Sound Barrier
   HOME

TheInfoList



OR:

The sound barrier or sonic barrier is the large increase in
aerodynamic drag In fluid dynamics, drag (sometimes called air resistance, a type of friction, or fluid resistance, another type of friction or fluid friction) is a force acting opposite to the relative motion of any object moving with respect to a surrounding fl ...
and other undesirable effects experienced by an
aircraft An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines ...
or other object when it approaches the
speed of sound The speed of sound is the distance travelled per unit of time by a sound wave as it propagates through an elastic medium. At , the speed of sound in air is about , or one kilometre in or one mile in . It depends strongly on temperature as w ...
. When aircraft first approached the speed of sound, these effects were seen as constituting a barrier, making faster speeds very difficult or impossible. The term ''sound barrier'' is still sometimes used today to refer to aircraft approaching supersonic flight in this high drag regime. Flying faster than sound produces a
sonic boom A sonic boom is a sound associated with shock waves created when an object travels through the air faster than the speed of sound. Sonic booms generate enormous amounts of sound energy, sounding similar to an explosion or a thunderclap to t ...
. In dry air at 20 °C (68 °F), the speed of sound is 343 metres per second (about 767 mph, 1234 km/h or 1,125 ft/s). The term came into use during
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
when pilots of high-speed
fighter aircraft Fighter aircraft are fixed-wing military aircraft designed primarily for air-to-air combat. In military conflict, the role of fighter aircraft is to establish air superiority of the battlespace. Domination of the airspace above a battlefield ...
experienced the effects of
compressibility In thermodynamics and fluid mechanics, the compressibility (also known as the coefficient of compressibility or, if the temperature is held constant, the isothermal compressibility) is a measure of the instantaneous relative volume change of a fl ...
, a number of adverse aerodynamic effects that deterred further acceleration, seemingly impeding flight at speeds close to the speed of sound. These difficulties represented a barrier to flying at faster speeds. In 1947, American test pilot
Chuck Yeager Brigadier General Charles Elwood Yeager ( , February 13, 1923December 7, 2020) was a United States Air Force officer, flying ace, and record-setting test pilot who in October 1947 became the first pilot in history confirmed to have exceeded the ...
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 routinely reached the speed of sound, and faster.


History

Some common whips such as the
bullwhip A bullwhip is a single-tailed whip, usually made of braided leather or nylon, designed as a tool for working with livestock or competition. Bullwhips are pastoral tools, traditionally used to control livestock in open country. A bullwhip's leng ...
or
stockwhip A stockwhip is a type of whip made of a long, tapered length of flexible, plaited leather or nylon with a stiff handle and thong able to pivot along the handle easily. Stock whips are used when mustering cattle.'' Origin and uses The Austral ...
are able to move faster than sound: the tip of the whip exceeds this speed and causes a sharp crack—literally a
sonic boom A sonic boom is a sound associated with shock waves created when an object travels through the air faster than the speed of sound. Sonic booms generate enormous amounts of sound energy, sounding similar to an explosion or a thunderclap to t ...
.
Firearm A firearm is any type of gun designed to be readily carried and used by an individual. The term is legally defined further in different countries (see Legal definitions). The first firearms originated in 10th-century China, when bamboo tubes ...
s made after the 19th century generally have a supersonic
muzzle velocity Muzzle velocity is the speed of a projectile (bullet, pellet, slug, ball/shots or shell) with respect to the muzzle at the moment it leaves the end of a gun's barrel (i.e. the muzzle). Firearm muzzle velocities range from approximately to i ...
. The sound barrier may have been first breached by living beings about 150 million years ago. Some paleobiologists report that
computer model Computer simulation is the process of mathematical modelling, performed on a computer, which is designed to predict the behaviour of, or the outcome of, a real-world or physical system. The reliability of some mathematical models can be deter ...
s of their biomechanical capabilities suggest that certain long-tailed
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
s such as ''
Brontosaurus ''Brontosaurus'' (; meaning "thunder lizard" from Greek , "thunder" and , "lizard") is a genus of gigantic quadruped sauropod dinosaurs. Although the type species, ''B. excelsus'', had long been considered a species of the closely related ''A ...
'', ''
Apatosaurus ''Apatosaurus'' (; meaning "deceptive lizard") is a genus of herbivorous sauropod dinosaur that lived in North America during the Late Jurassic period. Othniel Charles Marsh described and named the first-known species, ''A. ajax'', in 1877, an ...
'', and ''
Diplodocus ''Diplodocus'' (, , or ) was a genus of diplodocid sauropod dinosaurs, whose fossils were first discovered in 1877 by S. W. Williston. The generic name, coined by Othniel Charles Marsh in 1878, is a neo-Latin term derived from Greek διπ ...
'' could flick their
tail The tail is the section at the rear end of certain kinds of animals’ bodies; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, r ...
s at supersonic speeds, creating a cracking sound. This finding is theoretical and disputed by others in the field.Wilford, John Noble.
"Did Dinosaurs Break the Sound Barrier?"
''The New York Times'', December 2, 1997. Retrieved: January 15, 2009.
Meteorite A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or Natural satellite, moon. When the ...
s in the Earth's
upper atmosphere Upper atmosphere is a collective term that refers to various layers of the atmosphere of the Earth above the troposphere and corresponding regions of the atmospheres of other planets, and includes: * The mesosphere, which on Earth lies between the ...
usually travel at higher than Earth's escape velocity, which is much faster than sound.


