86-634: The FMRAAM (Future Medium Range Air to Air Missile) was a modified ramjet powered version of the Hughes (now Raytheon ) AIM-120 AMRAAM beyond visual range air-to-air missile that was conceived during the mid-1990s to fulfill British requirements for a new longer range missile to use in place of the AMRAAM on their new Eurofighter Typhoon fighter. It competed with and lost to the MBDA Meteor , thus never reaching production. This aviation -related article
172-444: A l = γ ⋅ p ρ = γ ⋅ R ⋅ T M = γ ⋅ k ⋅ T m , {\displaystyle c_{\mathrm {ideal} }={\sqrt {\gamma \cdot {p \over \rho }}}={\sqrt {\gamma \cdot R\cdot T \over M}}={\sqrt {\gamma \cdot k\cdot T \over m}},} where This equation applies only when
258-400: A convergent–divergent nozzle . Although ramjets have been run as slow as 45 metres per second (160 km/h; 100 mph), below about Mach 0.5 (170 m/s; 610 km/h; 380 mph) they give little thrust and are highly inefficient due to their low pressure ratios. Above this speed, given sufficient initial flight velocity, a ramjet is self-sustaining. Unless the vehicle drag
344-402: A dispersive medium , the speed of sound is a function of sound frequency, through the dispersion relation . Each frequency component propagates at its own speed, called the phase velocity , while the energy of the disturbance propagates at the group velocity . The same phenomenon occurs with light waves; see optical dispersion for a description. The speed of sound is variable and depends on
430-729: A long-range antipodal bomber , similar to the Sänger-Bredt bomber , but powered by ramjet instead of rocket. In 1954, NPO Lavochkin and the Keldysh Institute began development of a Mach 3 ramjet-powered cruise missile, Burya . This project competed with the R-7 ICBM developed by Sergei Korolev , but was cancelled in 1957. Several ram jets were designed, built, and ground-tested at the Kawasaki Aircraft Company's facility in Gifu during
516-434: A pitot -type opening for the inlet. This is followed by a widening internal passage (subsonic diffuser) to achieve a lower subsonic velocity that is required at the combustor. At low supersonic speeds a normal (planar) shock wave forms in front of the inlet. For higher supersonic speeds the pressure loss through the shock wave becomes prohibitive and a protruding spike or cone is used to produce oblique shock waves in front of
602-409: A turbine , which generates its own compressed air (i.e. ram air in a ramjet) in order to generate thrust. The diffuser converts the high velocity of the air approaching the intake into high (static) pressure required for combustion. High combustion pressures minimise entropy rise during heat addition, this minimising wasted thermal energy in the exhaust gases Subsonic and low-supersonic ramjets use
688-510: A combustor exit stagnation temperature of the order of 2,400 K (2,130 °C; 3,860 °F) for kerosene . Normally, the combustor must be capable of operating over a wide range of throttle settings, matching flight speeds and altitudes. Usually, a sheltered pilot region enables combustion to continue when the vehicle intake undergoes high yaw/pitch during turns. Other flame stabilization techniques make use of flame holders, which vary in design from combustor cans to flat plates, to shelter
774-429: A compact mechanism for high-speed, such as missiles . Weapons designers are investigating ramjet technology for use in artillery shells to increase range; a 120 mm ramjet-assisted mortar shell is thought to be able to travel 35 km (22 mi). They have been used, though not efficiently, as tip jets on the ends of helicopter rotors. L'Autre Monde: ou les États et Empires de la Lune ( Comical History of
860-453: A compression wave in a fluid is determined by the medium's compressibility and density . In solids, the compression waves are analogous to those in fluids, depending on compressibility and density, but with the additional factor of shear modulus which affects compression waves due to off-axis elastic energies which are able to influence effective tension and relaxation in a compression. The speed of shear waves, which can occur only in solids,
946-410: A computation of the speed of sound in air as 979 feet per second (298 m/s). This is too low by about 15%. The discrepancy is due primarily to neglecting the (then unknown) effect of rapidly fluctuating temperature in a sound wave (in modern terms, sound wave compression and expansion of air is an adiabatic process , not an isothermal process ). This error was later rectified by Laplace . During
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#17328443112381032-414: A final normal shock that occurs at the inlet entrance lip. The diffuser in this case consists of two parts, the supersonic diffuser, with shock waves external to the inlet, followed by the internal subsonic diffuser. At higher speeds still, part of the supersonic diffusion has to take place internally, requiring external and internal oblique shock waves. The final normal shock has to occur in the vicinity of
