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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, such as 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
File:Ares1-X(28OCT2009).jpg, Ares I-X 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 at transonic speed
File:F-35 with double vapor cone, 2016 airshow RNAF, Leeuwarden.jpg, F-35 with a double 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, such as 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
Saturation, saturated, unsaturation or unsaturated may refer to:
Chemistry
*Saturated and unsaturated compounds, a classification of compounds related to their ability to resist addition reactions
** Degree of unsaturation
**Saturated fat or satu ...
, 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 the air needs to be cooled to (at constant pressure) in order to produce a relative humidity of 100%. This temperature depends on the pressure and water content of the air. When the air at a temperature above the ...
. 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
The Mach number (M or Ma), often only Mach, (; ) 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 Austrian physicist and philosopher Erns ...
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 speed, supersonic airflow around that object. The exact range of speeds depends on the object's critical Mach numb ...
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
These condensation clouds can often be seen appearing around space-bound rockets as they accelerate through the atmosphere. For example, they were frequently seen duringSpace Shuttle
The Space Shuttle is a retired, partially reusable launch system, 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. ...
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 the performance of nuclear weapons and the effects of their explosion. Nuclear testing is a sensitive political issue. Governments have often performed tests to signal strength. Bec ...
s.
Gallery
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, and less commonly Mach disks) are a formation of standing wave patterns that appear in the supersonic exhaust plume of an aerospace propulsion system, such as a supersonic jet engi ...
*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 vapour trails are line-shaped clouds produced by aircraft engine exhaust or changes in air pressure, typically at aircraft cruising altitudes several kilometres/miles above the Earth's surface. ...
* Condensation cloud
* 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 vapor ...
References
Further reading
*External links
* *{{YouTube, -mr9tam_c9g, F-18 Hornet High-speed (transonic) flyby Aircraft aerodynamics Shock waves