Early problems

The tip speed of
propeller A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon ...
blades depends on the propeller speed and the forward speed of the aircraft. When the aircraft speed is high enough, the tips reach supersonic speeds. Shock waves form at the blade tips and reduce how much of the shaft power driving the propeller is converted into the thrust force needed to move the aircraft. To fly faster, the engine power required to replace this loss, as well as to equal the increasing aircraft drag with speed, is so great that the size and weight of the engine becomes prohibitive. This speed limitation led to research into
jet engine A jet engine is a type of reaction engine discharging a fast-moving jet of heated gas (usually air) that generates thrust by jet propulsion. While this broad definition can include rocket, Pump-jet, water jet, and hybrid propulsion, the term ...
s, notably by
Frank Whittle Air Commodore Sir Frank Whittle, (1 June 1907 – 8 August 1996) was an English engineer, inventor and Royal Air Force (RAF) air officer. He is credited with inventing the turbojet engine. A patent was submitted by Maxime Guillaume in 1921 for ...
in England and
Hans von Ohain Hans Joachim Pabst von Ohain (14 December 191113 March 1998) was a German physicist, engineer, and the designer of the first operational jet engine. Together with Frank Whittle he is called the "father of the jet engine". His first test unit ran ...
in Germany. The jet engine is suitable for two reasons. It produces the required power, in terms of thrust, from a relatively small size compared to the piston engine it replaced. The whirling blades in the front of the jet engine are not adversely affected by high aircraft speeds in the same way as the propeller. Nevertheless, propeller aircraft ''were'' able to approach their
critical Mach number In aerodynamics, the critical Mach number (Mcr or M*) of an aircraft is the lowest Mach number at which the airflow over some point of the aircraft reaches the speed of sound, but does not exceed it.Clancy, L.J. ''Aerodynamics'', Section 11.6 At t ...
, different for each aircraft, in a dive. Unfortunately, doing so led to numerous crashes for a variety of reasons. Flying the
Mitsubishi Zero The Mitsubishi A6M "Zero" is a long-range carrier-based aircraft, carrier-based fighter aircraft formerly manufactured by Mitsubishi Aircraft Company, a part of Mitsubishi Heavy Industries, and was operated by the Imperial Japanese Navy from 19 ...
, pilots sometimes flew at full power into terrain because the rapidly 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. Likewise, the flexing caused by the low torsional stiffness of the
Supermarine Spitfire The Supermarine Spitfire is a British single-seat fighter aircraft used by the Royal Air Force and other Allied countries before, during, and after World War II. Many variants of the Spitfire were built, from the Mk 1 to the Rolls-Royce Grif ...
's wings caused them, in turn, to counteract aileron control inputs, leading to a condition known as ''
control reversal Control reversal is an adverse effect on the controllability of aircraft. The flight controls reverse themselves in a way that is not intuitive, so pilots may not be aware of the situation and therefore provide the wrong inputs; in order to roll to ...
''. This was solved in later models with changes to the wing. Worse still, a particularly dangerous interaction of the airflow between the wings and tail surfaces of diving
Lockheed P-38 Lightning The Lockheed P-38 Lightning is an American single-seat, twin piston-engined fighter aircraft that was used during World War II. Developed for the United States Army Air Corps by the Lockheed Corporation, the P-38 incorporated a distinctive twi ...
s made "pulling out" of dives difficult; however, the problem was later solved by the addition of a "dive flap" that upset the airflow under these circumstances. Flutter due to the formation of
shock wave In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a med ...
s on curved surfaces was another major problem, which led most famously to the breakup of a
de Havilland Swallow The de Havilland DH 108 "Swallow" was a British experimental aircraft designed by John Carver Meadows Frost in October 1945. The DH 108 featured a tailless, swept wing with a single vertical stabilizer, similar to the layout of the wartime Ge ...
and death of its pilot
Geoffrey de Havilland, Jr. Geoffrey Raoul de Havilland Jr., OBE (18 February 1910 – 27 September 1946) was a British test pilot. He was the son of Geoffrey de Havilland, the English aviation pioneer and aircraft designer. Early life Geoffrey Raoul de Havilland was b ...
on 27 September 1946. A similar problem is thought to have been the cause of the 1943 crash of the
BI-1 The Bereznyak-Isayev BI-1 was a Soviet short-range rocket powered interceptor developed during the Second World War. Early design Soviet research and development of rocket-powered aircraft began with Sergey Korolev's GIRD-6 project in 1932. Hi ...
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 routinely exceeded Mach 1, but aircraft designers and aerodynamicists during and after World War II discussed Mach 0.7 as a limit dangerous to exceed.