1118-462: A hot fuel-rich gas which is burnt in the ramcombustor with the compressed air supplied by the intake(s). The flow of gas improves the mixing of the fuel and air and increases total pressure recovery. In a throttleable ducted rocket, also known as a variable flow ducted rocket, a valve allows the gas generator exhaust to be throttled allowing thrust control. Unlike an LFRJ, solid propellant ramjets cannot flame out . The ducted rocket sits somewhere between
1204-462: A minimum flow area known as the throat, which is followed by the subsonic diffuser. As with other jet engines, the combustor raises the air temperature by burning fuel. This takes place with a small pressure loss. The air velocity entering the combustor has to be low enough such that continuous combustion can take place in sheltered zones provided by flame holders . A ramjet combustor can safely operate at stoichiometric fuel:air ratios. This implies
1290-517: A modified Polikarpov I-15 . Merkulov designed a ramjet fighter "Samolet D" in 1941, which was never completed. Two of his DM-4 engines were installed on the Yak-7 PVRD fighter during World War II. In 1940, the Kostikov-302 experimental plane was designed, powered by a liquid fuel rocket for take-off and ramjet engines for flight. That project was cancelled in 1944. In 1947, Mstislav Keldysh proposed
1376-410: A nozzle to accelerate it to supersonic speeds and generate forward thrust . Ramjets are much less complex than turbojets or turbofans , requiring only an air intake, a combustor, and a nozzle to be built. Additionally, ramjets have little to no moving parts - liquid-fuel ramjets have only a fuel pump, whilst solid-fuel ramjets lack even this. By comparison, a turbojet uses a compressor driven by
1462-486: A pipe aligned with the x {\displaystyle x} axis and with a cross-sectional area of A {\displaystyle A} . In time interval d t {\displaystyle dt} it moves length d x = v d t {\displaystyle dx=v\,dt} . In steady state , the mass flow rate m ˙ = ρ v A {\displaystyle {\dot {m}}=\rho vA} must be
1548-558: A range of about 105 kilometres (65 miles). It was also used as a surface-to-surface weapon and was modified to destroy land-based radars. Using technology proven by the AQM-60, In the late 1950s and early 1960s the US produced a widespread defense system called the CIM-10 Bomarc , which was equipped with hundreds of nuclear armed ramjet missiles with a range of several hundred miles. It was powered by
1634-456: A single given gas (assuming the molecular weight does not change) and over a small temperature range (for which the heat capacity is relatively constant), the speed of sound becomes dependent on only the temperature of the gas. In non-ideal gas behavior regimen, for which the Van der Waals gas equation would be used, the proportionality is not exact, and there is a slight dependence of sound velocity on
1720-518: A solid fuel ramjet (SFRJ) vehicle test in August 2022. In 2023, General Electric demonstrated a ramjet with rotating detonation combustion. It is a turbine-based combined-cycle engine that incorporates a In the late 1950s, 1960s, and early 1970s, the UK developed several ramjet missiles. The Blue Envoy project was supposed to equip the country with a long range ramjet powered air defense against bombers, but
1806-588: A special test rig on a Dornier Do 17 Z at flight speeds of up to 200 metres per second (720 km/h). Later, as petrol became scarce in Germany, tests were carried out with blocks of pressed coal dust as a fuel (see e.g. Lippisch P.13a ), which were not successful due to slow combustion. Stovepipe (flying/flaming/supersonic) was a popular name for the ramjet during the 1950s in trade magazines such as Aviation Week & Space Technology and other publications such as The Cornell Engineer. The simplicity implied by
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#17328443112381892-481: A speed of Mach 3. It was used successfully in combat against multiple types of aircraft during the Falklands War . Eminent Swiss astrophysicist Fritz Zwicky was research director at Aerojet and holds many patents in jet propulsion. Patents US 5121670 and US 4722261 are for ram accelerators . The U.S. Navy would not allow Zwicky to publicly discuss his invention, US 2461797
1978-439: A tandem arrangement. Integrated boosters provide a more efficient packaging option, since the booster propellant is cast inside the otherwise empty combustor. This approach has been used on solid-fuel ramjets (SFRJ), for example 2K12 Kub , liquid, for example ASMP , and ducted rocket, for example Meteor , designs. Integrated designs are complicated by the different nozzle requirements of the boost and ramjet flight phases. Due to
