Boeing X-51 Waverider
The Boeing X-51 Waverider is an unmanned research scramjet experimental aircraft for hypersonic flight at Mach 5 and an altitude of 70,000 feet. The aircraft was designated X-51 in 2005, it completed its first powered hypersonic flight on 26 May 2010. After two unsuccessful test flights, the X-51 completed a flight of over six minutes and reached speeds of over Mach 5 for 210 seconds on 1 May 2013 for the longest duration powered hypersonic flight. Waverider refers in general to aircraft that take advantage of compression lift produced by their own shock waves; the X-51 program was a cooperative effort by the United States Air Force, DARPA, NASA, Pratt & Whitney Rocketdyne. The program was managed by the Aerospace Systems Directorate within the U. S. Air Force Research Laboratory. X-51 technology is proposed for use in the High Speed Strike Weapon, a Mach 5+ missile which could enter service in the mid-2020s. In the 1990s, the Air Force Research Laboratory began the HyTECH program for hypersonic propulsion.
Pratt & Whitney received a contract from the AFRL to develop a hydrocarbon-fueled scramjet engine which led to the development of the SJX61 engine. The SJX61 engine was meant for the NASA X-43C, canceled; the engine was applied to the AFRL's Scramjet Engine Demonstrator program in late 2003. The scramjet flight test vehicle was designated X-51 on 27 September 2005. In flight demonstrations, the X-51 is carried by a B-52 to an altitude of about 50,000 feet and released over the Pacific Ocean; the X-51 is propelled by an MGM-140 ATACMS solid rocket booster to Mach 4.5. The booster is jettisoned and the vehicle's Pratt & Whitney Rocketdyne SJY61 scramjet accelerates it to a top flight speed near Mach 6; the X-51 uses JP-7 fuel for the SJY61 scramjet. DARPA once viewed X-51 as a stepping stone to Blackswift, a planned hypersonic demonstrator, canceled in October 2008. In May 2013, the U. S. Air Force planned to apply X-51 technology to the High Speed Strike Weapon, a missile similar in size to the X-51.
The HSSW could enter service in the mid-2020s. It is envisioned to have a range of 500-600 nmi, fly at Mach 5-6, fit on an F-35 or in the internal bay of a B-2 bomber. Ground tests of the X-51A began in late 2005. A preliminary version of the X-51, the "Ground Demonstrator Engine No. 2", completed wind tunnel tests at the NASA Langley Research Center on 27 July 2006. Testing continued there until a simulated X-51 flight at Mach 5 was completed on 30 April 2007; the testing is intended to observe acceleration between Mach 4 and Mach 6 and to demonstrate that hypersonic thrust "isn't just luck". Four captive test flights were planned for 2009. However, the first captive flight of the X-51A on a B-52 was conducted on 9 December 2009, with further flights in early 2010; the first powered flight of the X-51 was planned for 25 May 2010, but the presence of a cargo ship traveling through a portion of the Naval Air Station Point Mugu Sea Range caused a 24-hour delay. The X-51 completed its first powered flight on 26 May 2010.
It flew for over 200 seconds. The test had the longest hypersonic flight time of 140 seconds while under its scramjet power; the X-43 had the previous longest flight burn time of 12 seconds, while setting a new speed record of Mach 9.68. Three more test flights were used the same flight trajectory. Boeing proposed to the Air Force Research Laboratory that two test flights be added to increase the total to six, with flights taking place at four to six week intervals, provided there are no failures; the second test flight was scheduled for 24 March 2011, but was not conducted due to unfavorable test conditions. The flight took place on 13 June 2011. However, the flight over the Pacific Ocean ended early due to an inlet unstart event after being boosted to Mach 5 speed; the flight data from the test was being investigated. A B-52 released the X-51 at an approximate altitude of 50,000 feet; the X-51's scramjet engine did not properly transition to JP-7 fuel operation. The third test flight took place on 14 August 2012.
