared about 35 degrees above level flight position." During ground testing on 29 November 1951, the XB-52's pneumatic system failed during

22139-440: The nose of AV-1 for measuring the response of the aircraft's stability augmentation system. AV-1 flew a total of 83 flights. The XB-70's last supersonic flight took place on 17 December 1968. On 4 February 1969, AV-1 took its final flight to Wright-Patterson Air Force Base for museum display (now the National Museum of the United States Air Force ). Flight data was collected on this subsonic trip. North American Rockwell completed

22308-545: The problem of flying at three times the speed of sound with an airframe potentially useful as a bomber." After Congress approved $ 290 million ($ 3 billion today) of B-70 "add-on" funds to the President's 12 May 1960 modified FY 1961 budget, the Administration decided on a "Planned Usage" of only $ 100 million ($ 1,020 million today) of these funds. The Department of Defense subsequently presented data to Congress that

22477-429: The problems are and how to solve them, then building another full design. As an alternative, rapid prototyping or rapid application development techniques are used for the initial prototypes, which implement part, but not all, of the complete design. This allows designers and manufacturers to rapidly and inexpensively test the parts of the design that are most likely to have problems, solve those problems, and then build

22646-429: The problems, the zip fuel program was canceled in 1959. After burning, the fuel turned into caustic and abrasive liquids and solids that increased wear on moving turbine engine components and were toxic, making servicing difficult. Although the B-70 was intended to use zip only in the afterburners, and thus avoid this problem, the enormous cost of the zip program for such limited gains led to its cancellation. This by itself

22815-541: The production of airliners. Production ended in 1962 with the B-52H, with 742 aircraft built, plus the original two prototypes. A proposed variant of the B-52H was the EB-52H, which would have consisted of 16 modified and augmented B-52H airframes with additional electronic jamming capabilities. This variant would have restored USAF airborne jamming capability that it lost on retiring the EF-111 Raven . The program

22984-411: The prototyping platform, or replace it with only the microcontroller chip and the circuitry that is relevant to their product. Prototype software is often referred to as alpha grade , meaning it is the first version to run. Often only a few functions are implemented, the primary focus of the alpha is to have a functional base code on to which features may be added. Once alpha grade software has most of

23153-507: The ramp raised into its high-speed position, the forebody was more streamlined. Rain removal and windshield anti-ice was accomplished by utilizing 600 °F (320 °C) bleed air from the engines. The lower forward section included a radar bay, and production machines were to be equipped with a refueling receptacle on the upper surface of the forward fuselage. The XB-70 was equipped with six General Electric YJ93 -GE-3 turbojet engines, which used JP-6 jet fuel, specially formulated for

23322-438: The real EMD GP38-2 locomotive—which is the prototype of Athearn 's (among other manufacturers) locomotive model. Technically, any non-living object can serve as a prototype for a model, including structures, equipment, and appliances, and so on, but generally prototypes have come to mean full-size real-world vehicles including automobiles (the prototype 1957 Chevy has spawned many models), military equipment (such as M4 Shermans,

23491-473: The reconnaissance and strike mission was "crazy" since the nuclear mission was to attack known production and military complexes, and emphasized that he saw no need for the B-70 since the ICBM is "a cheaper, more effective way of doing the same thing". Eisenhower also identified that the B-70 would not be in manufacturing until "eight to ten years from now" and "said he thought we were talking about bows and arrows at

23660-529: The removal of B61-7 and B83-1 gravity bombs from the B-52H's approved weapons configuration. Starting in 2016, Boeing is to upgrade the internal rotary launchers to the MIL-STD-1760 interface to enable the internal carriage of smart bombs, which previously could be carried only on the wings. While the B-1 Lancer has a larger theoretical maximum payload of 75,000 pounds (34,000 kg) compared to

23829-469: The required deflection . Missiles also had greater altitude capability than any aircraft and improving this to adapt to new aircraft was a low-cost development path. The US was aware of Soviet work in the field, and had reduced the expected operational lifetime of the U-2, knowing that it would become vulnerable to these missiles as they were improved. In 1960, a U-2 flown by Gary Powers was shot down by one of

23998-463: The required features integrated into it, it becomes beta software for testing of the entire software and to adjust the program to respond correctly during situations unforeseen during development. Often the end users may not be able to provide a complete set of application objectives, detailed input, processing, or output requirements in the initial stage. After the user evaluation, another prototype will be built based on feedback from users, and again

24167-459: The result being a circuit that is electrically identical to the design but not physically identical to the final product. Open-source tools like Fritzing exist to document electronic prototypes (especially the breadboard-based ones) and move toward physical production. Prototyping platforms such as Arduino also simplify the task of programming and interacting with a microcontroller . The developer can choose to deploy their invention as-is using

24336-509: The roll-out ceremony on 18 March 1954, Air Force Chief of Staff General Nathan Twining said: The long rifle was the great weapon of its day.   ... today this B-52 is the long rifle of the air age. The B-52B was followed by progressively improved bomber and reconnaissance variants, culminating in the B-52G and turbofan B-52H. To allow rapid delivery, production lines were set up both at its main Seattle factory and at Boeing's Wichita facility. More than 5,000 companies were involved in