Early claims

During WWII and immediately 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 The airspeed indicator (ASI) or airspeed gauge is a flight instrument indicating the airspeed of an aircraft in kilometers per hour (km/h), knots (kn), miles per hour (MPH) and/or meters per second (m/s). The recommendation by ICAO is to use km/h, ...
(ASI) uses air pressure differences between two or more points on the aircraft, typically 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 also 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 remotely, normally 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 The Republic Aviation Corporation was an American aircraft manufacturer based in Farmingdale, New York, on Long Island, New York, Long Island. Originally known as the Seversky Aircraft Company, the company was responsible for the design and produc ...
issued a press release stating that Lts.
Harold E. Comstock Harold Elwood "Bunny" Comstock (20 December 1920 – 3 April 2009) was an American fighter ace in the 56th Fighter Group during World War II, and a career fighter pilot in the United States Air Force. After a test flight of the Republic P-47 Thun ...
and Roger Dyar had exceeded the speed of sound during test dives in a
Republic P-47 Thunderbolt The Republic P-47 Thunderbolt is a World War II-era fighter aircraft produced by the American company Republic Aviation from 1941 through 1945. It was a successful high-altitude fighter and it also served as the foremost American fighter-bombe ...
. It is widely agreed that this was due to inaccurate ASI readings. In similar tests, the
North American P-51 Mustang The North American Aviation P-51 Mustang is an American long-range, single-seat fighter aircraft, fighter and fighter-bomber used during World War II and the Korean War, among other conflicts. The Mustang was designed in April 1940 by a team ...
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 aircraft is the Mach 0.891 for a Spitfire PR XI, flown during dive tests at the Royal Aircraft Establishment, Farnborough in April 1944. The Spitfire, a
photo-reconnaissance Aerial reconnaissance is reconnaissance for a military or strategic purpose that is conducted using reconnaissance aircraft. The role of reconnaissance can fulfil a variety of requirements including artillery spotting, the collection of imag ...
variant, the Mark XI, fitted with an extended "rake type" multiple pitot system, was flown by Squadron Leader J. R. Tobin to this speed, corresponding to a corrected
true airspeed The true airspeed (TAS; also KTAS, for ''knots true airspeed'') of an aircraft is the speed of the aircraft relative to the air mass through which it is flying. The true airspeed is important information for accurate navigation of an aircraft. Tr ...
(TAS) of 606 mph. In a subsequent flight, Squadron Leader Anthony Martindale achieved Mach 0.92, but it ended in a forced landing after over-revving damaged the engine.
Hans Guido Mutke Hans Guido Mutke (25 March 1921 – 8 April 2004) was a fighter pilot for the German Luftwaffe during World War II. He was born in Nysa, Poland, Neisse, Upper Silesia (now Nysa, Poland). On 25 April 1945, Mutke landed at Dübendorf, Switzerl ...
claimed to have broken the sound barrier on 9 April 1945 in the
Messerschmitt Me 262 The Messerschmitt Me 262, nicknamed ''Schwalbe'' (German: "Swallow") in fighter versions, or ''Sturmvogel'' (German: "Storm Bird") in fighter-bomber versions, is a fighter aircraft and fighter-bomber that was designed and produced by the Germa ...
jet aircraft. He states that his ASI pegged itself at . Mutke reported not just transonic
buffeting Aeroelasticity is the branch of physics and engineering studying the interactions between the inertial, elastic, and aerodynamic forces occurring while an elastic body is exposed to a fluid flow. The study of aeroelasticity may be broadly classi ...
, but the resumption of normal control once a certain speed was exceeded, then a resumption of severe buffeting once the Me 262 slowed again. He also reported engine flame-out. This claim is widely disputed, even by pilots in his unit. All of the effects he reported are known to occur on the Me 262 at much lower speeds, and the ASI reading is simply not reliable in the transonic. Further, a series of tests made by Karl Doetsch at the behest of Willy Messerschmitt found that the plane became uncontrollable above Mach 0.86, and at Mach 0.9 would nose over into a dive that could not be recovered from. Post-war tests by the RAF confirmed these results, with the slight modification that the maximum speed using new instruments was found to be Mach 0.84, rather than Mach 0.86. In 1999, Mutke enlisted the help of Professor Otto Wagner of the Munich Technical University to run computational tests to determine whether the aircraft could break the sound barrier. These tests do not rule out the possibility, but are lacking accurate data on the coefficient of drag that would be needed to make accurate simulations. Wagner stated: "I don't want to exclude the possibility, but I can imagine he may also have been just below the speed of sound and felt the buffeting, but did not go above Mach-1." One bit of evidence presented by Mutke is on page 13 of the "Me 262 A-1 Pilot's Handbook" issued by Headquarters Air Materiel Command,