The X-51 was to make a 300-second experimental flight at speeds of Mach 5. After separating from its rocket booster, the craft crashed into the Pacific; the Air Force Research Laboratory determined the problem was the X-51's upper right aerodynamic fin unlocked during flight and became uncontrollable. The aircraft lost control. On 1 May 2013, the X-51 performed its first successful flight test on its fourth test flight; the X-51 and booster was powered to Mach 4.8 by the booster rocket. It separated cleanly from the booster and ignited its own engine; the test aircraft accelerated to Mach 5.1 and flew for 210 seconds until running out of fuel and plunging into the Pacific Ocean off Point Mugu for over six minutes of total flight time. Researchers collected telemetry data for 370 seconds of flight; the test signified the completion of the program. The Air Force Research Laboratory believes the successful flight will serve as research for practical applications of hypersonic flight, such as a missile, transport, a
Sound barrier
The sound barrier or sonic barrier is the sudden increase in aerodynamic drag and other undesirable effects experienced by an aircraft or other object when it approaches the speed of sound. When aircraft first began to be able to reach close to the speed of sound, these effects were seen as constituting a barrier making faster speeds difficult or impossible; the term sound barrier is still sometimes used today to refer to aircraft reaching supersonic flight. In dry air at 20 °C, the speed of sound is 343 metres per second; the term came into use during World War II when pilots of high-speed fighter aircraft experienced the effects of compressibility, a number of adverse aerodynamic effects that deterred further acceleration impeding flight at speeds close to the speed of sound. These difficulties represented a barrier to flying at faster speeds. In 1947 it was demonstrated that safe flight at the speed of sound was achievable in purpose-designed aircraft thereby breaking the barrier. By the 1950s new designs of fighter aircraft reached the speed of sound, faster.
Some common whips such as the bullwhip or stockwhip are able to move faster than sound: the tip of the whip exceeds this speed and causes a sharp crack—literally a sonic boom. Firearms made after the 19th century have had a supersonic muzzle velocity; the sound barrier may have been first breached by living beings some 150 million years ago. Some paleobiologists report that, based on computer models of their biomechanical capabilities, certain long-tailed dinosaurs such as Apatosaurus and Diplodocus may have been able to flick their tails at supersonic speeds, creating a cracking sound; this finding is theoretical and disputed by others in the field. Meteors entering the Earth's atmosphere if not always, descend faster than sound; the tip of the propeller on many early aircraft may reach supersonic speeds, producing a noticeable buzz that differentiates such aircraft. This is undesirable, as the transonic air movement creates disruptive turbulence, it is due to these effects that propellers are known to suffer from decreased performance as they approach the speed of sound.
It is easy to demonstrate that the power needed to improve performance is so great that the weight of the required engine grows faster than the power output of the propeller can compensate. This problem was one that led to early research into jet engines, notably by Frank Whittle in England and Hans von Ohain in Germany, who were led to their research in order to avoid these problems in high-speed flight. Propeller aircraft were able to approach the critical Mach number in a dive. Doing so led to numerous crashes for a variety of reasons. Most infamously, in the Mitsubishi Zero, pilots flew at full power into the terrain because the increasing forces acting on the control surfaces of their aircraft overpowered them. In this case, several attempts to fix it only made the problem worse; the flexing caused by the low torsional stiffness of the Supermarine Spitfire's wings caused them, in turn, to counteract aileron control inputs, leading to a condition known as control reversal. This was solved in models with changes to the wing.
Worse still, a dangerous interaction of the airflow between the wings and tail surfaces of diving Lockheed P-38 Lightnings made "pulling out" of dives difficult. Flutter due to the formation of shock waves on curved surfaces was another major problem, which led most famously to the breakup of de Havilland Swallow and death of its pilot, Geoffrey de Havilland, Jr. in 1946. A similar problem is thought to have been the cause of the 1943 crash of the BI-1 rocket aircraft in the Soviet Union. All of these effects, although unrelated in most ways, led to the concept of a "barrier" making it difficult for an aircraft to exceed the speed of sound. Erroneous news reports caused most people to envision the sound barrier as a physical "wall", which supersonic aircraft needed to "break" with a sharp needle nose on the front of the fuselage. Rocketry and artillery experts' products exceeded Mach 1, but aircraft designers and aerodynamic engineers during and after World War II discussed Mach 0.7 as a limit dangerous to exceed.
