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127-430: The Boom Overture is a proposed supersonic airliner under development by Boom Technology . Its design will be capable of traveling Mach  1.7 (1,000  kn ; 1,800  km/h ; 1,100  mph ), with 64–80 passengers depending on configuration, and 4,250 nmi (7,870 km; 4,890 mi) of range. The Overture is planned to be introduced in 2029. The company claims that with 500 viable routes, there could be

254-505: A whirling arm apparatus to determine drag and did some of the first experiments in aviation theory. Sir George Cayley (1773–1857) also used a whirling arm to measure the drag and lift of various airfoils. His whirling arm was 5 feet (1.5 m) long and attained top speeds between 10 and 20 feet per second (3 to 6 m/s). Otto Lilienthal used a rotating arm to accurately measure wing airfoils with varying angles of attack , establishing their lift-to-drag ratio polar diagrams, but

381-775: A 1,000- to 2,000-aircraft potential market over 10 years. Boom plans to target $ 5,000 fares for a New York-to-London round-trip, while the same on Concorde cost $ 20,000 adjusted for inflation ; it was its only profitable route. The same fuel burn enables fares similar to subsonic business class among other factors. For long-range routes like San Francisco–Tokyo and Los Angeles–Sydney, 30 lie-flat first-class seats could be proposed alongside 15 business-class seats. In March 2016, Richard Branson confirmed that Virgin Group held options for 10 aircraft, and Virgin Galactic 's subsidiary The Spaceship Company will aid in manufacturing and testing

508-505: A centrifugal blower in 1897, and determined the drag coefficients of flat plates, cylinders and spheres. Danish inventor Poul la Cour applied wind tunnels in his process of developing and refining the technology of wind turbines in the early 1890s. Carl Rickard Nyberg used a wind tunnel when designing his Flugan from 1897 and onwards. In a classic set of experiments, the Englishman Osborne Reynolds (1842–1912) of

635-543: A class, can supply increased fuel efficiency at supersonic speeds, even though their specific fuel consumption is greater at higher speeds. Because their speed over the ground is greater, this decrease in efficiency is less than proportional to speed until well above Mach 2, and the consumption per unit distance is lower. When Concorde was being designed by Aérospatiale – BAC , high bypass jet engines (" turbofan " engines) had not yet been deployed on subsonic aircraft. Had Concorde entered service against earlier designs like

762-473: A compromise in performance is chosen, often to the detriment of low speed flight. For example, Concorde had very high drag (a lift to drag ratio of about 4) at slow speed, but it travelled at high speed for most of the flight. Designers of Concorde spent 5000 hours optimizing the vehicle shape in wind tunnel tests to maximize the overall performance over the entire flightplan. The Boeing 2707 featured swing wings to give higher efficiency at low speeds, but

889-542: A controlled dive during a test flight at Edwards Air Force Base. The crew were William Magruder (pilot), Paul Patten (copilot), Joseph Tomich (flight engineer), and Richard H. Edwards (flight test engineer). This is the first supersonic flight by a civilian airliner. In total, 20 Concordes were built: two prototypes, two development aircraft and 16 production aircraft. Of the sixteen production aircraft, two did not enter commercial service and eight remained in service as of April 2003. All but two of these aircraft are preserved;

1016-418: A cylinder or an airfoil, an individual component of an aircraft, a small model of the vehicle, or, in the largest tunnels, even a full-sized vehicle. Different measurements can be taken from these tests. The aerodynamic forces on the entire object can be measured, or on individual components of it. The air pressure at different points can be measured with sensors. Smoke can be introduced into the airstream to show

1143-483: A factor), and so is not directly useful for accurate measurements. The air moving through the tunnel needs to be relatively turbulence-free and laminar . To correct this problem, closely spaced vertical and horizontal air vanes are used to smooth out the turbulent airflow before reaching the subject of the testing. Due to the effects of viscosity , the cross-section of a wind tunnel is typically circular rather than square, because there will be greater flow constriction in

1270-415: A few decades. These materials, such as carbon fibre and Kevlar are much stronger for their weight (important to deal with stresses) as well as being more rigid. As per-seat weight of the structure is much higher in an SST design, structural improvements would have led to a greater proportional improvement than the same changes in a subsonic aircraft. Higher fuel costs and lower passenger capacities due to

1397-497: A flexible strip. The strip is attached to the aerodynamic surface with tape, and it sends signals depicting the pressure distribution along its surface. Pressure distributions on a test model can also be determined by performing a wake survey , in which either a single pitot tube is used to obtain multiple readings downstream of the test model, or a multiple-tube manometer is mounted downstream and all its readings are taken. The aerodynamic properties of an object can not all remain

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1524-433: A guide and means of comparison, observing that no detectable ozone loss was evident from approximately 213 megatons of explosive energy being released in 1962, so therefore the equivalent amount of NOx from "1047" Concordes flying "10 hours a day", would likewise, not be unprecedented. In 1981 models and observations were still irreconcilable. More recent computer models in 1995 by David W. Fahey, an atmospheric scientist at

1651-449: A launch with engine selection, supply chain, production site. Development and certification of the airliner and its engine were estimated at $ 6 billion, requiring Series C investors. Enough money was raised in the B round of fundraising to be able to hit key milestones, including flying the demonstrator (XB-1) to prove the technology, building up an order backlog, finding key suppliers for engines, aerostructures, and avionics, and lay out

1778-639: A market for up to 1,000 supersonic airliners with fares similar to business class. The aircraft is planned to have a delta wing configuration (similar to Concorde ), but will be built with composite materials . Following a redesign revealed in 2022, it is intended to be powered by four dry (non- afterburning ) 35,000 lbf (160 kN) turbofans . The company says that five hundred daily routes would be viable: at Mach 1.7 over water, Newark and London would be 3 hours and 30 minutes apart; Newark and Frankfurt would be 4 hours apart. With 4,500 nmi (8,300 km) range, transpacific flights would require

1905-485: A mode of transport does not typically lead to such technological investments to increase the speed. Instead, the service providers prefer to compete in service quality and cost. An example of this phenomenon is high-speed rail . The speed limit of rail transport had been pushed so hard to enable it to effectively compete with road and air transport. But this achievement was not done for different rail operating companies to compete among themselves. This phenomenon also reduces