Wright Field Wilbur Wright Field was a military installation and an airfield used as a World War I pilot, mechanic, and armorer training facility and, under different designations, conducted United States Army Air Corps and Air Forces flight testing. Loca ...
, Dayton, Ohio as Report No. F-SU-1111-ND on January 10, 1946: The comments about restoration of flight control and cessation of buffeting above Mach 1 are very significant in a 1946 document. However, it is not clear where these terms came from, as it does not appear the US pilots carried out such tests. In his 1990 book ''Me-163'', former Messerschmitt Me 163 "Komet" pilot Mano Ziegler claims that his friend, test pilot
Heini Dittmar Heini Dittmar (Born March 30, 1912, Bad Kissingen, Unterfranken, Germany – Died April 28, 1960 near Mülheim an der Ruhr, West Germany) was a record-breaking German glider pilot. Inspired by the example of his glider flying brother Edgar, Dit ...
, broke the sound barrier while diving the rocket plane, and that several people on the ground heard the sonic booms. He claims that on 6 July 1944, Dittmar, flying Me 163B V18, bearing the alphabetic code VA+SP, was measured traveling at a speed of 1,130 km/h (702 mph). However, no evidence of such a flight exists in any of the materials from that period, which were captured by Allied forces and extensively studied. Dittmar had been officially recorded at 1,004.5 km/h (623.8 mph) in level flight on 2 October 1941 in the prototype Me 163A V4. He reached this speed at less than full throttle, as he was concerned by the transonic buffeting. Dittmar himself does not make a claim that he broke the sound barrier on that flight and notes that the speed was recorded only on the AIS. He does, however, take credit for being the first pilot to "knock on the sound barrier". The Luftwaffe test pilot
Lothar Sieber Lothar Sieber (7 April 1922 – 1 March 1945) was a German test pilot who was killed in the first vertical take-off manned rocket flight, in a Bachem Ba 349 "Natter". Before he became a test pilot for Bachem, he piloted an Arado Ar 232 in hig ...
(7 April 1922 – 1 March 1945) may have inadvertently become the first human to break the sound barrier on 1 March 1945. This occurred while he was piloting a
Bachem Ba 349 The Bachem Ba 349 Natter ( en, Colubrid, grass-snake) was a World War II German point-defence rocket-powered interceptor, which was to be used in a very similar way to a manned surface-to-air missile. After a vertical take-off, which eliminated ...
"Natter" for the first crewed vertical takeoff of a rocket in history. In 55 seconds, he traveled a total of 14 km (8.7 miles). The aircraft crashed, and he perished violently in this endeavor. There are a number of unmanned vehicles that flew at supersonic speeds during this period. In 1933, Soviet designers working on
ramjet A ramjet, or athodyd (aero thermodynamic duct), is a form of airbreathing jet engine that uses the forward motion of the engine to produce thrust. Since it produces no thrust when stationary (no ram air) ramjet-powered vehicles require an ass ...
concepts fired phosphorus-powered engines out of artillery guns to get them to operational speeds. It is possible that this produced supersonic performance as high as Mach 2, but this was not due solely to the engine itself. In contrast, the German
V-2 The V-2 (german: Vergeltungswaffe 2, lit=Retaliation Weapon 2), with the technical name ''Aggregat 4'' (A-4), was the world’s first long-range guided ballistic missile. The missile, powered by a liquid-propellant rocket engine, was develope ...
ballistic missile A ballistic missile is a type of missile that uses projectile motion to deliver warheads on a target. These weapons are guided only during relatively brief periods—most of the flight is unpowered. Short-range ballistic missiles stay within the ...
routinely broke the sound barrier in flight, for the first time on 3 October 1942. By September 1944, V-2s routinely achieved Mach 4 (1,200 m/s, or 3044 mph) during terminal descent.