During WWII and thereafter, a number of claims were made that the sound barrier had been broken in a dive. The majority of these purported events can be dismissed as instrumentation errors; the typical airspeed indicator uses air pressure differences between two or more points on the aircraft near the nose and at the side of the fuselage, to produce a speed figure. At high speed, the various compression effects that lead to the sound barrier cause the ASI to go non-linear and produce inaccurately high or low readings, depending on the specifics of the installation; this effect became known as "Mach jump". Before the introduction of Mach meters, accurate measurements of supersonic speeds could only be made externally using ground-based instruments. Many claims of supersonic speeds were found to be far below this speed when measured in this fashion. In 1942, Republic Aviation issued a press release stating that Lts. Harold E. Comstock and Roger Dyar had exceeded the speed of sound during test dives in the P-47 Thunderbolt.
It is agreed that this was due to inaccurate ASI readings. In similar tests, the North American P-51 Mustang, a higher performance aircraft, demonstrated limits at Mach 0.85, with every flight over M0.84 causing the aircraft to be damaged by vibration. One of the highest recorded instrumented Mach numbers attained for a propeller
Mach 2 (film)
Mach 2 is a 2001 American direct-to-video action disaster thriller film directed by Fred Olen Ray. It was the first film to feature the airliner Concorde being hijacked. U. S. Senator Stuart Davis, running against the Vice-President, plans a trip to the Balkans to negotiate the release of American servicemen being held hostage by terrorists. Before he leaves, he receives a disk documenting evidence that the Vice-President has been trying to revive the American economy by causing a war in the Balkans, he announces his plans at Washington Dulles International Airport to show it to both sides in the hopes of ending the situation. He boards Concorde flight 209 to Paris along with some Air Force Officers and news employees. Unexpected Secret Service agents board the Concorde. After takeoff, the secret service agents led by Barry Rogers, shoot an Air Force officer and his men hijack the Concorde in mid-flight. Barry takes Stuart and the others hostage and forces him to hand over the disk in order to prevent the war being averted.
In the cockpit, Barry announces to the Dulles International Airport air traffic controller that the agents are armed with a nuclear device and threaten to crash the Concorde into Paris. Air Force Officer, Jack Tyree, arrives at the cockpit, where Stuart is held hostage, overpowers one of Barry's men, accidentally shooting the co-pilot in the process. Jack helps fly the Concorde and frees Stuart. Another agent arrives and shoots Captain Roman and takes Jack hostage. Having brought with them two pairs of parachutes, the men jump off the plane, after revealing that there was no nuclear device aboard the aircraft; the two men escape along some cliffs. Elsewhere, two French Secret Service Agents that have overheard the hijacking, chase Rogers and his men down the road towards a pre-prepared road block. Rogers sets an electromagnetic pulse bomb to destroy the French car, until the officer at the roadblock fires a shell at the agents, they skid off the road, violently roll down the cliffs and break up, killing Barry and his men instantly.
On the Concorde and news employee Shannon Carpenter attempt to fly the Concorde but Jack can't fly an aircraft and is nicknamed "washout". The aircraft's radio is damaged due to the previous fight with one of Barry's men. Since Shannon is a former mechanic, she repairs the radio and restores contact with Paris Air Traffic control. Meanwhile, with it having been rumoured that the agents planted a nuclear device on the Concorde, Dulles air traffic control orders a nearby aircraft carrier to launch a fighter aircraft to intercept the Concorde before it reaches Paris. On the aircraft, Shannon announces to Dulles and Paris Orly airport that there is no device on the aircraft, she manages to order the fighter to abort, after two near misses from its missiles. Because of the explosion of a nearby missile fired from the fighter, the Concorde's fuel line is torn and is leaking fuel, compromising the arrival at Paris. With the plane low on fuel, Jack, is instructed via radio to land the Concorde at the airport.