2064-433: Is a stub . You can help Misplaced Pages by expanding it . Ramjet A ramjet is a form of airbreathing jet engine that requires forward motion of the engine to provide air for combustion. Ramjets work most efficiently at supersonic speeds around Mach 3 (2,300 mph; 3,700 km/h) and can operate up to Mach 6 (4,600 mph; 7,400 km/h). Ramjets can be particularly appropriate in uses requiring
2150-419: Is associated with compression and decompression in the direction of travel, and is the same process in gases and liquids, with an analogous compression-type wave in solids. Only compression waves are supported in gases and liquids. An additional type of wave, the transverse wave , also called a shear wave , occurs only in solids because only solids support elastic deformations. It is due to elastic deformation of
2236-417: Is called the object's Mach number . Objects moving at speeds greater than the speed of sound ( Mach 1 ) are said to be traveling at supersonic speeds . In Earth's atmosphere, the speed of sound varies greatly from about 295 m/s (1,060 km/h; 660 mph) at high altitudes to about 355 m/s (1,280 km/h; 790 mph) at high temperatures. Sir Isaac Newton 's 1687 Principia includes
2322-412: Is determined by the medium's compressibility , shear modulus , and density. The speed of shear waves is determined only by the solid material's shear modulus and density. In fluid dynamics , the speed of sound in a fluid medium (gas or liquid) is used as a relative measure for the speed of an object moving through the medium. The ratio of the speed of an object to the speed of sound (in the same medium)
2408-807: Is determined simply by the solid material's shear modulus and density. The speed of sound in mathematical notation is conventionally represented by c , from the Latin celeritas meaning "swiftness". For fluids in general, the speed of sound c is given by the Newton–Laplace equation: c = K s ρ , {\displaystyle c={\sqrt {\frac {K_{s}}{\rho }}},} where K s = ρ ( ∂ P ∂ ρ ) s {\displaystyle K_{s}=\rho \left({\frac {\partial P}{\partial \rho }}\right)_{s}} , where P {\displaystyle P}
2494-543: Is extremely high, the engine/airframe combination tends to accelerate to higher and higher flight speeds, substantially increasing the air intake temperature. As this could damage the engine and/or airframe integrity, the fuel control system must reduce fuel flow to stabilize speed and, thereby, air intake temperature. Due to the stoichiometric combustion temperature, efficiency is usually good at high speeds (around Mach 2 – Mach 3, 680–1,000 m/s, 2,500–3,700 km/h, 1,500–2,300 mph), whereas at low speeds
2580-545: Is for the Underwater Jet, a ram jet that performs in a fluid medium. Time magazine reported on Zwicky's work. The first part of a ramjet is its diffuser (compressor) in which the forward motion of the ramjet is used to raise the pressure of its working fluid (air) as required for combustion. Air is compressed, heated by combustion and expanded in a thermodynamic cycle known as the Brayton cycle , before being passed through
2666-577: Is fully excited (i.e., molecular rotation is fully used as a heat energy "partition" or reservoir); but at the same time the temperature must be low enough that molecular vibrational modes contribute no heat capacity (i.e., insignificant heat goes into vibration, as all vibrational quantum modes above the minimum-energy-mode have energies that are too high to be populated by a significant number of molecules at this temperature). For air, these conditions are fulfilled at room temperature, and also temperatures considerably below room temperature (see tables below). See
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2752-430: Is the distance travelled per unit of time by a sound wave as it propagates through an elastic medium. More simply, the speed of sound is how fast vibrations travel. At 20 °C (68 °F), the speed of sound in air is about 343 m/s (1,125 ft/s ; 1,235 km/h ; 767 mph ; 667 kn ), or 1 km in 2.91 s or one mile in 4.69 s . It depends strongly on temperature as well as
2838-472: Is the pressure and the derivative is taken isentropically, that is, at constant entropy s . This is because a sound wave travels so fast that its propagation can be approximated as an adiabatic process , meaning that there isn't enough time, during a pressure cycle of the sound, for significant heat conduction and radiation to occur. Thus, the speed of sound increases with the stiffness (the resistance of an elastic body to deformation by an applied force) of
2924-412: Is through ablation of the propellant by the hot compressed air from the intake(s). An aft mixer may be used to improve combustion efficiency . SFIRRs are preferred over LFRJs for some applications because of the simplicity of the fuel supply, but only when the throttling requirements are minimal, i.e. when variations in altitude or speed are limited. In a ducted rocket, a solid fuel gas generator produces