Breaking the sound barrier

In 1942, the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...
's
Ministry of Aviation The Ministry of Aviation was a department of the United Kingdom government established in 1959. Its responsibilities included the regulation of civil aviation and the supply of military aircraft, which it took on from the Ministry of Supply. ...
began a top-secret project with
Miles Aircraft Miles was the name used between 1943 and 1947 to market the aircraft of British engineer Frederick George Miles, who, with his wife – aviator and draughtswoman Maxine "Blossom" Miles (née Forbes-Robertson) – and his brother George Herbert ...
to develop the world's first aircraft capable of breaking the sound barrier. The project resulted in the development of the prototype
Miles M.52 The Miles M.52 was a turbojet-powered supersonic research aircraft project designed in the United Kingdom in the mid-1940s. In October 1943, Miles Aircraft was issued with a contract to produce the aircraft in accordance with Air Ministry Sp ...
turbojet-powered aircraft, which was designed to reach 1,000 mph (417 m/s; 1,600 km/h) (over twice the existing speed record) in level flight, and to climb to an altitude of 36,000 ft (11 km) in 1 minute 30 seconds. A huge number of advanced features were incorporated into the resulting M.52 design, many of which hint at a detailed knowledge of
supersonic Supersonic speed is the speed of an object that exceeds the speed of sound ( Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately . Speeds greater than five times ...
aerodynamics Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dyn ...
. In particular, the design featured a conical nose and sharp wing leading edges, as it was known that round-nosed projectiles could not be stabilised at supersonic speeds. The design used very thin wings of biconvex section proposed by
Jakob Ackeret Jakob Ackeret, FRAeS (17 March 1898 – 27 March 1981) was a Swiss aeronautical engineer. He is widely viewed as one of the foremost aeronautics experts of the 20th century. Birth and education Jakob Ackeret was born in 1898 in Switzerland. He ...
for low drag. The wing tips were "clipped" to keep them clear of the
conical A cone is a three-dimensional geometric shape that tapers smoothly from a flat base (frequently, though not necessarily, circular) to a point called the apex or vertex. A cone is formed by a set of line segments, half-lines, or lines conn ...
shock wave In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a med ...
generated by the nose of the aircraft. The fuselage had the minimum cross-section allowable around the centrifugal engine with fuel tanks in a saddle over the top. Another critical addition was the use of a power-operated
stabilator A stabilator is a fully movable aircraft horizontal stabilizer. It serves the usual functions of longitudinal stability, control and stick force requirements otherwise performed by the separate parts of a conventional horizontal stabilizer and el ...
, also known as the all-moving tail or
flying tail A stabilator is a fully movable aircraft horizontal stabilizer. It serves the usual functions of longitudinal stability, control and stick force requirements otherwise performed by the separate parts of a conventional horizontal stabilizer and el ...
, a key to supersonic flight control, which contrasted with traditional hinged
tailplane A tailplane, also known as a horizontal stabiliser, is a small lifting surface located on the tail (empennage) behind the main lifting surfaces of a fixed-wing aircraft as well as other non-fixed-wing aircraft such as helicopters and gyroplane ...
s (horizontal stabilizers) connected mechanically to the pilots
control column A yoke, alternatively known as a control wheel or a control column, is a device used for piloting some fixed-wing aircraft.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 563. Aviation Supplies & Academics, 1997. ...
. Conventional control surfaces became ineffective at the high subsonic speeds then being achieved by fighters in dives, due to the aerodynamic forces caused by the formation of shockwaves at the hinge and the rearward movement of the centre of pressure, which together could override the control forces that could be applied mechanically by the pilot, hindering recovery from the dive.Brown, Eric (August–November 1980). "Miles M.52: The Supersonic Dream". ''Air Enthusiast Thirteen''. . A major impediment to early transonic flight was
control reversal Control reversal is an adverse effect on the controllability of aircraft. The flight controls reverse themselves in a way that is not intuitive, so pilots may not be aware of the situation and therefore provide the wrong inputs; in order to roll to ...
, the phenomenon which caused flight inputs (stick, rudder) to switch direction at high speed; it was the cause of many accidents and near-accidents. An
all-flying tail A stabilator is a fully movable aircraft horizontal stabilizer. It serves the usual functions of longitudinal stability, control and stick force requirements otherwise performed by the separate parts of a conventional horizontal stabilizer and el ...
is considered to be a minimum condition of enabling aircraft to break the transonic barrier safely, without losing pilot control. The Miles M.52 was the first instance of this solution, which has since been universally applied. Initially, the aircraft was to use
Frank Whittle Air Commodore Sir Frank Whittle, (1 June 1907 – 8 August 1996) was an English engineer, inventor and Royal Air Force (RAF) air officer. He is credited with inventing the turbojet engine. A patent was submitted by Maxime Guillaume in 1921 for ...
's latest engine, the Power Jets W.2/700, which would only reach supersonic speed in a shallow dive. To develop a fully supersonic version of the aircraft, an innovation incorporated was a ''reheat jetpipe'' – also known as an
afterburner An afterburner (or reheat in British English) is an additional combustion component used on some jet engines, mostly those on military supersonic aircraft. Its purpose is to increase thrust, usually for supersonic flight, takeoff, and comba ...
. Extra fuel was to be burned in the tailpipe to avoid overheating the turbine blades, making use of unused oxygen in the exhaust. Finally, the design included another critical element the use of a
shock cone Inlet cones (sometimes called shock cones or inlet centerbodies) are a component of some supersonic aircraft and missiles. They are primarily used on ramjets, such as the D-21 Tagboard and Lockheed X-7. Some turbojet aircraft including the Su ...
in the nose to slow the incoming air to the subsonic speeds needed by the engine. Although the project was eventually cancelled, the research was used to construct an unmanned missile that went on to achieve a speed of Mach 1.38 in a successful, controlled
transonic Transonic (or transsonic) flow is air flowing around an object at a speed that generates regions of both subsonic and supersonic airflow around that object. The exact range of speeds depends on the object's critical Mach number, but transonic ...
and
supersonic Supersonic speed is the speed of an object that exceeds the speed of sound ( Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately . Speeds greater than five times ...
level test flight; this was a unique achievement at that time, which validated the aerodynamics of the M.52. Meanwhile, test pilots achieved high velocities in the tailless,
swept-wing A swept wing is a wing that angles either backward or occasionally forward from its root rather than in a straight sideways direction. Swept wings have been flown since the pioneer days of aviation. Wing sweep at high speeds was first investigat ...
de Havilland DH 108 The de Havilland DH 108 "Swallow" was a British experimental aircraft designed by John Carver Meadows Frost in October 1945. The DH 108 featured a tailless, swept wing with a single vertical stabilizer, similar to the layout of the wartime ...
. One of them was
Geoffrey de Havilland, Jr. Geoffrey Raoul de Havilland Jr., OBE (18 February 1910 – 27 September 1946) was a British test pilot. He was the son of Geoffrey de Havilland, the English aviation pioneer and aircraft designer. Early life Geoffrey Raoul de Havilland was b ...
, who was killed on 27 September 1946 when his DH 108 broke up at about Mach 0.9.
John Derry Squadron leader John Douglas Derry DFC (5 December 1921 – 6 September 1952) was a British test pilot who is believed to be the first Briton to have exceeded the speed of sound in flight. Early life and education Derry was born in Cairo, ...
has been called "Britain's first supersonic pilot" because of a dive he made in a DH 108 on 6 September 1948.


