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Supersonic speed

From Wikipedia, the free encyclopedia
(Redirected fromSupersonic)
Speed that exceeds the speed of sound
"Supersonic" redirects here. For other uses, seeSupersonic (disambiguation).
AUnited States NavyF/A-18F Super Hornet intransonicflight
U.S. NavyF/A-18 approaching the speed of sound. The white cloud forms as a result of thesupersonic expansion fans dropping the air temperature below thedew point.[1][2]

Supersonic speed is the speed of an object that exceeds thespeed of sound (Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) atsea level, this speed is approximately 343.2 m/s (1,126 ft/s; 768 mph; 667.1 kn; 1,236 km/h). Speeds greater than five times the speed of sound (Mach 5) are often referred to ashypersonic. Flights during which only some parts of the air surrounding an object, such as the ends of rotor blades, reach supersonic speeds are calledtransonic. This occurs typically somewhere between Mach 0.8 and Mach 1.2.

Sounds are traveling vibrations in the form of pressure waves in an elastic medium. Objects move at supersonic speed when the objects move faster than the speed at which sound propagates through the medium. In gases, sound travels longitudinally at different speeds, mostly depending on themolecular mass andtemperature of the gas, andpressure has little effect. Since air temperature and composition varies significantly with altitude, the speed of sound, andMach numbers for a steadily moving object may change. In water atroom temperature supersonic speed means any speed greater than 1,440 m/s (4,724 ft/s). In solids, sound waves can be polarized longitudinally or transversely and have higher velocities.

Supersonic fracture is crack formation faster than the speed of sound in abrittle material.

Early meaning

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The word supersonic comes from twoLatin derived words; 1)super: above and 2)sonus: sound, which together mean above sound, or faster than sound.

At the beginning of the 20th century, the term "supersonic" was used as an adjective to describe sound whose frequency is above the range of normal human hearing. The modern term for this meaning is "ultrasonic", but the older meaning sometimes still lives on, as in the wordsuperheterodyne

Supersonic objects

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British AirwaysConcorde in early BA livery atLondon-Heathrow Airport, in the early 1980s

The tip of abullwhip is generally seen as the first object designed to reach the speed of sound. This action results in its telltale "crack", which is actually just asonic boom. The first human-made supersonic boom was likely caused by a piece of common cloth, leading to the whip's eventual development.[3] It's thewave motion travelling through the bullwhip that makes it capable of achieving supersonic speeds.[4][5]

Most modernfirearmbullets are supersonic, with rifleprojectiles often travelling at speeds approaching and in some cases[6] well exceedingMach 3.

Mostspacecraft are supersonic at least during portions of their reentry, though the effects on the spacecraft are reduced by low air densities. During ascent, launch vehicles generally avoid going supersonic below 30 km (~98,400 feet) to reduce air drag.

Note that thespeed of sound decreases somewhat with altitude, due to lower temperatures found there (typically up to 25 km). At even higher altitudes the temperature starts increasing, with the corresponding increase in the speed of sound.

When an inflatedballoon is burst, the torn pieces oflatex contract at supersonic speed, which contributes to the sharp and loud popping noise.

Supersonic land vehicles

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To date, only one land vehicle has officially travelled at supersonic speed, theThrustSSC. The vehicle, driven byAndy Green, holds the world land speed record, having achieved an average speed on its bi-directional run of 1,228 km/h (763 mph) in theBlack Rock Desert on 15 October 1997.

TheBloodhound LSR project planned an attempt on the record in 2020 atHakskeenpan in South Africa with a combination jet and hybrid rocket propelled car. The aim was to break the existing record, then make further attempts during which (the members of) the team hoped to reach speeds of up to 1,600 km/h (1,000 mph). The effort was originally run byRichard Noble who was the leader of the ThrustSSC project, however following funding issues in 2018, the team was bought byIan Warhurst and renamed Bloodhound LSR. Later the project was indefinitely delayed due to theCOVID-19 pandemic and the vehicle was put up for sale.

Supersonic flight

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Main article:Supersonic aircraft

Most modernfighter aircraft are supersonic aircraft. No modern-day passenger aircraft are capable of supersonic speed, but there have beensupersonic passenger aircraft, namelyConcorde and theTupolev Tu-144. Both of these passengeraircraft and some modern fighters are also capable ofsupercruise, a condition of sustained supersonic flight without the use of anafterburner. Due to its ability to supercruise for several hours and the relatively high frequency of flight over several decades, Concorde spent more time flying supersonically than all other aircraft combined by a considerable margin. Since Concorde's final retirement flight on November 26, 2003, there are no supersonic passenger aircraft left in service. Some largebombers, such as theTupolev Tu-160 andRockwell B-1 Lancer are also supersonic-capable.

Theaerodynamics ofsupersonic aircraft is simpler than subsonic aerodynamics because the airsheets at different points along the plane often cannot affect each other. Supersonic jets and rocket vehicles require several times greater thrust to push through the extraaerodynamic drag experienced within thetransonic region (around Mach 0.85–1.2). At these speedsaerospace engineers can gently guide air around thefuselage of the aircraft without producing newshock waves, but any change in cross area farther down the vehicle leads to shock waves along the body. Designers use theSupersonic area rule and theWhitcomb area rule to minimize sudden changes in size.

The sound source is traveling at 1.4 times the speed of sound, c (Mach 1.4). Because the source is moving faster than the sound waves it creates, it actually leads the advancing wavefront. The sound source will pass by a stationary observer before the observer actually hears the sound it creates.
Conical shockwave with its hyperbola-shaped ground contact zone in yellow

However, in practical applications, a supersonic aircraft must operate stably in both subsonic and supersonic profiles, hence aerodynamic design is more complex.

The main key to having low supersonic drag is to properly shape the overall aircraft to be long and thin, and close to a "perfect" shape, thevon Karman ogive orSears-Haack body. This has led to almost every supersonic cruising aircraft looking very similar to every other, with a very long and slender fuselage and large delta wings, cf.SR-71,Concorde, etc. Although not ideal for passenger aircraft, this shaping is quite adaptable for bomber use.

See also

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References

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  1. ^"APOD: 2007 August 19 - A Sonic Boom".antwrp.gsfc.nasa.gov.
  2. ^"F-14 CONDENSATION CLOUD IN ACTION".www.eng.vt.edu. Archived fromthe original on 2004-06-02.
  3. ^"Does the Tip of a Snapped Towel Travel Faster Than Sound?".
  4. ^Mike May (2002)."Crackin' Good Mathematics".American Scientist.90 (5). Archived fromthe original on 2016-03-22. Retrieved2015-08-26.
  5. ^"Hypography – Science for everyone – Whip Cracking Mystery Explained". Archived fromthe original on 2012-02-17. Retrieved2008-02-06.
  6. ^"Hornady Ammunition Charts"(PDF). Archived fromthe original(PDF) on 2007-09-27. Retrieved2011-11-04.

External links

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