Sunday, May 31, 2009

Cloud Forms Around as F-18 Approaches the Speed of Sound

I think this is a remarkable photo. 

This Navy F-18 Super Hornet forms a water vapor cone as air cools due to the pressure drop around the jet. Air cools when it expands into the lower pressure region, and that forms a cloud.  When the jet passes the speed of sound, the air flow is more turbulent and the cone is less apparent. This cone only occurs when the relative humidity is right, and at a narrow range in speed.

 The cone is also called a " shock collar" -- obviously a different kind than the "shock collar" a dog wears.