The first aircraft to officially break the sound barrier

The British
Air Ministry The Air Ministry was a department of the Government of the United Kingdom with the responsibility of managing the affairs of the Royal Air Force, that existed from 1918 to 1964. It was under the political authority of the Secretary of State ...
signed an agreement with the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
to exchange all its high-speed research, data and designs and
Bell Aircraft The Bell Aircraft Corporation was an American aircraft manufacturer, a builder of several types of fighter aircraft for World War II but most famous for the Bell X-1, the first supersonic aircraft, and for the development and production of many ...
company was given access to the drawings and research on the M.52, but the U.S. reneged on the agreement, and no data was forthcoming in return. Bell's supersonic design was still using a conventional tail, and they were battling the problem of control. They utilized the information to initiate work on the
Bell X-1 The Bell X-1 (Bell Model 44) is a rocket engine–powered aircraft, designated originally as the XS-1, and was a joint National Advisory Committee for Aeronautics– U.S. Army Air Forces–U.S. Air Force supersonic research project built by Be ...
. The final version of the Bell X-1 was very similar in design to the original
Miles M.52 The Miles M.52 was a turbojet-powered supersonic research aircraft project designed in the United Kingdom in the mid-1940s. In October 1943, Miles Aircraft was issued with a contract to produce the aircraft in accordance with Air Ministry Sp ...
version. Also featuring the all-moving tail, the XS-1 was later known as the X-1. It was in the X-1 that
Chuck Yeager Brigadier General Charles Elwood Yeager ( , February 13, 1923December 7, 2020) was a United States Air Force officer, flying ace, and record-setting test pilot who in October 1947 became the first pilot in history confirmed to have exceeded the ...
was credited with being the first person to break the sound barrier in level flight on 14 October 1947, flying at an altitude of 45,000 ft (13.7 km). George Welch made a plausible but officially unverified claim to have broken the sound barrier on 1 October 1947, while flying an XP-86
Sabre A sabre ( French: sabʁ or saber in American English) is a type of backsword with a curved blade associated with the light cavalry of the early modern and Napoleonic periods. Originally associated with Central European cavalry such as th ...
. He also claimed to have repeated his supersonic flight on 14 October 1947, 30 minutes before Yeager broke the sound barrier in the Bell X-1. Although evidence from witnesses and instruments strongly imply that Welch achieved supersonic speed, the flights were not properly monitored and are not officially recognized. The XP-86 officially achieved supersonic speed on 26 April 1948. On 14 October 1947, just under a month after the United States Air Force had been created as a separate service, the tests culminated in the first crewed supersonic flight, piloted by Air Force Captain Charles "Chuck" Yeager in aircraft #46-062, which he had christened ''Glamorous Glennis''. The rocket-powered aircraft was launched from the bomb bay of a specially modified B-29 and glided to a landing on a runway. XS-1 flight number 50 is the first one where the X-1 recorded supersonic flight, with a maximum speed of Mach 1.06 (361 m/s, 1,299 km/h, 807.2 mph). As a result of the X-1's initial supersonic flight, the National Aeronautics Association voted its 1947 Collier Trophy to be shared by the three main participants in the program. Honored at the White House by President Harry S. Truman were Larry Bell for Bell Aircraft, Captain Yeager for piloting the flights, and John Stack for the
NACA The National Advisory Committee for Aeronautics (NACA) was a United States federal agency founded on March 3, 1915, to undertake, promote, and institutionalize aeronautical research. On October 1, 1958, the agency was dissolved and its assets ...
contributions. Jackie Cochran was the first woman to break the sound barrier, which she did on 18 May 1953, piloting a plane borrowed from the
Royal Canadian Air Force The Royal Canadian Air Force (RCAF; french: Aviation royale canadienne, ARC) is the air and space force of Canada. Its role is to "provide the Canadian Forces with relevant, responsive and effective airpower". The RCAF is one of three environm ...
, with Yeager accompanying her. On December 3, 1957,
Margaret Chase Smith Margaret Madeline Smith (née Chase; December 14, 1897 – May 29, 1995) was an American politician. A member of the Republican Party, she served as a U.S. representative (1940–1949) and a U.S. senator (1949–1973) from Maine. She was the firs ...
became the first woman in Congress to break the sound barrier, which she did as a passenger in an
F-100 Super Sabre The North American F-100 Super Sabre is an American supersonic jet fighter aircraft that served with the United States Air Force (USAF) from 1954 to 1971 and with the Air National Guard (ANG) until 1979. The first of the Century Series of ...
piloted by Air Force Major Clyde Good. In the late 1950s, Allen Rowley, a British journalist, was able to fly in a Super Sabre at 1000mph one of the few non-American civilians to exceed the speed of sound and one of the few civilians anywhere to make such a trip. On 21 August 1961, a Douglas DC-8-43 (registration N9604Z) unofficially exceeded Mach 1 in a controlled dive during a test flight at Edwards Air Force Base, as observed and reported by the flight crew; the crew were William Magruder (pilot), Paul Patten (co-pilot), Joseph Tomich (flight engineer), and Richard H. Edwards (flight test engineer). This was the first supersonic flight by a civilian airliner, achieved before the
Concorde The Aérospatiale/BAC Concorde () is a retired Franco-British supersonic airliner jointly developed and manufactured by Sud Aviation (later Aérospatiale) and the British Aircraft Corporation (BAC). Studies started in 1954, and France an ...
or the
Tu-144 The Tupolev Tu-144 (russian: Tyполев Ту-144; NATO reporting name: Charger) is a Soviet supersonic airliner, supersonic passenger airliner designed by Tupolev in operation from 1968 to 1999. The Tu-144 was the world's first commercial sup ...
flew.