3010-476: The Austro-Hungarian Army , but the proposal was rejected. After World War I, Fonó returned to the subject. In May 1928 he described an "air-jet engine" which he described as suitable for high-altitude supersonic aircraft, in a German patent application. In an additional patent application, he adapted the engine for subsonic speed. The patent was granted in 1932 (German Patent No. 554,906, 1932-11-02). In
3096-558: The Leduc 0.10 was one of the first ramjet-powered aircraft to fly, in 1949. The Nord 1500 Griffon reached Mach 2.19 (745 m/s; 2,680 km/h) in 1958. In 1915, Hungarian inventor Albert Fonó devised a solution for increasing the range of artillery , comprising a gun-launched projectile united with a ramjet propulsion unit, thus giving a long range from relatively low muzzle velocities, allowing heavy shells to be fired from relatively lightweight guns. Fonó submitted his invention to
3182-616: The Lockheed D-21 spy drone. In the late 1950s the US Navy introduced a system called the RIM-8 Talos , which was a long range surface-to-air missile fired from ships. It successfully shot down enemy fighters during the Vietnam War , and was the first ship-launched missile to destroy an enemy aircraft in combat. On 23 May 1968, a Talos fired from USS Long Beach shot down a Vietnamese MiG at
3268-446: The ozone layer . This produces a positive speed of sound gradient in this region. Still another region of positive gradient occurs at very high altitudes, in the thermosphere above 90 km . For an ideal gas, K (the bulk modulus in equations above, equivalent to C , the coefficient of stiffness in solids) is given by K = γ ⋅ p . {\displaystyle K=\gamma \cdot p.} Thus, from
3354-548: The springs , and the mass of the spheres. As long as the spacing of the spheres remains constant, stiffer springs/bonds transmit energy more quickly, while more massive spheres transmit energy more slowly. In a real material, the stiffness of the springs is known as the " elastic modulus ", and the mass corresponds to the material density . Sound will travel more slowly in spongy materials and faster in stiffer ones. Effects like dispersion and reflection can also be understood using this model. Some textbooks mistakenly state that
3440-605: The "One o'Clock Gun" is fired at the eastern end of Edinburgh Castle. Standing at the base of the western end of the Castle Rock, the sound of the Gun can be heard through the rock, slightly before it arrives by the air route, partly delayed by the slightly longer route. It is particularly effective if a multi-gun salute such as for "The Queen's Birthday" is being fired. In a gas or liquid, sound consists of compression waves. In solids, waves propagate as two different types. A longitudinal wave
3526-575: The 17th century there were several attempts to measure the speed of sound accurately, including attempts by Marin Mersenne in 1630 (1,380 Parisian feet per second), Pierre Gassendi in 1635 (1,473 Parisian feet per second) and Robert Boyle (1,125 Parisian feet per second). In 1709, the Reverend William Derham , Rector of Upminster, published a more accurate measure of the speed of sound, at 1,072 Parisian feet per second. (The Parisian foot
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3612-405: The Newton–Laplace equation above, the speed of sound in an ideal gas is given by c = γ ⋅ p ρ , {\displaystyle c={\sqrt {\gamma \cdot {p \over \rho }}},} where Using the ideal gas law to replace p with nRT / V , and replacing ρ with nM / V , the equation for an ideal gas becomes c i d e
3698-577: The Second World War. Company officials claimed, in December 1945, that these domestic initiatives were uninfluenced by parallel German developments. One post-war U.S. intelligence assessment described the Kawasaki ram jet's centrifugal fuel disperser as the company's "most outstanding accomplishment ... eliminat[ing] a large amount of the fuel injection system normally employed." Because of excessive vibration,
3784-552: The Soviet Union, a theory of supersonic ramjet engines was presented in 1928 by Boris Stechkin . Yuri Pobedonostsev, chief of GIRD 's 3rd Brigade, carried out research. The first engine, the GIRD-04, was designed by I.A. Merkulov and tested in April 1933. To simulate supersonic flight, it was fed by air compressed to 200 bar , and was fueled with hydrogen. The GIRD-08 phosphorus-fueled ramjet
3870-566: The States and Empires of the Moon ) (1657) was the first of three satirical novels written by Cyrano de Bergerac that are considered among the first science fiction stories. Arthur C Clarke credited this book with conceiving the ramjet, and as the first fictional example of rocket-powered space flight. The ramjet was designed in 1913 by French inventor René Lorin , who was granted a patent (FR290356) for his device. He could not test his invention due to