2032-584: A much stronger (and therefore heavier) structure because their fuselage must be pressurized to a greater differential than subsonic aircraft, which do not operate at the high altitudes necessary for supersonic flight. These factors together meant that the empty weight per seat of Concorde is more than three times that of a Boeing 747. Concorde and the TU-144 were both constructed of conventional aluminum: Concorde of Hiduminium and TU-144 of duralumin . Modern, advanced materials were not to come out of development for

2159-405: A pair of fans driven by 4,000 hp (3,000 kW) electric motors. The layout was a double-return, closed-loop format and could accommodate many full-size real aircraft as well as scale models. The tunnel was eventually closed and, even though it was declared a National Historic Landmark in 1995, demolition began in 2010. Until World War II, the world's largest wind tunnel, built in 1932–1934,

2286-437: A refueling stop: San Francisco and Tokyo would be 6 hours apart. There could be a market for 1,000 supersonic airliners by 2035. Boom targets a $ 200 million price, not discounted and excluding options and interior, in 2016 dollars. The company claims that operational costs per premium available seat mile will be lower than subsonic wide-body aircraft . The Boom factory will be sized to assemble up to 100 aircraft per year for

2413-562: A revised proposal for the production version of the Overture at the Farnborough Airshow . This version has four engines and a tailed delta wing. On December 13, 2022, Boom announced that it would develop its own turbofan engine after "Big Three" engine manufacturers Rolls-Royce , Pratt & Whitney and General Electric , as well as CFM and Safran previously declined to develop a new engine due to high capital costs. Named Symphony ,

2540-512: A second flight from Edinburgh , and a third which had taken off from Heathrow on a loop flight over the Bay of Biscay . By the end of the 20th century, projects like the Tupolev Tu-244 , Tupolev Tu-344 , SAI Quiet Supersonic Transport , Sukhoi-Gulfstream S-21 , High Speed Civil Transport , etc. had not been realized. For all vehicles traveling through air, the force of drag is proportional to

2667-480: A serious issue due to the high altitudes at which the planes flew, but experiments in the mid-1960s such as the controversial Oklahoma City sonic boom tests and studies of the USAF 's North American XB-70 Valkyrie proved otherwise (see Sonic boom § Abatement ). By 1964, whether civilian supersonic aircraft would be licensed was unclear, because of the problem. The annoyance of a sonic boom can be avoided by waiting until

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2794-620: A single return trip could be made per day, so the extra speed was not an advantage to the airline other than as a selling feature to its customers. The proposed American SSTs were intended to fly at Mach 3, partly for this reason. However, allowing for acceleration and deceleration time, a trans-Atlantic trip on a Mach 3 SST would be less than three times as fast as a Mach 1 trip. Since SSTs produce sonic booms at supersonic speeds they are rarely permitted to fly supersonic over land, and must fly supersonic over sea instead. Since they are inefficient at subsonic speeds compared to subsonic aircraft, range

2921-586: A slower Mach 1.7 cruise. In January 2022, Boom announced a grant of US$ 60m from the US Air Force ’s AFWERX program to further develop the Boom Overture supersonic airliner. In July 2022, Boom announced a partnership with Northrop Grumman to develop a 'special mission' variant for the U.S. Government and its allies. As of January 2022, the Overture's first flight is planned for 2026 with introduction into service expected in 2029. On July 19, 2022, Boom unveiled

3048-424: A speed increase. Also, for-profit companies generally prefer low risk business plans with high probabilities of appreciable profit, but an expensive leading-edge technological research and development program is a high-risk enterprise, as it is possible that the program will fail for unforeseeable technical reasons or will meet cost overruns so great as to force the company, due to financial resource limits, to abandon

3175-435: A supersonic aircraft needs to change with its speed for optimal performance. Thus, an SST would ideally change shape during flight to maintain optimal performance at both subsonic and supersonic speeds. Such a design would introduce complexity which increases maintenance needs, operations costs, and safety concerns. In practice all supersonic transports have used essentially the same shape for subsonic and supersonic flight, and

3302-524: A threat that was, in 1974, seemingly validated by an MIT team commissioned by the United States Department of Transportation . However, while many purely theoretical models were indicating the potential for large ozone losses from SST nitrogen oxides ( NOx ), other scientists in the paper " Nitrogen Oxides, Nuclear Weapon Testing , Concorde and Stratospheric Ozone " turned to historical ozone monitoring and atmospheric nuclear testing to serve as

3429-454: A typical wing design will cut its L/D ratio in half (e.g., Concorde managed a ratio of 7.14, whereas the subsonic Boeing 747 has an L/D ratio of 17). Because an aircraft's design must provide enough lift to overcome its own weight, a reduction of its L/D ratio at supersonic speeds requires additional thrust to maintain its airspeed and altitude. Jet engine design shifts significantly between supersonic and subsonic aircraft. Jet engines, as

3556-624: A vice president with Lockheed , stated to various magazines that an SST constructed of steel weighing 250,000 pounds (110,000 kg) could be developed for $ 160 million and in production lots of 200 or more sold for around $ 9 million. But it was the Anglo-French development of the Concorde that set off panic in the US industry, where it was thought that Concorde would soon replace all other long range designs, especially after Pan Am took out purchase options on

3683-431: A wind tunnel type of test during an actual flight in order to refine the computational model. Where external turbulent flow is present, CFD is not practical due to limitations in present-day computing resources. For example, an area that is still much too complex for the use of CFD is determining the effects of flow on and around structures, bridges, and terrain. The most effective way to simulative external turbulent flow

3810-421: Is a function of forward speed, which decreases from propellers, to fans, to no bypass at all as speed increases. Additionally, the large frontal area taken up by the low-pressure fan at the front of the engine increases drag, especially at supersonic speeds, and means the bypass ratios are much more limited than on subsonic aircraft. For example, the early Tu-144S was fitted with a low bypass turbofan engine which

3937-722: Is a particularly severe increase in drag around the sound barrier. Boom agrees that the fuel efficiency of the aircraft will be lower than subsonic competition, but states that operators of the aircraft "must use sustainable aviation fuel (SAF) and/or purchase high-quality carbon removal credits" to reduce the environmental impact. However, sustainable aviation fuel is not yet widely available, with large-scale production relying on technology that does not yet exist, and carbon-offsetting schemes have been widely criticized as being unable to deliver net-zero. Data from Boom General characteristics Performance Related development Related lists Supersonic transport Following