24505-429: The same conclusion soon afterwards, with both the US and UK starting missile development programs before the war ended. The UK's Green Mace was one of the last attempts to develop a useful high-altitude AAA weapon, but its development ended in 1957. Interceptor aircraft with ever-improving performance remained the only effective anti-bomber weapons by the early 1950s, and even these were having problems keeping up with

24674-469: The successful contract bid in June 1946, the B-52 design evolved from a straight wing aircraft powered by six turboprop engines to the final prototype YB-52 with eight turbojet engines and swept wings . The B-52 took its maiden flight in April 1952. The B-52 has been in service with the USAF since 1955, and NASA from 1959 to 2007. Built to carry nuclear weapons for Cold War –era deterrence missions,

24843-455: The time, nuclear weapons weighed several tons, and the need to carry enough fuel to fly that payload from the continental United States to the Soviet Union demanded large bombers. Boeing and RAND also concluded that the aircraft would need supersonic speed to escape the blast of its bombs. The aviation industry had been studying this problem for some time. From the mid-1940s, there was interest in using nuclear-powered aircraft as bombers. In

25012-403: The understanding that it could be adapted for nuclear strikes. In June 1947, the military requirements were updated and the Model 464-17 met all of them except for the range. It was becoming obvious to the USAAF that, even with the updated performance, the XB-52 would be obsolete by the time it entered production and would offer little improvement over the Convair B-36 Peacemaker ; as a result,

25181-408: The upgrade would look like. The upgrades will also include improved communication systems, new pylons, new cockpit displays and the deletion of one crew station. The changes will carry the designation B-52J. The B-52 shared many technological similarities with the preceding B-47 Stratojet strategic bomber. The two aircraft used the same basic design, such as swept wings and podded jet engines, and

25350-399: The vertical tip surface giving additional compression lift. Like a number of other delta-wing aircraft designed for supersonic speeds (Concorde, Tu-144, FD2), the Valkyrie needed a feature to improve the pilot's view during nose-high low-speed flight and on the ground. An outer windshield and ramp, which could be lowered, was provided enabling viewing through the fixed cockpit windshield. With

25519-519: The wing to twist, undermining roll control. Six spoilerons on each wing are responsible for the majority of roll control. The late B-52G models eliminated the ailerons altogether and added an extra spoileron to each wing. Partly because of the lack of ailerons, the B-52G and H models were more susceptible to Dutch roll . Ongoing problems with avionics systems were addressed in the Jolly Well program, completed in 1964, which improved components of

25688-505: The winner and announced plans to purchase 650 engines (608 direct replacements and 42 spares), for US$ 2.6   billion. Unlike the previous re-engine proposal which also involved reducing the number of engines from eight to four, the F130 re-engine program maintains eight engines on the B-52. Although four-engine operation would be more efficient, retrofitting the airframe to operate with only four engines would involve additional changes to

25857-480: Was an essentially new airplane. The new design (464-49) built upon the basic layout of the B-47 Stratojet with 35-degree swept wings , eight engines paired in four underwing pods , and bicycle landing gear with wingtip outrigger wheels. A notable feature was the ability to pivot both fore and aft main landing gear up to 20° from the aircraft centerline to increase safety during crosswind landings (allowing

26026-448: Was built. The B-52 was to have been modified to utilize Northrop Grumman 's AGM-137 TSSAM weapon; however, the missile was canceled due to development costs. Those B-52Gs not converted as cruise missile carriers underwent a series of modifications to improve conventional bombing. They were fitted with a new Integrated Conventional Stores Management System (ICSMS) and new underwing pylons that could hold larger bombs or other stores than

26195-523: Was canceled in 2005 following the removal of funds for the stand-off jammer. The program was revived in 2007 and cut again in early 2009. In July 2013, the USAF began a fleet-wide technological upgrade of its B-52 bombers called Combat Network Communications Technology (CONECT) to modernize electronics, communications technology, computing, and avionics on the flight deck. CONECT upgrades include software and hardware such as new computer servers, modems, radios, data-links, receivers, and digital workstations for

26364-471: Was completed on 15 October 1964. The manufacture of the third prototype (AV-3) was canceled in July 1964 before completion. The first XB-70 carried out its maiden flight in September 1964 and many more test flights followed. The data from the XB-70 test flights and aerospace materials development were used in the later B-1 bomber program , the American supersonic transport (SST) program, and via espionage,

26533-552: Was depleted before a supersonic dash to the target. The tanks also included the outer portions of the wing, which would also be jettisoned to produce a smaller wing suitable for supersonic speeds. Both became trapezoidal wings after ejection, at that time the highest performance planform known. They also featured flush cockpits to maintain the highest fineness ratio possible in spite of its effects on visibility. The two designs had takeoff weights of about 750,000 pounds (340,000 kg) with large fuel loads. The Air Force evaluated