3956-421: The booster is mounted immediately aft of the ramjet, e.g. Sea Dart , or wraparound where multiple boosters are attached around the outside of the ramjet, e.g. 2K11 Krug . The choice of booster arrangement is usually driven by the size of the launch platform. A tandem booster increases the length of the system, whereas wraparound boosters increase the diameter. Wraparound boosters typically generate higher drag than
4042-496: The booster's higher thrust levels, a differently shaped nozzle is required for optimum thrust compared to that required for the lower thrust ramjet sustainer. This is usually achieved via a separate nozzle, which is ejected after booster burnout. However, designs such as Meteor feature nozzleless boosters. This offers the advantages of elimination of the hazard to launch aircraft from the boost debris, simplicity, reliability, and reduced mass and cost, although this must be traded against
4128-457: The compressed air bottle from which it is inflated, which is mounted lengthwise in the tank. This offers a lower-cost approach than a regulated LFRJ requiring a pump system to supply the fuel. A ramjet generates no static thrust and needs a booster to achieve a forward velocity high enough for efficient operation of the intake system. The first ramjet-powered missiles used external boosters, usually solid-propellant rockets, either in tandem, where
4214-456: The denser materials. An illustrative example of the two effects is that sound travels only 4.3 times faster in water than air, despite enormous differences in compressibility of the two media. The reason is that the greater density of water, which works to slow sound in water relative to the air, nearly makes up for the compressibility differences in the two media. For instance, sound will travel 1.59 times faster in nickel than in bronze, due to
4300-630: The engine was only intended for use in rocket, or catapult-launched pilotless aircraft. Preparations for flight testing ended with the Japanese surrender in August 1945. In 1936, Hellmuth Walter constructed a test engine powered by natural gas . Theoretical work was carried out at BMW , Junkers , and DFL . In 1941, Eugen Sänger of DFL proposed a ramjet engine with a high combustion chamber temperature. He constructed large ramjet pipes with 500 millimetres (20 in) and 1,000 millimetres (39 in) diameter and carried out combustion tests on lorries and on
4386-445: The fastest it can travel under normal conditions. In theory, the speed of sound is actually the speed of vibrations. Sound waves in solids are composed of compression waves (just as in gases and liquids) and a different type of sound wave called a shear wave , which occurs only in solids. Shear waves in solids usually travel at different speeds than compression waves, as exhibited in seismology . The speed of compression waves in solids
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#17328443112384472-427: The flame and improve fuel mixing. Over-fuelling the combustor can cause the final (normal) shock in the diffuser to be pushed forward beyond the intake lip, resulting in a substantial drop in airflow and thrust. The propelling nozzle is a critical part of a ramjet design, since it accelerates exhaust flow to produce thrust. Subsonic ramjets accelerate exhaust flow with a nozzle . Supersonic flight typically requires
4558-418: The fuel to the ramcombustor is required, which can be complicated and expensive. This propulsion system was first perfected by Yvonne Brill during her work at Marquardt Corporation . Aérospatiale-Celerg designed an LFRJ where the fuel is forced into the injectors by an elastomer bladder that inflates progressively along the length of the fuel tank. Initially, the bladder forms a close-fitting sheath around
4644-473: The gas pressure. Humidity has a small but measurable effect on the speed of sound (causing it to increase by about 0.1%–0.6%), because oxygen and nitrogen molecules of the air are replaced by lighter molecules of water . This is a simple mixing effect. In the Earth's atmosphere , the chief factor affecting the speed of sound is the temperature . For a given ideal gas with constant heat capacity and composition,
4730-610: The greater stiffness of nickel at about the same density. Similarly, sound travels about 1.41 times faster in light hydrogen ( protium ) gas than in heavy hydrogen ( deuterium ) gas, since deuterium has similar properties but twice the density. At the same time, "compression-type" sound will travel faster in solids than in liquids, and faster in liquids than in gases, because the solids are more difficult to compress than liquids, while liquids, in turn, are more difficult to compress than gases. A practical example can be observed in Edinburgh when