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4064-405: Is blown or sucked through a duct equipped with a viewing port and instrumentation where models or geometrical shapes are mounted for study. Typically the air is moved through the tunnel using a series of fans. For very large wind tunnels several meters in diameter, a single large fan is not practical, and so instead an array of multiple fans are used in parallel to provide sufficient airflow. Due to

4191-442: Is deteriorated and the number of routes that the aircraft can fly non-stop is reduced. This also reduces the desirability of such aircraft for most airlines. Supersonic aircraft have higher per-passenger fuel consumption than subsonic aircraft; this makes the ticket price necessarily higher, all other factors being equal, as well as making that price more sensitive to the price of oil. (It also makes supersonic flights less friendly to

4318-644: Is expected to not be louder at take-off than current airliners like the Boeing 777-300ER . Supersonic jets could be exempted from the FAA takeoff noise regulations, reducing their fuel consumption by 20–30% by using narrower engines optimized for acceleration over limiting noise. In 2017, Honeywell and NASA tested predictive software and cockpit displays showing the sonic booms en route , to minimize its disruption overland. Design changes announced in July 2022 included an increase in

4445-523: Is for understanding exhaust gas dispersion patterns for hospitals, laboratories, and other emitting sources. Other examples of boundary layer wind tunnel applications are assessments of pedestrian comfort and snow drifting. Wind tunnel modeling is accepted as a method for aiding in green building design. For instance, the use of boundary layer wind tunnel modeling can be used as a credit for Leadership in Energy and Environmental Design (LEED) certification through

4572-403: Is low at take-off, but is forced high during supersonic cruise. Transition between the two modes would occur at some point during the climb and back again during the descent (to minimize jet noise upon approach). The difficulty is devising a variable cycle engine configuration that meets the requirement for a low cross-sectional area during supersonic cruise. The sonic boom was not thought to be

4699-433: Is more efficient, it is still less efficient than flying subsonically. Another issue in supersonic flight is the lift to drag ratio (L/D ratio) of the wings. At supersonic speeds, airfoils generate lift in an entirely different manner than at subsonic speeds, and are invariably less efficient. For this reason, considerable research has been put into designing wing planforms for sustained supersonic cruise. At about Mach 2,

4826-486: Is not able to withstand temperatures much over 127 °C; above 127 °C the aluminium gradually loses its properties that were brought about by age hardening. For aircraft that have flown at Mach 3, materials such as stainless steel ( XB-70 Valkyrie , MiG-25 ) or titanium ( SR-71 , Sukhoi T-4 ) have been used. The range of an aircraft depends on three efficiencies which appear in the Breguet range equation. They are

4953-416: Is particularly important in open cockpit race cars such as Indycar and Formula One. Excessive lift forces on the helmet can cause considerable neck strain on the driver, and flow separation on the back side of the helmet can cause turbulent buffeting and thus blurred vision for the driver at high speeds. The advances in computational fluid dynamics (CFD) modelling on high-speed digital computers has reduced

5080-409: Is through the use of a boundary layer wind tunnel. There are many applications for boundary layer wind tunnel modeling. For example, understanding the impact of wind on high-rise buildings, factories, bridges, etc. can help building designers construct a structure that stands up to wind effects in the most efficient manner possible. Another significant application for boundary layer wind tunnel modeling

5207-477: The Boeing 707 or de Havilland Comet , it would have been much more competitive, though the 707 and DC-8 still carried more passengers. When these high bypass jet engines reached commercial service in the 1960s, subsonic jet engines immediately became much more efficient, closer to the efficiency of turbojets at supersonic speeds. One major advantage of the SST disappeared. Turbofan engines improve efficiency by increasing

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5334-413: The Boeing 747 carrying four times that, the speed and fuel advantages of the SST concept were taken away by sheer size. Another problem was that the wide range of speeds over which an SST operates makes it difficult to improve engines. While subsonic engines had made great strides in increased efficiency through the 1960s with the introduction of the turbofan engine with ever-increasing bypass ratios ,

5461-467: The National Oceanic and Atmospheric Administration , and others, suggest that the drop in ozone would be at most, "no more" than 1 to 2% if a fleet of 500 supersonic aircraft [were] operated. Fahey expressed that this would not be a fatal obstacle for an advanced SST development – while "a big caution flag...[it] should not be a showstopper for advanced SST development" because "removing the sulfur in

5588-548: The Tu-144 , which the western press nicknamed the "Concordski". The SST was seen as particularly offensive due to its sonic boom and the potential for its engine exhaust to damage the ozone layer . Both problems impacted the thinking of lawmakers, and eventually Congress dropped funding for the US SST program in March 1971, and all overland commercial supersonic flight was banned over

5715-520: The University of Manchester demonstrated that the airflow pattern over a scale model would be the same for the full-scale vehicle if a certain flow parameter were the same in both cases. This factor, now known as the Reynolds number , is a basic parameter in the description of all fluid-flow situations, including the shapes of flow patterns, the ease of heat transfer, and the onset of turbulence. This comprises

5842-409: The coefficient of drag ( C d ), to the square of the airspeed and to the air density. Since drag rises rapidly with speed, a key priority of supersonic aircraft design is to minimize this force by lowering the coefficient of drag. This gives rise to the highly streamlined shapes of SSTs. To some extent, supersonic aircraft also manage drag by flying at higher altitudes than subsonic aircraft, where

5969-577: The delta wing in most studies, including the Sud Aviation Super-Caravelle and Bristol Type 223 , although Armstrong-Whitworth proposed a more radical design, the Mach 1.2 M-Wing . Avro Canada proposed several designs to TWA that included Mach 1.6 double-ogee wing and Mach 1.2 delta-wing with separate tail and four under-wing engine configurations. Avro's team moved to the UK where its design formed

6096-417: The static pressure , and (for compressible flow only) the temperature rise in the airflow. The direction of airflow around a model can be determined by tufts of yarn attached to the aerodynamic surfaces. The direction of airflow approaching a surface can be visualized by mounting threads in the airflow ahead of and aft of the test model. Smoke or bubbles of liquid can be introduced into the airflow upstream of