26702-414: Was encouraged to continue turbojet studies even without any expected commitment to jet propulsion. On Thursday, 21 October 1948, Boeing engineers George S. Schairer , Art Carlsen, and Vaughn Blumenthal presented the design of a four-engine turboprop bomber to the chief of bomber development, Colonel Pete Warden . Warden was disappointed by the projected aircraft and asked if the Boeing team could produce

26871-483: Was establishing itself as a preferred planform for supersonic flight, replacing earlier designs like the swept-wing and trapezoidal layouts seen on designs like the Lockheed F-104 Starfighter and the earlier WS-110 concepts. Engines able to cope with higher temperatures were also under development, allowing for sustained supersonic speeds. This work led to an interesting discovery: when an engine

27040-569: Was expected that the B-70 would be practically immune to interceptor aircraft , the only effective weapon against bomber aircraft at the time. The bomber would spend only a brief time over a particular radar station, flying out of its range before the controllers could position their fighters in a suitable location for an interception. Its high speed made the aircraft difficult to see on radar displays and its high-altitude and high-speed capabilities could not be matched by any contemporaneous Soviet interceptor or fighter aircraft. The introduction of

27209-602: Was flown with the undercarriage down as a precaution, limiting speed to 390 mph (630 km/h) – about half that planned. During landing, the rear wheels of the port side main gear locked, the tires ruptured, and a fire started. The Valkyrie first became supersonic (Mach 1.1) on the third test flight on 12 October 1964, and flew above Mach 1 for 40 minutes during the following flight on 24 October. The wing tips were also lowered partially in this flight. XB-70 No. 1 surpassed Mach 3 on 14 October 1965 by reaching Mach 3.02 at 70,000 ft (21,000 m). The first aircraft

27378-459: Was found to suffer from weaknesses in the honeycomb panels, primarily due to inexperience with fabrication and quality control of this new material. On two occasions, honeycomb panels failed and were torn off during supersonic flight, necessitating a Mach 2.5 limit being placed on the aircraft. The deficiencies discovered on AV-1 were almost completely solved on the second XB-70, which first flew on 17 July 1965. On 3 January 1966, XB-70 No. 2 attained

27547-408: Was informed that the missile gap was an illusion. On 28 March 1961, after $ 800 million (equivalent to $ 8.2 billion today) had been spent on the B-70 program, Kennedy canceled the project as "unnecessary and economically unjustifiable" because it "stood little chance of penetrating enemy defenses successfully." Instead, Kennedy recommended "the B-70 program be carried forward essentially to explore

27716-518: Was instructed to thoroughly explore recent technological innovations, including aerial refueling and the flying wing . Noting stability and control problems Northrop Corporation was experiencing with their YB-35 and YB-49 flying wing bombers, Boeing insisted on a conventional aircraft, and in April 1948 presented a US$ 30   million (US$ 380 million today ) proposal for design, construction, and testing of two Model 464-35 prototypes. Further revisions during 1948 resulted in an aircraft with

27885-505: Was later canceled in 1958 due to better options. In July 1955, six contractors were selected to bid on WS-110A studies. Boeing and North American Aviation submitted proposals, and on 8 November 1955 were awarded contracts for Phase 1 development. In mid-1956, initial designs were presented by the two companies. Zip fuel was to be used in the afterburners to improve range by 10 to 15 percent over conventional fuel. Both designs had huge wing-tip fuel tanks that could be jettisoned when their fuel

28054-493: Was not a fatal problem as newly developed high-energy fuels like JP-6 were available to make up some of the difference. Most of the range lost in the change from zip fuel was restored by filling one of the two bomb bays with a fuel tank. Another problem arose when the XF-108 program was canceled in September 1959, which ended the shared development that benefited the B-70 program. At two secret meetings on 16 and 18 November 1959,

28223-517: Was optimized specifically for high speed, it burned perhaps twice as much fuel at that speed than when it was running at subsonic speeds. However, the aircraft would be flying as much as four times as fast. Thus its most economical cruise speed, in terms of fuel per mile, was its maximum speed. This was entirely unexpected and implied that there was no point in the dash concept; if the aircraft was able to reach Mach 3, it may as well fly its entire mission at that speed. The question remained whether such

28392-530: Was reduced to only the two pilots, as a navigator and a bombardier were not needed for this research role. The production order was reduced to three prototypes in March 1961 with the third aircraft to incorporate improvements from the previous prototype. The order was later reduced to two experimental XB-70As, named Air Vehicle 1 and 2 (AV-1 and AV-2). XB-70 No. 1 was completed on 7   May 1964, and rolled out on 11   May 1964 at Palmdale, California . One report stated "nothing like it existed anywhere". AV-2

28561-612: Was required to cruise at 300 miles per hour (260 kn; 480 km/h) at 34,000 feet (10,000 m) with a combat radius of 5,000 miles (4,300 nmi; 8,000 km). The armament was to consist of an unspecified number of 20 mm cannons and 10,000 pounds (4,500 kg) of bombs. On 13 February 1946, the USAAF issued bid invitations for these specifications, with Boeing, Consolidated Aircraft , and Glenn L. Martin Company submitting proposals. On 5 June 1946, Boeing's Model 462,

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