4816-401: The ground, creating an acoustic shadow at some distance from the source. The decrease of the speed of sound with height is referred to as a negative sound speed gradient . However, there are variations in this trend above 11 km . In particular, in the stratosphere above about 20 km , the speed of sound increases with height, due to an increase in temperature from heating within
4902-413: The gunshot with a half-second pendulum. Measurements were made of gunshots from a number of local landmarks, including North Ockendon church. The distance was known by triangulation , and thus the speed that the sound had travelled was calculated. The transmission of sound can be illustrated by using a model consisting of an array of spherical objects interconnected by springs. In real material terms,
4988-466: The important factors, since fluids do not transmit shear stresses. In heterogeneous fluids, such as a liquid filled with gas bubbles, the density of the liquid and the compressibility of the gas affect the speed of sound in an additive manner, as demonstrated in the hot chocolate effect . In gases, adiabatic compressibility is directly related to pressure through the heat capacity ratio (adiabatic index), while pressure and density are inversely related to
5074-425: The incoming air is slowed to subsonic velocities for combustion. In addition, the combustion chamber's inlet temperature increases to very high values, approaching the dissociation limit at some limiting Mach number. Ramjet diffusers slow the incoming air to a subsonic velocity before it enters the combustor. Scramjets are similar to ramjets, but the air flows through the combustor at supersonic speed. This increases
5160-473: The material and decreases with an increase in density. For ideal gases, the bulk modulus K is simply the gas pressure multiplied by the dimensionless adiabatic index , which is about 1.4 for air under normal conditions of pressure and temperature. For general equations of state , if classical mechanics is used, the speed of sound c can be derived as follows: Consider the sound wave propagating at speed v {\displaystyle v} through
5246-563: The medium perpendicular to the direction of wave travel; the direction of shear-deformation is called the " polarization " of this type of wave. In general, transverse waves occur as a pair of orthogonal polarizations. These different waves (compression waves and the different polarizations of shear waves) may have different speeds at the same frequency. Therefore, they arrive at an observer at different times, an extreme example being an earthquake , where sharp compression waves arrive first and rocking transverse waves seconds later. The speed of
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#17328443112385332-451: The medium through which a sound wave is propagating. At 0 °C (32 °F), the speed of sound in air is about 331 m/s (1,086 ft/s; 1,192 km/h; 740 mph; 643 kn). The speed of sound in an ideal gas depends only on its temperature and composition. The speed has a weak dependence on frequency and pressure in ordinary air, deviating slightly from ideal behavior. In colloquial speech, speed of sound refers to
5418-474: The name came from a comparison with the turbojet engine which employs relatively complex and expensive spinning turbomachinery. The US Navy developed a series of air-to-air missiles under the name of " Gorgon " using different propulsion mechanisms, including ramjet propulsion on the Gorgon IV. The ramjet Gorgon IVs, made by Glenn Martin , were tested in 1948 and 1949 at Naval Air Station Point Mugu . The ramjet
5504-525: The pressure recovered from the streaming air and improves net thrust. Thermal choking of the exhaust is avoided by having a relatively high supersonic air velocity at combustor entry. Fuel injection is often into a sheltered region below a step in the combustor wall. The Boeing X-43 was a small experimental ramjet that achieved Mach 5 (1,700 m/s; 6,100 km/h) for 200 seconds on the X-51A Waverider . Speed of sound The speed of sound
5590-432: The properties of the substance through which the wave is travelling. In solids, the speed of transverse (or shear) waves depends on the shear deformation under shear stress (called the shear modulus ), and the density of the medium. Longitudinal (or compression) waves in solids depend on the same two factors with the addition of a dependence on compressibility . In fluids, only the medium's compressibility and density are
5676-437: The reduction in performance of a dedicated booster nozzle. A slight variation on the ramjet uses the supersonic exhaust from a rocket combustion process to compress and react with the incoming air in the main combustion chamber. This has the advantage of giving thrust even at zero speed. In a solid fuel integrated rocket ramjet (SFIRR), the solid fuel is cast along the outer wall of the ramcombustor. In this case, fuel injection