6223-607: The 1960s, due to high supersonic wave drag implications. It also now features a small horizontal stabilizer. Due to the low 1.5 wing aspect ratio , low-speed drag is high, and the aircraft requires high thrust at take-off. Boom also needs to address the nose-up attitude on landing. Airframe maintenance costs are expected to be similar to those of other carbon fiber airliners. The Overture should have lower fuel burn than Concorde by relying on dry (no afterburner) engines, composite structures, and improved technology since Concorde's development, although until Overture flies, Concorde remains

6350-413: The 1960s, wind tunnel testing began to receive widespread adoption for automobiles , not so much to determine aerodynamic forces in the same way as an airplane, but to increase the fuel efficiency of vehicles by reducing the aerodynamic drag. In these studies, the interaction between the road and the vehicle plays a significant role, and this interaction must be taken into consideration when interpreting

6477-421: The Concorde. Congress was soon funding an SST design effort, selecting the existing Lockheed L-2000 and Boeing 2707 designs, to produce an even more advanced, larger, faster and longer ranged design. The Boeing 2707 design was eventually selected for continued work, with design goals of ferrying around 300 passengers and having a cruising speed near to Mach 3 . The Soviet Union set out to produce its own design,

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6604-536: The London–New York route in mind. The plane was allowed into Washington, D.C. (at Dulles in Virginia ), and the service was so popular that New Yorkers were soon complaining because they did not have it. It was not long before Concorde was flying into JFK . Along with shifting political considerations, the flying public continued to show interest in high-speed ocean crossings. This started additional design studies in

6731-425: The SST fleet would emit ~96 million metric tons of CO₂ per year (like American , Delta and Southwest combined in 2017), 1.6 to 2.4 gigatonnes of CO₂ over their 25-year lifetime: one-fifth of the international aviation carbon budget if aviation maintains its emissions share to stay under a 1.5 °C climate trajectory . Noise exposed area around airports could double compared to existing subsonic aircraft of

6858-519: The U.S. Green Building Council. Wind tunnel tests in a boundary layer wind tunnel allow for the natural drag of the Earth's surface to be simulated. For accuracy, it is important to simulate the mean wind speed profile and turbulence effects within the atmospheric boundary layer. Most codes and standards recognize that wind tunnel testing can produce reliable information for designers, especially when their projects are in complex terrain or on exposed sites. In

6985-466: The US, under the name "AST" (Advanced Supersonic Transport). Lockheed's SCV was a new design for this category, while Boeing continued studies with the 2707 as a baseline. By this time, the economics of past SST concepts were no longer reasonable. When first designed, the SSTs were envisioned to compete with long-range aircraft seating 80 to 100 passengers such as the Boeing 707 , but with newer aircraft such as

7112-415: The US. Presidential advisor Russell Train warned that a fleet of 500 SSTs flying at 65,000 ft (20 km) for a period of years could raise stratospheric water content by as much as 50% to 100%. According to Train, this could lead to greater ground-level heat and hamper the formation of ozone . Later, an additional threat to the ozone was hypothesized as a result of the exhaust's nitrogen oxides ,

7239-459: The United States as part of the plan to exploit German technology developments. For limited applications, computational fluid dynamics (CFD) can supplement or possibly replace the use of wind tunnels. For example, the experimental rocket plane SpaceShipOne was designed without any use of wind tunnels. However, on one test, flight threads were attached to the surface of the wings, performing

7366-403: The United States, many wind tunnels have been decommissioned from 1990 to 2010, including some historic facilities. Pressure is brought to bear on remaining wind tunnels due to declining or erratic usage, high electricity costs, and in some cases the high value of the real estate upon which the facility sits. On the other hand, CFD validation still requires wind-tunnel data, and this is likely to be

7493-584: The above, however, that they were simply using the accepted technology of the day, though this was not yet a common technology in America. In France , Gustave Eiffel (1832–1923) built his first open-return wind tunnel in 1909, powered by a 67 hp (50 kW) electric motor, at Champs-de-Mars, near the foot of the tower that bears his name. Between 1909 and 1912 Eiffel ran about 4,000 tests in his wind tunnel, and his systematic experimentation set new standards for aeronautical research. In 1912 Eiffel's laboratory

7620-405: The aerodynamic efficiency, which says how much wanted lift can be produced without too much unwanted drag, powerplant efficiency, which says how much fuel is converted into moving the aircraft against its drag resistance, and structural efficiency, which says how heavy the structure is compared to the fuel and passengers it can carry. Airlines potentially value very fast aircraft, because it enables

7747-524: The aerodynamic requirement for a narrow fuselage make SSTs an expensive form of commercial civil transportation compared with subsonic aircraft. For example, the Boeing 747 can carry more than three times as many passengers as Concorde while using approximately the same amount of fuel. Nevertheless, fuel costs are not the bulk of the price for most subsonic aircraft passenger tickets. For the transatlantic business market that SST aircraft were utilized for, Concorde

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7874-591: The air density is lower. As speeds approach the speed of sound, the additional phenomenon of wave drag appears. This is a powerful form of drag that begins at transonic speeds (around Mach 0.88 ). Around Mach 1, the peak coefficient of drag is four times that of subsonic drag. Above the transonic range, the coefficient drops drastically again, although remains 20% higher by Mach 2.5 than at subsonic speeds. Supersonic aircraft must have considerably more power than subsonic aircraft require to overcome this wave drag, and although cruising performance above transonic speed

8001-403: The air moved around it. In this way, a stationary observer could study the flying object in action, and could measure the aerodynamic forces acting on it. The development of wind tunnels accompanied the development of the airplane. Large wind tunnels were built during World War II, and as supersonic aircraft were developed, supersonic wind tunnels were constructed to test them. Wind tunnel testing

8128-644: The aircraft is at high altitude over water before reaching supersonic speeds; this was the technique used by Concorde. However, it precludes supersonic flight over populated areas. Supersonic aircraft have poor lift/drag ratios at subsonic speeds as compared to subsonic aircraft (unless technologies such as variable-sweep wings are employed), and hence burn more fuel, which results in their use being economically disadvantageous on such flight paths. Concorde had an overpressure of 1.94 lb/sq ft (93 Pa) (133 dBA SPL). Overpressures over 1.5 lb/sq ft (72 Pa) (131 dBA SPL) often cause complaints. If