The landing is successful and the passengers depart safely. Shannon, having hidden the actual disk in the trash, hands over the disk containing confidential files to Stuart, making it possible for the war to be averted. Jack and Shannon engage in a passionate kiss and the film ends, displaying the Concorde. Brian Bosworth... Jack Tyree, an air force officer. Shannon Whirry... Shannon Carpenter, a former mechanic and news employee. Cliff Robertson... Vice President Pike Bruce Weitz... Phil Jefferson Robert Pine... Captain Roman Andrew Stevens... Commander Stevens Michael Dorn... Barry Rogers, leader of the Secret Service team that hijack the Concorde. David Hedison... Senator Stuart Davis, a presidential candidate. Jennifer Hammon... Gina Kendall John Putch... Tim Mandell, a news employee Charles Cyphers... Harry Olson Ron Chaney... Captain Wallace Sondra Currie... Courtney Davis, Stuart Davis' wife Lance Guest... Keith Dorman, a passenger Austin Stoker... Edwards Jan Speck... Linda Carson Ai Wan... Wendy Carson Tom Simmons...
Ted Nikki Fritz... Jill Peter Looney... Agent George Curtis Grant Cramer... Agent Lyndon Richard Partlow... Jefferson Baker, Jack Tyree's old friend and one of the agents. Richard Gabai... Co Pilot The scenes of the Concorde were used from the 1979 film The Concorde... Airport'79; the interior was a full scale set replica of a Boeing 747's cabin, making the interior appear larger on the inside than the outside. If the cabin on the real Concorde was that size, its total length would have been over 120 meters and a total wingspan of at least 50 meters; the scenes of the control tower was an aerodrome control tower, not the tower from the actual Washington Dulles International Airport, as seen because of its low height and small size. On the Concorde, there were many scenes of the United States Presidential Seal on the cabin divider walls. Several movie errors were shown: the steering column shown onscreen is a vertical type, unlike Concorde's one is shaped like the letter "m", it features advanced LCD primary flight displays, but Concorde's display is just dials or analog style.
Mach 2 on IMDb Mach 2 at Rotten Tomatoes Mach 2 at the TCM Movie Database New info on Scenery reference is https://www.imdb.com/title/tt0222020/trivia?tab=gf&ref_=tt_trv_gf
Canard (aeronautics)
A canard is an aeronautical arrangement wherein a small forewing or foreplane is placed forward of the main wing of a fixed-wing aircraft. The term "canard" may be used to describe the aircraft itself, the wing configuration or the foreplane. Despite the use of a canard surface on the first powered aeroplane, the Wright Flyer of 1903, canard designs were not built in quantity until the appearance of the Saab Viggen jet fighter in 1967; the aerodynamics of the canard configuration require careful analysis. Rather than use the conventional tailplane configuration found on most aircraft, an aircraft designer may adopt the canard configuration to reduce the main wing loading, to better control the main wing airflow, or to increase the aircraft’s maneuverability at high angles of attack or during a stall. Canard foreplanes, whether used in a canard or three-surface configuration, have important consequences on the aircraft’s longitudinal equilibrium and dynamic stability characteristics; the term “canard” arose from the appearance of the Santos-Dumont 14-bis of 1906, said to be reminiscent of a duck with its neck stretched out in flight.
The Wright Brothers began experimenting with the foreplane configuration around 1900. Their first kite included a front surface for pitch control and they adopted this configuration for their first Flyer, they were suspicious of the aft tail. The Wrights realised that a foreplane would tend to destabilise an aeroplane but expected it to be a better control surface, in addition to being visible to the pilot in flight, they believed it impossible to provide both control and stability in a single design, opted for control. Many pioneers followed the Wrights' lead. For example, the Santos-Dumont 14-bis aeroplane of 1906 had no "tail", but a box kite-like set of control surfaces in the front, pivoting on a universal joint on the fuselage's extreme nose, making it capable of incorporating both yaw and pitch control; the Fabre Hydravion of 1910 had a foreplane. But canard behaviour was not properly understood and other European pioneers—among them, Louis Blériot—were establishing the tailplane as the safer and more "conventional" design.