5762-430: The relatively low pressure means the ramjets are outperformed by turbojets and rockets . Ramjets can be classified according to the type of fuel, either liquid or solid; and the booster. In a liquid fuel ramjet (LFRJ), hydrocarbon fuel (typically) is injected into the combustor ahead of a flameholder. The flameholder stabilises the flame with the compressed air from the intake(s). A means of pressurizing and supplying
5848-1421: The same at the two ends of the tube, therefore the mass flux j = ρ v {\displaystyle j=\rho v} is constant and v d ρ = − ρ d v {\displaystyle v\,d\rho =-\rho \,dv} . Per Newton's second law , the pressure-gradient force provides the acceleration: d v d t = − 1 ρ d P d x → d P = ( − ρ d v ) d x d t = ( v d ρ ) v → v 2 ≡ c 2 = d P d ρ {\displaystyle {\begin{aligned}{\frac {dv}{dt}}&=-{\frac {1}{\rho }}{\frac {dP}{dx}}\\[1ex]\rightarrow dP&=(-\rho \,dv){\frac {dx}{dt}}=(v\,d\rho )v\\[1ex]\rightarrow v^{2}&\equiv c^{2}={\frac {dP}{d\rho }}\end{aligned}}} And therefore: c = ( ∂ P ∂ ρ ) s = K s ρ , {\displaystyle c={\sqrt {\left({\frac {\partial P}{\partial \rho }}\right)_{s}}}={\sqrt {\frac {K_{s}}{\rho }}},} If relativistic effects are important,
5934-531: The same engines as the AQM-60, but with improved materials to endure longer flight times. The system was withdrawn in the 1970s as the threat from bombers subsided. In April 2020, the U.S. Department of Defense and the Norwegian Ministry of Defense jointly announced their partnership to develop advanced technologies applicable to long range high-speed and hypersonic weapons. The Tactical High-speed Offensive Ramjet for Extended Range (THOR-ER) program completed
6020-461: The section on gases in specific heat capacity for a more complete discussion of this phenomenon. For air, we introduce the shorthand R ∗ = R / M a i r . {\displaystyle R_{*}=R/M_{\mathrm {air} }.} In addition, we switch to the Celsius temperature θ = T − 273.15 K , which is useful to calculate air speed in
6106-1077: The simplicity of the SFRJ and LFRJ's unlimited speed control. Ramjets generally give little or no thrust below about half the speed of sound , and they are inefficient ( specific impulse of less than 600 seconds) until the airspeed exceeds 1,000 kilometres per hour (280 m/s; 620 mph) due to low compression ratios. Even above the minimum speed, a wide flight envelope (range of flight conditions), such as low to high speeds and low to high altitudes, can force significant design compromises, and they tend to work best optimised for one designed speed and altitude (point designs). However, ramjets generally outperform gas turbine-based jet engine designs and work best at supersonic speeds (Mach 2–4). Although inefficient at slower speeds, they are more fuel-efficient than rockets over their entire useful working range up to at least Mach 6 (2,000 m/s; 7,400 km/h). The performance of conventional ramjets falls off above Mach 6 due to dissociation and pressure loss caused by shock as
6192-426: The sound wave is a small perturbation on the ambient condition, and the certain other noted conditions are fulfilled, as noted below. Calculated values for c air have been found to vary slightly from experimentally determined values. Newton famously considered the speed of sound before most of the development of thermodynamics and so incorrectly used isothermal calculations instead of adiabatic . His result
6278-404: The speed of sound increases with density. This notion is illustrated by presenting data for three materials, such as air, water, and steel and noting that the speed of sound is higher in the denser materials. But the example fails to take into account that the materials have vastly different compressibility, which more than makes up for the differences in density, which would slow wave speeds in
6364-423: The speed of sound is about 75% of the mean speed that the atoms move in that gas. For a given ideal gas the molecular composition is fixed, and thus the speed of sound depends only on its temperature . At a constant temperature, the gas pressure has no effect on the speed of sound, since the density will increase, and since pressure and density (also proportional to pressure) have equal but opposite effects on
6450-506: The speed of sound is calculated from the relativistic Euler equations . In a non-dispersive medium , the speed of sound is independent of sound frequency , so the speeds of energy transport and sound propagation are the same for all frequencies. Air, a mixture of oxygen and nitrogen, constitutes a non-dispersive medium. However, air does contain a small amount of CO 2 which is a dispersive medium, and causes dispersion to air at ultrasonic frequencies (greater than 28 kHz ). In