8255-502: The aircraft spends a considerable amount of time in cruise. SST designs flying at least three times as fast as existing subsonic transports were possible, and would thus be able to replace as many as three planes in service, and thereby lower costs in terms of manpower and maintenance. Serious work on SST designs started in the mid-1950s, when the first generation of supersonic fighter aircraft were entering service. In Britain and France, government-subsidized SST programs quickly settled on

8382-495: The aircraft to make more flights per day, providing a higher return on investment. Also, passengers generally prefer faster, shorter-duration trips to slower, longer-duration trips, so operating faster aircraft can give an airline a competitive advantage, even to the extent that many customers will willingly pay higher fares for the benefit of saving time and/or arriving sooner. However, Concorde's high noise levels around airports, time zone issues, and insufficient speed meant that only

8509-413: The airline desirability of SSTs, because, for very long-distance transportation (a couple of thousand kilometers), competition between different modes of transport is rather like a single-horse race: air transport does not have a significant competitor. The only competition is between the airline companies, and they would rather pay moderately to reduce cost and increase service quality than pay much more for

8636-408: The amount of cold low-pressure air they accelerate, using some of the energy normally used to accelerate hot air in the classic non-bypass turbojet. The ultimate expression of this design is the turboprop , where almost all of the jet thrust is used to power a very large fan – the propeller . The efficiency curve of the fan design means that the amount of bypass that maximizes overall engine efficiency

8763-586: The answers out of a wind tunnel." In 1941 the US constructed one of the largest wind tunnels at that time at Wright Field in Dayton, Ohio. This wind tunnel starts at 45 feet (14 m) and narrows to 20 feet (6.1 m) in diameter. Two 40-foot (12 m) fans were driven by a 40,000 hp electric motor. Large scale aircraft models could be tested at air speeds of 400 mph (640 km/h). During WWII, Germany developed different designs of large wind tunnels to further their knowledge of aeronautics. For example,

8890-561: The basis of Hawker Siddeley 's designs. By the early 1960s, the designs had progressed to the point where the go-ahead for production was given, but costs were so high that the Bristol Aeroplane Company and Sud Aviation eventually merged their efforts in 1962 to produce Concorde. In the early 1960s, various executives of US aerospace companies were telling the US public and Congress that there were no technical reasons an SST could not be produced. In April 1960, Burt C Monesmith,

9017-624: The building will collapse. Determining such forces was required before building codes could specify the required strength of such buildings and these tests continue to be used for large or unusual buildings. Wind tunnel testing was first applied to automobiles as early as the 1920s, on cars such as the Rumpler Tropfenwagen , and later the Chrysler Airflow . Initially, automakers would test out scale models of their cars, but later, full scale automotive wind tunnels were built. Starting in

9144-489: The capability of reducing the boom by about half. Even lengthening the vehicle (without significantly increasing the weight) would seem to reduce the boom intensity (see Sonic boom § Abatement ). When it comes to public policy, for example, the FAA prohibits commercial airplanes from flying at supersonic speeds above sovereign land governed by the United States because of the negative impact the sonic boom brings to humans and animal populations below. The aerodynamic design of

9271-546: The case for the foreseeable future. Studies have been done and others are underway to assess future military and commercial wind tunnel needs, but the outcome remains uncertain. More recently an increasing use of jet-powered, instrumented unmanned vehicles, or research drones, have replaced some of the traditional uses of wind tunnels. The world's fastest wind tunnel as of 2019 is the LENS-X wind tunnel, located in Buffalo, New York. Air

9398-478: The central scientific justification for the use of models in wind tunnels to simulate real-life phenomena. However, there are limitations on conditions in which dynamic similarity is based upon the Reynolds number alone. The Wright brothers ' use of a simple wind tunnel in 1901 to study the effects of airflow over various shapes while developing their Wright Flyer was in some ways revolutionary. It can be seen from

9525-650: The certification process, with many special conditions but with precedents. At the June 2019 Paris Air Show , Boom CEO Blake Scholl announced the introduction of the Overture was delayed from 2023 to the 2025–2027 timeframe, following a two-year test campaign with six aircraft. In September 2020, the company announced it has been contracted by the United States Air Force to develop the Overture for possible use as Air Force One . On October 7, 2020, Boom publicly unveiled its XB-1 demonstrator, which it planned to fly for

9652-461: The company announced a radical redesign of Overture into a quadjet, to closely resemble the unsuccessful Boeing B-2707-300 design from the 1970s. A major change is that the new design features four large external engine pods rather than the two more compact engine 'box' nacelles, used on Concorde. This design has not been seen in high speed aircraft since the Convair B-58 Hustler bomber of

9779-438: The company had created concept drawings and wooden mockups of parts of the aircraft. In October 2016, the design was stretched to 155 ft (47 m) to seat up to 50 passengers with ten extra seats, its wingspan marginally increased, and a third engine was added to enable ETOPS with up to a 180 minutes diversion time. The plane could seat 55 passengers in a higher-density configuration. In June 2017, its introduction

9906-428: The corners of a square tunnel that can make the flow turbulent. A circular tunnel provides a smoother flow. The inside facing of the tunnel is typically as smooth as possible, to reduce surface drag and turbulence that could impact the accuracy of the testing. Even smooth walls induce some drag into the airflow, and so the object being tested is usually kept near the center of the tunnel, with an empty buffer zone between

10033-403: The demand for wind tunnel testing, but has not completely eliminated it. Many real-world problems can still not be modeled accurately enough by CFD to eliminate the need for physical tests in wind tunnels. Air velocity and pressures are measured in several ways in wind tunnels. Air velocity through the test section is determined by Bernoulli's principle . Measurement of the dynamic pressure ,

10160-414: The direction of smoke from a ship's stack, to whether a given airplane would fly. Progress at Aachen, I felt, would be virtually impossible without a good wind tunnel. When von Kármán began to consult with Caltech he worked with Clark Millikan and Arthur L. Klein. He objected to their design and insisted on a return flow making the device "independent of the fluctuations of the outside atmosphere". It