Some, including the Wrights, experimented with both fore and aft planes on the same aircraft, now known as the three surface configuration. After 1911, few canard types would be produced for many decades. In 1914 W. E. Evans commented that "the Canard type model has received its death-blow so far as scientific models are concerned." Experiments continued sporadically for several decades. In 1917 de Bruyère constructed his C 1 biplane fighter, having a canard foreplane and rear-mounted pusher propellor; the C 1 was a failure. First flown in 1927, the experimental Focke-Wulf F 19 "Ente" was more successful. Two examples were built and one of them continued flying until 1931. Before and during World War II several experimental canard fighters were flown, including the Ambrosini SS.4, Curtiss-Wright XP-55 Ascender and Kyūshū J7W1 Shinden. These were attempts at using the canard configuration to give advantages in areas such as performance, armament disposition or pilot view, but no production aircraft were completed.
The Shinden was ordered into production "off the drawing board" but hostilities ceased before any other than prototypes had flown. Just after the end of World War II in Europe in 1945, what may have been the first canard designed and flown in the Soviet Union appeared as a test aircraft, the lightweight Mikoyan-Gurevich MiG-8 Utka, it was a favorite among MiG OKB test pilots for its docile, slow-speed handling characteristics and flew for some years, being used as a testbed during development of the swept wing of the MiG-15 jet fighter. With the arrival of the jet age and supersonic flight, American designers, notably North American Aviation, began to experiment with supersonic canard delta designs, with some such as the North American XB-70 Valkyrie and the Soviet equivalent Sukhoi T-4 flying in prototype form, but the stability and control problems encountered prevented widespread adoption. In 1963 the Swedish company Saab patented a delta-winged design which overcame the earlier problems, in what has become known as the close-coupled canard.
It was built as the Saab 37 Viggen and in 1967 became the first modern canard aircraft to enter production. The success of this aircraft spurred many designers, canard surfaces sprouted on a number of types derived from the popular Dassault Mirage delta-winged jet fighter; these included variants of the French Dassault Mirage III, Israeli IAI Kfir and South African Atlas Cheetah. The close-coupled canard delta remains a popular configuration for combat aircraft; the Viggen inspired the American Burt Rutan to create a two-seater homebuilt canard delta design, accordingly named VariViggen and flown in 1972. Rutan abandoned the delta wing as unsuited to such light aircraft, his next two canard designs, the Long-EZ had longer-span swept wings. These designs were not only successful and built in large numbers but were radically different from anything seen before. Rutan's ideas soon spread to other designers. From the 1980s they found favour in the executive market with the appearance of types such as the OMAC Laser 300, Avtek 400 and Beech Starship.
Static canard designs can have complex interactions in airflow between the canard and the main wing, leading to issues with stability and behaviour in the stall. This limits their applicability; the development of fly-by-wire and artificial stability towards the end of the century opened the way for computerized controls to begin turning these complex effects fro
Thermodynamic temperature
Thermodynamic temperature is the absolute measure of temperature and is one of the principal parameters of thermodynamics. Thermodynamic temperature is defined by the third law of thermodynamics in which the theoretically lowest temperature is the null or zero point. At this point, absolute zero, the particle constituents of matter have minimal motion and can become no colder. In the quantum-mechanical description, matter at absolute zero is in its ground state, its state of lowest energy. Thermodynamic temperature is also called absolute temperature, for two reasons: one, proposed by Kelvin, that it does not depend on the properties of a particular material; the International System of Units specifies a particular scale for thermodynamic temperature. It uses the kelvin scale for measurement and selects the triple point of water at 273.16 K as the fundamental fixing point. Other scales have been in use historically; the Rankine scale, using the degree Fahrenheit as its unit interval, is still in use as part of the English Engineering Units in the United States in some engineering fields.