6536-404: The speed of sound is dependent solely upon temperature; see § Details below. In such an ideal case, the effects of decreased density and decreased pressure of altitude cancel each other out, save for the residual effect of temperature. Since temperature (and thus the speed of sound) decreases with increasing altitude up to 11 km , sound is refracted upward, away from listeners on
6622-539: The speed of sound waves in air . However, the speed of sound varies from substance to substance: typically, sound travels most slowly in gases , faster in liquids , and fastest in solids . For example, while sound travels at 343 m/s in air, it travels at 1481 m/s in water (almost 4.3 times as fast) and at 5120 m/s in iron (almost 15 times as fast). In an exceptionally stiff material such as diamond, sound travels at 12,000 m/s (39,370 ft/s), – about 35 times its speed in air and about
6708-490: The speed of sound, and the two contributions cancel out exactly. In a similar way, compression waves in solids depend both on compressibility and density—just as in liquids—but in gases the density contributes to the compressibility in such a way that some part of each attribute factors out, leaving only a dependence on temperature, molecular weight, and heat capacity ratio which can be independently derived from temperature and molecular composition (see derivations below). Thus, for
6794-402: The spheres represent the material's molecules and the springs represent the bonds between them. Sound passes through the system by compressing and expanding the springs, transmitting the acoustic energy to neighboring spheres. This helps transmit the energy in-turn to the neighboring sphere's springs (bonds), and so on. The speed of sound through the model depends on the stiffness /rigidity of
6880-596: The system was cancelled. It was replaced by a shorter range ramjet missile system called the Bloodhound . The system was designed as a second line of defense in case attackers were able to bypass the fleet of defending English Electric Lightning fighters. In the 1960s the Royal Navy developed and deployed a ramjet powered surface to air missile for ships called the Sea Dart . It had a range of 65–130 kilometres (40–80 mi) and
6966-429: The temperature and molecular weight, thus making only the completely independent properties of temperature and molecular structure important (heat capacity ratio may be determined by temperature and molecular structure, but simple molecular weight is not sufficient to determine it). Sound propagates faster in low molecular weight gases such as helium than it does in heavier gases such as xenon . For monatomic gases,
7052-428: The unavailability of adequate equipment since there was no way at the time for an aircraft to go fast enough for a ramjet to function properly. His patent showed a piston internal combustion engine with added 'trumpets' as exhaust nozzles, expressing the idea that the exhaust from internal combustion engines could be directed into nozzles to create jet propulsion. The works of René Leduc were notable. Leduc's Model,
7138-422: Was 325 mm . This is longer than the standard "international foot" in common use today, which was officially defined in 1959 as 304.8 mm , making the speed of sound at 20 °C (68 °F) 1,055 Parisian feet per second). Derham used a telescope from the tower of the church of St. Laurence, Upminster to observe the flash of a distant shotgun being fired, and then measured the time until he heard
7224-655: Was designed at the University of Southern California and manufactured by the Marquardt Aircraft Company . The engine was 2.1 metres (7 ft) long and 510 millimetres (20 in) in diameter and was positioned below the missile. In the early 1950s the US developed a Mach 4+ ramjet under the Lockheed X-7 program. This was developed into the Lockheed AQM-60 Kingfisher . Further development resulted in
7310-435: Was missing the factor of γ but was otherwise correct. Numerical substitution of the above values gives the ideal gas approximation of sound velocity for gases, which is accurate at relatively low gas pressures and densities (for air, this includes standard Earth sea-level conditions). Also, for diatomic gases the use of γ = 1.4000 requires that the gas exists in a temperature range high enough that rotational heat capacity
7396-513: Was tested by firing it from an artillery cannon. These shells may have been the first jet-powered projectiles to break the speed of sound . In 1939, Merkulov did further ramjet tests using a two-stage rocket , the R-3. He developed the first ramjet engine for use as an auxiliary motor of an aircraft, the DM-1. The world's first ramjet-powered airplane flight took place in December 1940, using two DM-2 engines on
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