The sound barrier understood

As the science of high-speed flight became more widely understood, a number of changes led to the eventual understanding that the "sound barrier" is easily penetrated, with the right conditions. Among these changes were the introduction of thin
swept wing A swept wing is a wing that angles either backward or occasionally forward from its root rather than in a straight sideways direction. Swept wings have been flown since the pioneer days of aviation. Wing sweep at high speeds was first investigate ...
s, the
area rule The Whitcomb area rule, named after NACA engineer Richard Whitcomb and also called the transonic area rule, is a design procedure used to reduce an aircraft's drag at transonic speeds which occur between about Mach 0.75 and 1.2. For supersonic ...
, and engines of ever-increasing performance. By the 1950s, many combat aircraft could routinely break the sound barrier in level flight, although they often suffered from control problems when doing so, such as
Mach tuck Mach tuck is an aerodynamic effect whereby the nose of an aircraft tends to pitch downward as the airflow around the wing reaches supersonic speeds. This diving tendency is also known as tuck under. The aircraft will first experience this effect ...
. Modern aircraft can transit the "barrier" without control problems. By the late 1950s, the issue was so well understood that many companies started investing in the development of supersonic airliners, or SSTs, believing that to be the next "natural" step in airliner evolution. However, this has not yet happened. Although the
Concorde The Aérospatiale/BAC Concorde () is a retired Franco-British supersonic airliner jointly developed and manufactured by Sud Aviation (later Aérospatiale) and the British Aircraft Corporation (BAC). Studies started in 1954, and France an ...
and the
Tupolev Tu-144 The Tupolev Tu-144 (russian: Tyполев Ту-144; NATO reporting name: Charger) is a Soviet supersonic passenger airliner designed by Tupolev in operation from 1968 to 1999. The Tu-144 was the world's first commercial supersonic transport ai ...
entered service in the 1970s, both were later retired without being replaced by similar designs. The last flight of a Concorde in service was in 2003. Although Concorde and the Tu-144 were the first aircraft to carry commercial passengers at supersonic speeds, they were not the first or only commercial airliners to break the sound barrier. On 21 August 1961, a
Douglas DC-8 The Douglas DC-8 (sometimes McDonnell Douglas DC-8) is a long-range narrow-body airliner built by the American Douglas Aircraft Company. After losing the May 1954 US Air Force tanker competition to the Boeing KC-135, Douglas announced in Ju ...
broke the sound barrier at Mach 1.012, or 1,240 km/h (776.2 mph), while in a controlled dive through 41,088 feet (12,510 m). The purpose of the flight was to collect data on a new design of leading edge for the wing.


Breaking the sound barrier in a land vehicle

On 12 January 1948, a Northrop unmanned rocket sled became the first land vehicle to break the sound barrier. At a military test facility at
Muroc Air Force Base Edwards Air Force Base (AFB) is a United States Air Force installation in California. Most of the base sits in Kern County, but its eastern end is in San Bernardino County and a southern arm is in Los Angeles County. The hub of the base is Ed ...
(now
Edwards AFB Edwards Air Force Base (AFB) is a United States Air Force installation in California. Most of the base sits in Kern County, but its eastern end is in San Bernardino County and a southern arm is in Los Angeles County. The hub of the base is Ed ...
),
California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...
, it reached a peak speed of 1,019 mph (1,640 km/h) before jumping the rails."A rocket powered sled runs along the ground on the rails in Muroc"
. ''Universal International News'', January 22, 1948. Retrieved: September 9, 2011.
On 15 October 1997, in a vehicle designed and built by a team led by
Richard Noble Richard James Anthony Noble, OBE (born 6 March 1946) is a Scottish entrepreneur who was holder of the land speed record between 1983 and 1997. He was also the project director of ThrustSSC, the vehicle which holds the current land speed record ...
,
Royal Air Force The Royal Air Force (RAF) is the United Kingdom's air and space force. It was formed towards the end of the First World War on 1 April 1918, becoming the first independent air force in the world, by regrouping the Royal Flying Corps (RFC) and ...
pilot Andy Green became the first person to break the sound barrier in a land vehicle in compliance with
Fédération Internationale de l'Automobile The Fédération Internationale de l'Automobile (FIA; en, International Automobile Federation) is an association established on 20 June 1904 to represent the interests of motoring organisations and motor car users. It is the governing body for ...
rules. The vehicle, called the
ThrustSSC ThrustSSC, Thrust SSC or Thrust SuperSonic Car is a British jet car developed by Richard Noble, Glynne Bowsher, Ron Ayers, and Jeremy Bliss. Thrust SSC holds the world land speed record, set on 15 October 1997, and driven by Andy Green, w ...
("Super Sonic Car"), captured the record 50 years and one day after
Yeager Yeager is a mostly American surname, a phonetic transcription of the common German surname Jaeger (Jäger), meaning hunter. Ya ...
's first supersonic flight.


Breaking the sound barrier as a human projectile


Felix Baumgartner

In October 2012
Felix Baumgartner Felix Baumgartner (; born 20 April 1969) is an Austrian skydiver, daredevil and BASE jumper. He is widely known for jumping to Earth from a helium balloon from the stratosphere on 14 October 2012 and landing in New Mexico, United States, as par ...
, with a team of scientists and sponsor Red Bull, attempted the highest sky-dive on record. The project would see Baumgartner attempt to jump 120,000 ft (36,580 m) from a helium balloon and become the first parachutist to break the sound barrier. The launch was scheduled for 9 October 2012, but was aborted due to adverse weather; subsequently the capsule was launched instead on 14 October. Baumgartner's feat also marked the 65th anniversary of U.S. test pilot
Chuck Yeager Brigadier General Charles Elwood Yeager ( , February 13, 1923December 7, 2020) was a United States Air Force officer, flying ace, and record-setting test pilot who in October 1947 became the first pilot in history confirmed to have exceeded the ...
's successful attempt to break the sound barrier in an aircraft. Baumgartner landed in eastern New Mexico after jumping from a world record 128,100 feet (39,045 m), or 24.26 miles, and broke the sound barrier as he traveled at speeds up to 833.9 mph (1342 km/h, or Mach 1.26). In the press conference after his jump, it was announced that he was in freefall for 4 minutes 18 seconds, the second longest freefall after the 1960 jump of
Joseph Kittinger Joseph William Kittinger II (July 27, 1928 – December 9, 2022) served as a United States Air Force (USAF) officer from 1950 to 1978. He was a fighter pilot who earned Command Pilot status and retired as a colonel. He held the world record for ...
for 4 minutes 36 seconds.Sunseri, Gina and Kevin Doak
"Felix Baumgartner: Daredevil Lands on Earth After Record Breaking Supersonic Leap"
. ''ABC News'', October 14, 2012.