ITS-90 gives a practical means of estimating the thermodynamic temperature to a high degree of accuracy. The temperature of a body at rest is a measure of the mean of the energy of the translational and rotational motions of matter's particle constituents, such as molecules and subatomic particles; the full variety of these kinetic motions, along with potential energies of particles, occasionally certain other types of particle energy in equilibrium with these, make up the total internal energy of a substance. Internal energy is loosely called the heat energy or thermal energy in conditions when no work is done upon the substance by its surroundings, or by the substance upon the surroundings. Internal energy may be stored in a number of ways within a substance, each way constituting a "degree of freedom". At equilibrium, each degree of freedom will have on average the same energy: k B T / 2 where k B is the Boltzmann constant, unless that degree of freedom is in the quantum regime; the internal degrees of freedom may be in the quantum regime at room temperature, but the translational degrees of freedom will be in the classical regime except at low temperatures and it may be said that, for most situations, the thermodynamic temperature is specified by the average translational kinetic energy of the particles.
Temperature is a measure of the random submicroscopic motions and vibrations of the particle constituents of matter. These motions comprise the internal energy of a substance. More the thermodynamic temperature of any bulk quantity of matter is the measure of the average kinetic energy per classical degree of freedom of its constituent particles. "Translational motions" are always in the classical regime. Translational motions are ordinary, whole-body movements in three-dimensional space in which particles move about and exchange energy in collisions. Figure 1 below shows translational motion in gases. Thermodynamic temperature's null point, absolute zero, is the temperature at which the particle constituents of matter are as close as possible to complete rest. Zero kinetic energy remains in a substance at absolute zero. Throughout the scientific world where measurements are made in SI units, thermodynamic temperature is measured in kelvins. Many engineering fields in the U. S. however, measure thermodynamic temperature using the Rankine scale.
By international agreement, the unit kelvin and its scale are defined by two points: absolute zero, the triple point of Vienna Standard Mean Ocean Water. Absolute zero, the lowest possible temperature, is defined as being 0 K and −273.15 °C. The triple point of water is defined as being 273.16 K and 0.01 °C. This definition does three things: It fixes the magnitude of the kelvin unit as being 1 part in 273.16 parts the difference between absolute zero and the triple point of water. Temperatures expressed in kelvins are converted to degrees Rankine by multiplying by 1.8. Temperatures expressed in degrees Rankine are converted to kelvins by dividing by 1.8. Although the kelvin and Celsius scales are defined using absolute zero and the triple point of water, it is impractical to use this definition at temperatures that are different from the triple point of water. ITS-90 is designed to represent the thermodynamic temperature as as possible throughout its range. Many different thermometer designs are required to cover the entire range.
These include helium vapor pressure thermometers, helium gas thermometers, standard platinum resistance thermometers and monochromatic radiation thermometers. For some types of thermometer the relationship between the property observed and temperature, is close to linear, so for most purposes a linear scale is sufficient, without point-by-point calibration
Turbofan
The turbofan or fanjet is a type of airbreathing jet engine, used in aircraft propulsion. The word "turbofan" is a portmanteau of "turbine" and "fan": the turbo portion refers to a gas turbine engine which achieves mechanical energy from combustion, the fan, a ducted fan that uses the mechanical energy from the gas turbine to accelerate air rearwards. Thus, whereas all the air taken in by a turbojet passes through the turbine, in a turbofan some of that air bypasses the turbine. A turbofan thus can be thought of as a turbojet being used to drive a ducted fan, with both of these contributing to the thrust; the ratio of the mass-flow of air bypassing the engine core divided by the mass-flow of air passing through the core is referred to as the bypass ratio. The engine produces thrust through a combination of these two portions working together. Most commercial aviation jet engines in use today are of the high-bypass type, most modern military fighter engines are low-bypass. Afterburners are not used on high-bypass turbofan engines but may be used on either low-bypass turbofan or turbojet engines.
Modern turbofans have either a smaller fan with several stages. An early configuration combined a low-pressure fan in a single rear-mounted unit. Turbofans were invented to circumvent an awkward feature of turbojets, that they were inefficient for subsonic flight. To raise the efficiency of a turbojet, the obvious approach would be to increase the burner temperature, to give better Carnot efficiency and fit larger compressors and nozzles. However, while that does increase thrust somewhat, the exhaust jet leaves the engine with higher velocity, which at subsonic flight speeds, takes most of the extra energy with it, wasting fuel. Instead, a turbofan can be thought of as a turbojet being used to drive a ducted fan, with both of those contributing to the thrust. Whereas all the air taken in by a turbojet passes through the turbine, in a turbofan some of that air bypasses the turbine; because the turbine has to additionally drive the fan, the turbine is larger and has larger pressure and temperature drops, so the nozzles are smaller.