10287-742: The effort before it yields any marketable SST technology, causing potentially all investment to be lost. The International Council on Clean Transportation (ICCT) estimates a SST would burn 5 to 7 times as much fuel per passenger. The ICCT shows that a New York to London supersonic flight would consume more than twice as much fuel per passenger than in subsonic business-class , six times as much as for economy class , and three times as much as subsonic business for Los Angeles to Sydney. Designers can either meet existing environmental standards with advanced technology or lobby policymakers to establish new standards for SSTs. If there were 2,000 SSTs in 2035, there would be 5,000 flights per day at 160 airports and

10414-416: The end of the war, Germany had at least three different supersonic wind tunnels, with one capable of Mach 4.4 (heated) airflows. A large wind tunnel under construction near Oetztal , Austria would have had two fans directly driven by two 50,000 horsepower hydraulic turbines . The installation was not completed by the end of the war and the dismantled equipment was shipped to Modane , France in 1946 where it

10541-591: The engine will be conducted in partnership with Kratos subsidiary Florida Turbine Technologies for engine design, GE Aerospace subsidiary GE Additive for additive manufacturing consulting, and StandardAero for maintenance. FTT/KTT is currently a maker of microturbines for drones and cruise missiles. Boom aims for initial production of the engine to begin in 2024 at the Overture Superfactory at Greensboro, North Carolina . Drag increases (and therefore fuel efficiency decreases) with cruising speed, and there

10668-593: The engine will be developed under partnership with three entities: Kratos subsidiary Florida Turbine Technologies for engine design; StandardAero for maintenance ; and General Electric subsidiary GE Additive for consulting on printing components. Boom's original design for Overture was a trijet, which resembled a 75% scale model of Concorde and the XB-1 "Baby Boom" test vehicle was designed and built on this basis, which took its first flight in March 2024. However, in mid-2022,

10795-461: The environment and sustainability, two growing concerns of the general public, including air travelers.) Investing in research and development work to design a new SST can be considered as an effort to push the speed limit of air transport. Generally, other than an urge for new technological achievement, the major driving force for such an effort is competitive pressure from other modes of transport. Competition between different service providers within

10922-451: The fan concept is difficult to use at supersonic speeds where the "proper" bypass is about 0.45, as opposed to 2.0 or higher for subsonic designs. For both of these reasons the SST designs were doomed by higher operational costs, and the AST programs vanished by the early 1980s. Concorde only sold to British Airways and Air France, with subsidized purchases that were to return 80% of the profits to

11049-473: The first enclosed wind tunnel in 1871. Once this breakthrough had been achieved, detailed technical data was rapidly extracted by the use of this tool. Wenham and his colleague John Browning are credited with many fundamental discoveries, including the measurement of l/d ratios, and the revelation of the beneficial effects of a high aspect ratio . Konstantin Tsiolkovsky built an open-section wind tunnel with

11176-440: The first time in 2021 from Mojave Air and Space Port , California. It expected to begin wind tunnel tests for the Overture in 2021, and start construction of a manufacturing facility in 2022, with the capacity to produce 5 to 10 aircraft monthly. The first Overture would be unveiled in 2025, with the aim of achieving type certification by 2029. Flights should be available in 2030, as estimated by Blake Scholl. Boom currently targets

11303-441: The fuel of the [Concorde]" would essentially eliminate the hypothesized 1%–2% ozone-destruction-reaction-pathway. Despite the model-observation discrepancy surrounding the ozone concern, in the mid-1970s, six years after its first supersonic test flight, Concorde was now ready for service. The US political outcry was so high that New York banned the plane. This threatened the aircraft's economic prospects — it had been built with

11430-424: The government. In practice for almost all of the length of the arrangement, there was no profit to be shared. After Concorde was privatized, cost reduction measures (notably the closing of the metallurgical wing testing site which had done enough temperature cycles to validate the aircraft through to 2010) and ticket price raises led to substantial profits. Since Concorde stopped flying, it has been revealed that over

11557-547: The increased space required for such a feature produced capacity problems that proved ultimately insurmountable. North American Aviation had an unusual approach to this problem with the XB-70 Valkyrie . By lowering the outer panels of the wings at high Mach numbers, they were able to take advantage of compression lift on the underside of the aircraft. This improved the L/D ratio by about 30%. Aircraft are surrounded by an air layer

11684-407: The intensity of the boom can be reduced, then this may make even very large designs of supersonic aircraft acceptable for overland flight. Research suggests that changes to the nose cone and tail can reduce the intensity of the sonic boom below that needed to cause complaints. During the original SST efforts in the 1960s, it was suggested that careful shaping of the fuselage of the aircraft could reduce

11811-422: The intensity of the sonic boom's shock waves that reach the ground. One design caused the shock waves to interfere with each other, greatly reducing the sonic boom. This was difficult to test at the time, but the increasing power of computer-aided design has since made this considerably easier. In 2003, a Shaped Sonic Boom Demonstration aircraft was flown which proved the soundness of the design and demonstrated

11938-958: The jet. However, in 2023, Virgin Group announced that its purchase options had expired. An unnamed European carrier also holds options for 15 aircraft; the two deals total 5 billion dollars. At the 2017 Paris Air Show , 51 commitments were added for a backlog of 76 with significant deposits. In December 2017, Japan Airlines was confirmed to have pre-ordered up to 20 jets among the commitments to 76 from five airlines. Boom CEO Blake Scholl thinks 2,000 supersonic jets will connect 500 cities and one-way tickets between London and New York will be priced around £2,000, comparable with existing subsonic business class. On June 3, 2021, United Airlines announced it had signed an agreement to purchase 15 Overture aircraft with an additional 35 options, expecting to start passenger flights by 2029. On August 16, 2022, American Airlines announced an agreement to purchase 20 Overture aircraft with an additional 40 options. By March 2016,

12065-617: The life of Concorde, the plane did prove profitable, at least to British Airways. Concorde operating costs over nearly 28 years of operation were approximately £1 billion, with revenues of £1.75 billion. On 25 July 2000, Air France Flight 4590 crashed shortly after take-off with all 109 occupants and four on ground killed; the only fatal incident involving Concorde . Commercial service was suspended until November 2001, and Concorde aircraft were retired in 2003 after 27 years of commercial operations. The last regular passenger flights landed at London Heathrow on October 24, 2003, from New York ,

