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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. When the localized air pressure around the object drops, so does the air temperature. If the temperature drops below the saturation temperature, a cloud forms.
In the case of aircraft, the cloud is caused by expansion fans decreasing the air pressure, density, and temperature below the
File:Ares1-X(28OCT2009).jpg,
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. When the localized air pressure around the object drops, so does the air temperature. If the temperature drops below the saturation temperature, a cloud forms.
In the case of aircraft, the cloud is caused by expansion fans decreasing the air pressure, density, and temperature below the dew point
The dew point is the temperature to which air must be cooled to become saturated with water vapor, assuming constant air pressure and water content. When cooled below the dew point, moisture capacity is reduced and airborne water vapor will ...
. Then pressure, density, and temperature suddenly increase across the stern shock wave associated with a return to subsonic flow behind the aircraft. Since the local Mach number
Mach number (M or Ma) (; ) is a dimensionless quantity in fluid dynamics representing the ratio of flow velocity past a boundary to the local speed of sound.
It is named after the Moravian physicist and philosopher Ernst Mach.
: \mathrm = \f ...
is not uniform over the aircraft, parts of the aircraft may be supersonic while others remain subsonic—a flight regime called 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 transoni ...
flight.
In addition to making the shock waves themselves visible, water condensation can also occur in the trough between two crests of the shock waves produced by the passing of the object. However, this effect does not necessarily coincide with the acceleration of an aircraft through the speed of sound or Mach 1.
Examples
Thesecondensation cloud
A transient condensation cloud, also called a Wilson cloud, is observable surrounding large explosions in humid air.
When a nuclear weapon or a large amount of a conventional explosive is detonated in sufficiently humid air, the "negative phas ...
s can often be seen appearing around space-bound rockets as they accelerate through the atmosphere. For example, they were frequently seen during Space Shuttle
The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program n ...
launches, about 25 to 33 seconds after launch, when the vehicle was traveling at transonic speeds. Similar effects were also visible in archival footage of some nuclear test
Nuclear weapons tests are experiments carried out to determine nuclear weapons' effectiveness, Nuclear weapon yield, yield, and explosive capability. Testing nuclear weapons offers practical information about how the weapons function, how detona ...
s.
Gallery
Ares I-X
Ares I-X was the first-stage prototype and design concept demonstrator of Ares I, a launch system for human spaceflight developed by the National Aeronautics and Space Administration (NASA). Ares I-X was successfully launched on October 28, ...
test rocket during launch October 28, 2009
File:FA-18 Hornet breaking sound barrier (7 July 1999).jpg, F/A-18A at transonic speed
File:F-A-18C Hornet in transonic flight, with condensation cones.jpg, Complex set of condensation cones surrounds a F/A-18C
The McDonnell Douglas F/A-18 Hornet is an all-weather, twinjet, twin-engine, supersonic aircraft, supersonic, carrier-based aircraft, carrier-capable, Multirole combat aircraft, multirole combat aircraft, designed as both a Fighter aircraft, ...
at transonic speed
File:F-35 with double vapor cone, 2016 airshow RNAF, Leeuwarden.jpg, F-35
The Lockheed Martin F-35 Lightning II is an American family of single-seat, single-engine, all-weather stealth multirole combat aircraft that is intended to perform both air superiority and strike missions. It is also able to provide elect ...
with a double vapor cone
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 ...
*Sound barrier
The sound barrier or sonic barrier is the large increase in aerodynamic drag and other undesirable effects experienced by an aircraft or other object when it approaches the speed of sound. When aircraft first approached the speed of sound, th ...
*Shock diamond
Shock diamonds (also known as Mach diamonds or thrust diamonds) are a formation of standing wave patterns that appear in the supersonic exhaust plume of an aerospace propulsion system, such as a supersonic jet engine, rocket, ramjet, or scramjet ...
*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 me ...
*Contrail
Contrails (; short for "condensation trails") or vapor trails are line-shaped clouds produced by aircraft engine exhaust or changes in air pressure, typically at aircraft cruising altitudes several miles above the Earth's surface. Contrails ar ...
*Condensation cloud
A transient condensation cloud, also called a Wilson cloud, is observable surrounding large explosions in humid air.
When a nuclear weapon or a large amount of a conventional explosive is detonated in sufficiently humid air, the "negative phas ...
* Prandtl–Glauert singularity
*Condensation
Condensation is the change of the state of matter from the gas phase into the liquid phase, and is the reverse of vaporization. The word most often refers to the water cycle. It can also be defined as the change in the state of water vapo ...
References
Further reading
*External links
* *{{YouTube, -mr9tam_c9g, F-18 Hornet High-speed (transonic) flyby Shock waves