This means. The fan has lower exhaust velocity, giving much more thrust per unit energy; the overall effective exhaust velocity of the two exhaust jets can be made closer to a normal subsonic aircraft's flight speed. In effect, a turbofan emits a large amount of air more whereas a turbojet emits a smaller amount of air, a far less efficient way to generate the same thrust; the ratio of the mass-flow of air bypassing the engine core compared to the mass-flow of air passing through the core is referred to as the bypass ratio. The engine produces thrust through a combination of these two portions working together. Most commercial aviation jet engines in use today are of the high-bypass type, most modern military fighter engines are low-bypass. Afterburners are not used on high-bypass turbofan engines but may be used on either low-bypass turbofan or turbojet engines; the bypass ratio of a turbofan engine is the ratio between the mass flow rate of the bypass stream to the mass flow rate entering the core.
A 10:1 bypass ratio, for example, means that 10 kg of air passes through the bypass duct for every 1 kg of air passing through the core. Turbofan engines are described in terms of BPR, which together with overall pressure ratio, turbine inlet temperature and fan pressure ratio are important design parameters. In addition bpr is quoted for turboprop and unducted fan installations because their high propulsive efficiency gives them the overall efficiency characteristics of high bypass turbofans; this allows them to be shown together with turbofans on plots which show trends of reducing specific fuel consumption with increasing BPS. BPR can be quoted for lift fan installations where the fan airflow is remote from the engine and doesn't physically touch the engine core. Bypass provides a lower fuel consumption for the same thrust. If all the gas power from a gas turbine is converted to kinetic energy in a propelling nozzle, the aircraft is best suited to high supersonic speeds. If it is all transferred to a separate big mass of air with low kinetic energy, the aircraft is best suited to zero speed.
For speeds in between, the gas power is shared between a separate airstream and the gas turbine's own nozzle flow in a proportion which gives the aircraft performance required. The trade off between mass flow and velocity is seen with propellers and helicopter rotors by comparing disc loading and power loading. For example, the same helicopter weight can be supported by a high power engine and small diameter rotor or, for less fuel, a lower power engine and bigger rotor with lower velocity through the rotor. Bypass refers to transferring gas power from a gas turbine to a bypass stream of air to reduce fuel consumption and jet noise. Alternatively, there may be a requirement for an afterburning engine where the sole requirement for bypass is to provide cooling air; this sets the lower limit for bpr and these engines have been called "leaky" or continuous bleed turbojets and low bpr turbojets. Low bpr has bee
Atmosphere of Earth
The atmosphere of Earth is the layer of gases known as air, that surrounds the planet Earth and is retained by Earth's gravity. The atmosphere of Earth protects life on Earth by creating pressure allowing for liquid water to exist on the Earth's surface, absorbing ultraviolet solar radiation, warming the surface through heat retention, reducing temperature extremes between day and night. By volume, dry air contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, small amounts of other gases. Air contains a variable amount of water vapor, on average around 1% at sea level, 0.4% over the entire atmosphere. Air content and atmospheric pressure vary at different layers, air suitable for use in photosynthesis by terrestrial plants and breathing of terrestrial animals is found only in Earth's troposphere and in artificial atmospheres; the atmosphere has a mass of about 5.15×1018 kg, three quarters of, within about 11 km of the surface. The atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space.
The Kármán line, at 100 km, or 1.57% of Earth's radius, is used as the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around 120 km. Several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition; the study of Earth's atmosphere and its processes is called atmospheric science. Early pioneers in the field include Richard Assmann; the three major constituents of Earth's atmosphere are nitrogen and argon. Water vapor accounts for 0.25% of the atmosphere by mass. The concentration of water vapor varies from around 10 ppm by volume in the coldest portions of the atmosphere to as much as 5% by volume in hot, humid air masses, concentrations of other atmospheric gases are quoted in terms of dry air; the remaining gases are referred to as trace gases, among which are the greenhouse gases, principally carbon dioxide, nitrous oxide, ozone. Filtered air includes trace amounts of many other chemical compounds.