12192-593: The number of engines to four to allow for smaller less technically challenging engines and to allow takeoff at derated levels to lower noise, and redesigned gull form wing and fuselage to reduce drag . The Boom Symphony is planned as a two-spool medium-bypass turbofan engine for use on Overture. The engine is intended to produce 35,000 pounds (160 kN) of thrust at takeoff, sustain Overture supercruise at Mach 1.7, and burn sustainable aviation fuel exclusively. Boom announced in December 2022 that development of

12319-469: The object and the moving air. They are used to test the aerodynamic effects of aircraft , rockets , cars , and buildings . Different wind tunnels range in size from less than a foot across, to over 100 feet (30 m), and can have air that moves at speeds from a light breeze to hypersonic velocities. Usually, large fans move air through the wind tunnel, while the object being tested is held stationary. The object can be an aerodynamic test object such as

12446-453: The only Mach 2.0 supercruising aircraft in history and carried 30% more passengers than Boom is currently projecting. In 2017 the FAA and International Civil Aviation Organization (ICAO) were working on a sonic boom standard to allow supersonic flights overland. NASA plans to fly its Low Boom Flight Demonstrator for the first time in 2022 to assess public acceptability of a 75 PNLdB boom, lower than Concorde's 105 PNLdB. The Overture

12573-459: The path that air takes around the object. Or, small threads can be attached to specific parts to show the airflow at those points. The earliest wind tunnels were invented towards the end of the 19th century, in the early days of aeronautical research, as part of the effort to develop heavier-than-air flying machines. The wind tunnel reversed the usual situation. Instead of the air standing still and an aircraft moving, an object would be held still and

12700-453: The practice. SST engines need a fairly high specific thrust (net thrust/airflow) during supersonic cruise, to minimize engine cross-sectional area and, thereby, nacelle drag. Unfortunately this implies a high jet velocity, which makes the engines noisy, particularly at low speeds/altitudes and at take-off. Therefore, a future SST might well benefit from a variable cycle engine , where the specific thrust (and therefore jet velocity and noise)

12827-431: The pressure at each hole. Pressure distributions can more conveniently be measured by the use of pressure-sensitive paint , in which higher local pressure is indicated by lowered fluorescence of the paint at that point. Pressure distributions can also be conveniently measured by the use of pressure-sensitive pressure belts , a recent development in which multiple ultra-miniaturized pressure sensor modules are integrated into

12954-588: The same for a scaled model. However, by observing certain similarity rules, a very satisfactory correspondence between the aerodynamic properties of a scaled model and a full-size object can be achieved. The choice of similarity parameters depends on the purpose of the test, but the most important conditions to satisfy are usually: In certain particular test cases, other similarity parameters must be satisfied, such as e.g. Froude number . English military engineer and mathematician Benjamin Robins (1707–1751) invented

13081-556: The same size, with more than 300 operations per day at Dubai and London Heathrow , and over 100 in Los Angeles , Singapore , San Francisco , New York-JFK , Frankfurt , and Bangkok . Frequent sonic booms would be heard in Canada, Germany, Iraq, Ireland, Israel, Romania, Turkey, and parts of the United States, up to 150–200 per day or one every five minutes. On August 21, 1961, a Douglas DC-8-43 (registration N9604Z) exceeded Mach 1 in

13208-403: The sheer volume and speed of air movement required, the fans may be powered by stationary turbofan engines rather than electric motors. The airflow created by the fans that is entering the tunnel is itself highly turbulent due to the fan blade motion (when the fan is blowing air into the test section – when it is sucking air out of the test section downstream, the fan-blade turbulence is not

13335-591: The temperature of which increases with aircraft speed. As a result the skin of the aircraft gets hotter with increasing supersonic speeds (kinetic heating from the high speed boundary layer ). Heat from the sun also raises the skin temperature. Heat transfers into the aircraft structure which also gets hotter. By the early 1960s many investigations in the United States, Britain and France had shown equilibrium skin temperatures varying from 130 degC at Mach 2.2 to 330 degC at Mach 3. Subsonic aircraft are usually made of aluminium. However aluminium, while being light and strong,

13462-724: The termination of flying by Concorde, there have been no SSTs in commercial service. However, several companies have proposed supersonic business jet designs. Small SSTs have less environmental impact and design capability improves with continuing research which is aimed at producing an acceptable aircraft. Supersonic airliners have been the objects of numerous recent ongoing design studies. Drawbacks and design challenges are excessive noise generation (at takeoff and due to sonic booms during flight), high development costs, expensive construction materials, high fuel consumption, extremely high emissions, and an increased cost per seat over subsonic airliners. However, despite these challenges, Concorde

13589-426: The test model, and their path around the model can be photographed (see particle image velocimetry ). Aerodynamic forces on the test model are usually measured with beam balances , connected to the test model with beams, strings, or cables. The pressure distributions across the test model have historically been measured by drilling many small holes along the airflow path, and using multi-tube manometers to measure

13716-556: The test results. In the real world, the vehicle is moving while the road and air are stationary. In a wind tunnel test, the road must also be moved past a vehicle along with air being blown around it. This has been accomplished with moving belts under the test vehicle to simulate the moving road, and very similar devices are used in wind tunnel testing of aircraft take-off and landing configurations. Sporting equipment has also studied in wind tunnels, including golf clubs, golf balls, bobsleds, cyclists, and race car helmets. Helmet aerodynamics

13843-429: The thrust, leading to considerably greater fuel use. This effect is pronounced at speeds close to the speed of sound, as the aircraft is using twice the thrust to travel at about the same speed. The relative effect is reduced as the aircraft accelerates to higher speeds. Offsetting this increase in fuel use was the potential to greatly increase sortie rates of the aircraft, at least on medium and long-range flights where

13970-405: The two that are not are F-BVFD (cn 211), parked as a spare-parts source in 1982 and scrapped in 1994, and F-BTSC (cn 203), which crashed outside Paris on July 25, 2000, killing 100 passengers, 9 crew members, and 4 people on the ground. Wind tunnel Wind tunnels are machines in which objects are held stationary inside a tube, and air is blown around it to study the interaction between