Alan Eustace

In October 2014,
Alan Eustace Robert Alan Eustace (born 1956/1957) is an American computer scientist who served as Senior Vice President of Engineering at Google until retiring in 2015. On October 24, 2014, he made a free-fall jump from the stratosphere, breaking Felix Baum ...
, a senior vice president at
Google Google LLC () is an American multinational technology company focusing on search engine technology, online advertising, cloud computing, computer software, quantum computing, e-commerce, artificial intelligence, and consumer electronics. ...
, broke Baumgartner's record for highest sky-dive and also broke the sound barrier in the process.John Markoff
"Alan Eustace Jumps From Stratosphere, Breaking Felix Baumgartner’s World Record"
. ''New York Times''. October 24, 2014.
However, because Eustace's jump involved a
drogue parachute A drogue parachute is a parachute designed for deployment from a rapidly-moving object. It can be used for various purposes, such as to decrease speed, to provide control and stability, or as a pilot parachute to deploy a larger parachute. ...
, while Baumgartner's did not, their vertical speed and free-fall distance records remain in different categories.


Legacy

David Lean Sir David Lean (25 March 190816 April 1991) was an English film director, producer, screenwriter and editor. Widely considered one of the most important figures in British cinema, Lean directed the large-scale epics ''The Bridge on the River ...
directed ''
The Sound Barrier ''The Sound Barrier'' is a 1952 British aviation drama film directed by David Lean. It is a fictional story about attempts by aircraft designers and test pilots to break the sound barrier. It was David Lean's third and final film with his wife ...
'', a fictionalized retelling of the de Havilland DH 108 test flights.


See also

*
Sonic boom A sonic boom is a sound associated with shock waves created when an object travels through the air faster than the speed of sound. Sonic booms generate enormous amounts of sound energy, sounding similar to an explosion or a thunderclap to t ...
*
Vapor cone A vapor cone (also known as a Mach diamond, shock collar, or shock egg) is a visible cloud of condensed water that can sometimes form around an object moving at high speed through moist air, for example, an aircraft flying at transonic speeds. W ...


References


Notes


Citations


Bibliography

* "Breaking the Sound Barrier." ''
Modern Marvels ''Modern Marvels'' is an American worldwide television series that formerly aired on the History Channel and is currently shown on Story Television. The program focuses on how technologies affect and are used in modern society. It is History's f ...
(TV program)''. July 16, 2003. * Hallion, Dr. Richard P. "Saga of the Rocket Ships." ''AirEnthusiast Five'', November 1977 – February 1978. Bromley, Kent, UK: Pilot Press Ltd., 1977. * Miller, Jay. ''The X-Planes: X-1 to X-45,'' Hinckley, UK: Midland, 2001. . * Pisano, Dominick A., R. Robert van der Linden and Frank H. Winter. ''Chuck Yeager and the Bell X-1: Breaking the Sound Barrier''. Washington, DC: Smithsonian National Air and Space Museum (in association with Abrams, New York), 2006. . * Radinger, Willy and Walter Schick. ''Me 262'' (in German). Berlin: Avantic Verlag GmbH, 1996. . * Rivas, Brian (2012), ''A Very British Sound Barrier: DH 108, A Story of Courage, Triumph and Tragedy'',
Walton-on-Thames Walton-on-Thames, locally known as Walton, is a market town on the south bank of the Thames in the Elmbridge borough of Surrey, England. Walton forms part of the Greater London built-up area, within the KT postcode and is served by a wide ran ...
,
Surrey Surrey () is a ceremonial and non-metropolitan county in South East England, bordering Greater London to the south west. Surrey has a large rural area, and several significant urban areas which form part of the Greater London Built-up Area. ...
: Red Kite, . * Winchester, Jim. "Bell X-1." ''Concept Aircraft: Prototypes, X-Planes and Experimental Aircraft'' (The Aviation Factfile). Kent, UK: Grange Books plc, 2005. . * Wolfe. Tom. ''The Right Stuff''. New York: Farrar, Straus and Giroux, 1979. . * Yeager, Chuck, Bob Cardenas, Bob Hoover, Jack Russell and James Young. ''The Quest for Mach One: A First-Person Account of Breaking the Sound Barrier''. New York: Penguin Studio, 1997. . * Yeager, Chuck and Leo Janos. ''Yeager: An Autobiography''. New York: Bantam, 1986. .


External links


Fluid Mechanics
a collection of tutorials by Dr. Mark S. Cramer, Ph.D *

' by Carl Rod Nave, Ph.D
a video
of a
Concorde The Aérospatiale/BAC Concorde () is a retired Franco-British supersonic airliner jointly developed and manufactured by Sud Aviation (later Aérospatiale) and the British Aircraft Corporation (BAC). Studies started in 1954, and France an ...
reaching Mach 1 at intersection TESGO taken from below
An interactive Java applet
illustrating the sound barrier. {{DEFAULTSORT:Sound Barrier Airspeed Articles containing video clips
Barrier A barrier or barricade is a physical structure which blocks or impedes something. Barrier may also refer to: Places * Barrier, Kentucky, a community in the United States * Barrier, Voerendaal, a place in the municipality of Voerendaal, Netherl ...
de:Überschallflug#Schallmauer