Many substances of natural origin may be present in locally and seasonally variable small amounts as aerosols in an unfiltered air sample, including dust of mineral and organic composition and spores, sea spray, volcanic ash. Various industrial pollutants may be present as gases or aerosols, such as chlorine, fluorine compounds and elemental mercury vapor. Sulfur compounds such as hydrogen sulfide and sulfur dioxide may be derived from natural sources or from industrial air pollution; the relative concentration of gases remains constant until about 10,000 m. In general, air pressure and density decrease with altitude in the atmosphere. However, temperature has a more complicated profile with altitude, may remain constant or increase with altitude in some regions; because the general pattern of the temperature/altitude profile is constant and measurable by means of instrumented balloon soundings, the temperature behavior provides a useful metric to distinguish atmospheric layers. In this way, Earth's atmosphere can be divided into five main layers.
Excluding the exosphere, the atmosphere has four primary layers, which are the troposphere, stratosphere and thermosphere. From highest to lowest, the five main layers are: Exosphere: 700 to 10,000 km Thermosphere: 80 to 700 km Mesosphere: 50 to 80 km Stratosphere: 12 to 50 km Troposphere: 0 to 12 km The exosphere is the outermost layer of Earth's atmosphere, it extends from the exobase, located at the top of the thermosphere at an altitude of about 700 km above sea level, to about 10,000 km where it merges into the solar wind. This layer is composed of low densities of hydrogen and several heavier molecules including nitrogen and carbon dioxide closer to the exobase; the atoms and molecules are so far apart that they can travel hundreds of kilometers without colliding with one another. Thus, the exosphere no longer behaves like a gas, the particles escape into space; these free-moving particles follow ballistic trajectories and may migrate in and out of the magnetosphere or the solar wind. The exosphere is located too far above Earth for any meteorological phenomena to be possible.
However, the aurora borealis and aurora australis sometimes occur in the lower part of the exosphere, where they overlap into the thermosphere. The exosphere contains most of the satellites orbiting Earth; the thermosphere is the second-highest layer of Earth's atmosphere. It extends from the mesopause at an altitude of about 80 km up to the thermopause at an altitude range of 500–1000 km; the height of the thermopause varies due to changes in solar activity. Because the thermopause lies at the lower boundary of the exosphere, it is referred to as the exobase; the lower part of the thermosphere, from 80 to 550 kilometres above Earth's surface, contains the ionosphere. The temperature of the thermosphere increases with height. Unlike the stratosphere beneath it, wherein a temperature inversion is due to the absorption of radiation by ozone, the inversion in the t
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![{\displaystyle \mathrm {M} ={\sqrt {{\frac {2}{\gamma -1}}\left[\left({\frac {q_{c}}{p}}+1\right)^{\frac {\gamma -1}{\gamma }}-1\right]}}\,}](https://wikimedia.org/api/rest_v1/media/math/render/svg/b6cfb0b14f5726032a386928f8312725a3325c4c)
![{\displaystyle {\frac {p_{t}}{p}}=\left[{\frac {\gamma +1}{2}}\mathrm {M} ^{2}\right]^{\frac {\gamma }{\gamma -1}}\cdot \left[{\frac {\gamma +1}{1-\gamma +2\gamma \,\mathrm {M} ^{2}}}\right]^{\frac {1}{\gamma -1}}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/e40925c7d73812aaeb7be0541fb045abfe268c54)
![{\displaystyle \mathrm {M} ={\sqrt {5\left[\left({\frac {q_{c}}{p}}+1\right)^{\frac {2}{7}}-1\right]}}\,}](https://wikimedia.org/api/rest_v1/media/math/render/svg/dbbe331c3f8c63b187b0a3a3fc23580e4cb2ac55)