14097-459: The wind stream is upwards for the testing of models in spin situations and the concepts and engineering designs for the first primitive helicopters flown in the US. Later research into airflows near or above the speed of sound used a related approach. Metal pressure chambers were used to store high-pressure air which was then accelerated through a nozzle designed to provide supersonic flow. The observation or instrumentation chamber ("test section")

14224-404: The wind tunnel at Peenemünde was a novel wind tunnel design that allowed for high-speed airflow research, but brought several design challenges regarding constructing a high-speed wind tunnel at scale. However, it successfully used some large natural caves which were increased in size by excavation and then sealed to store large volumes of air which could then be routed through the wind tunnels. By

14351-565: The world at that time at the Washington Navy Yard. The inlet was almost 11 feet (3.4 m) in diameter and the discharge part was 7 feet (2.1 m) in diameter. A 500 hp (370 kW) electric motor drove the paddle type fan blades. In 1931 the NACA built a 30 by 60 feet (9.1 by 18.3 m) full-scale wind tunnel at Langley Research Center in Hampton, Virginia. The tunnel was powered by

14478-545: Was Theodore von Kármán 's teacher at Göttingen University and suggested the construction of a wind tunnel for tests of airships they were designing. The vortex street of turbulence downstream of a cylinder was tested in the tunnel. When he later moved to Aachen University he recalled use of this facility: I remembered the wind tunnel in Göttingen was started as a tool for studies of Zeppelin behavior, but that it had proven to be valuable for everything else from determining

14605-440: Was actually very successful, and was able to sustain a higher ticket price. Now that commercial SST aircraft have stopped flying, it has become clearer that Concorde made substantial profit for British Airways. Extreme jet velocities used during take-off caused Concorde and Tu-144s to produce significant take-off noise. Communities near the airport were affected by high engine noise levels, which prompted some regulators to disfavor

14732-454: Was an arrangement followed by a number of wind tunnels later built; in fact the open-return low-speed wind tunnel is often called the Eiffel-type wind tunnel. Subsequent use of wind tunnels proliferated as the science of aerodynamics and discipline of aeronautical engineering were established and air travel and power were developed. The US Navy in 1916 built one of the largest wind tunnels in

14859-440: Was claimed to have operated profitably. Throughout the 1950s an SST looked possible from a technical standpoint, but it was not clear if it could be made economically viable. Because of differences in lift generation, aircraft operating at supersonic speeds have approximately one-half the lift-to-drag ratio of subsonic aircraft. This implies that for any given required amount of lift, the aircraft will have to supply about twice

14986-513: Was completed in 1930 and used for Northrop Alpha testing. In 1939 General Arnold asked what was required to advance the USAF, and von Kármán answered, "The first step is to build the right wind tunnel." On the other hand, after the successes of the Bell X-2 and prospect of more advanced research, he wrote, "I was in favor of constructing such a plane because I have never believed that you can get all

15113-488: Was considered of strategic importance during the Cold War for development of aircraft and missiles. Other problems are also studied with wind tunnels. The effects of wind on man-made structures need to be studied when buildings became tall enough to be significantly affected by the wind. Very tall buildings present large surfaces to the wind, and the resulting forces have to be resisted by the building's internal structure or else

15240-542: Was lacking the notions of induced drag and Reynolds numbers . However, the whirling arm does not produce a reliable flow of air impacting the test shape at a normal incidence. Centrifugal forces and the fact that the object is moving in its own wake mean that detailed examination of the airflow is difficult. Francis Herbert Wenham (1824–1908), a Council Member of the Aeronautical Society of Great Britain , addressed these issues by inventing, designing and operating

15367-451: Was located in a suburb of Paris, Chalais-Meudon , France. It was designed to test full-size aircraft and had six large fans driven by high powered electric motors. The Chalais-Meudon wind tunnel was used by ONERA under the name S1Ch until 1976 in the development of, e.g., the Caravelle and Concorde airplanes. Today, this wind tunnel is preserved as a national monument. Ludwig Prandtl

15494-412: Was moved to Auteuil, a suburb of Paris, where his wind tunnel with a two-metre test section is still operational today. Eiffel significantly improved the efficiency of the open-return wind tunnel by enclosing the test section in a chamber, designing a flared inlet with a honeycomb flow straightener and adding a diffuser between the test section and the fan located at the downstream end of the diffuser; this

15621-645: Was much less efficient than Concorde's turbojets in supersonic flight. The later TU-144D featured turbojet engines with comparable efficiency. These limitations meant that SST designs were not able to take advantage of the dramatic improvements in fuel economy that high bypass engines brought to the subsonic market, but they were already more efficient than their subsonic turbofan counterparts. Supersonic vehicle speeds demand narrower wing and fuselage designs, and are subject to greater stresses and temperatures. This leads to aeroelasticity problems, which require heavier structures to minimize unwanted flexing. SSTs also require

15748-425: Was poured on 22 June 1942 on a site that eventually would become Calspan , where the wind tunnel still operates. By the end of World War II, the US had built eight new wind tunnels, including the largest one in the world at Moffett Field near Sunnyvale, California, which was designed to test full size aircraft at speeds of less than 250 mph (400 km/h) and a vertical wind tunnel at Wright Field, Ohio, where

15875-465: Was re-erected and is still operated there by the ONERA . With its 26 ft (8 m) test section and airspeed up to Mach 1, it is the largest transonic wind tunnel facility in the world. Frank Wattendorf reported on this wind tunnel for a US response. On 22 June 1942, Curtiss-Wright financed construction of one of the nation's largest subsonic wind tunnels in Buffalo, NY. The first concrete for building

16002-425: Was scheduled for 2023. By July 2018, it was delayed to 2025. At the time, it had undergone over 1,000 simulated wind tunnel tests. Boom initially targeted a Mach 2.2 cruise speed to fit with transoceanic airline timetables and allow higher utilization, while keeping airport noise to Stage 4 , similar to subsonic long-range aircraft. The plane configuration was intended to be locked in late 2019 to early 2020 for

16129-543: Was then placed at the proper location in the throat or nozzle for the desired airspeed. In the United States, concern over the lagging of American research facilities compared to those built by the Germans led to the Unitary Wind Tunnel Plan Act of 1949, which authorized expenditure to construct new wind tunnels at universities and at military sites. Some German war-time wind tunnels were dismantled for shipment to

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