Film, Media & TV0 min ago
Aircraft: Freeze Or Fry?
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At 10 000 m altitude a balloon is cold, but a meteor is hot. What would be the temperature of the nose of an aircraft flying at (say) 600 km/h? Ignore conduction and radiation, or masochists can assume an infinite block of Aluminium with a thin layer of light grey paint with a reflectance of 50 %. I assume that the temperature given on the displays in long-distance flights is “balloon” temperature.
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Oooh! Fun! The answer is that the nose will rise by 30-40°C due to frictional losses, but since the external temp at that altitude is about -54°C, so the outer surface is still well below zero. A meteorite is travelling at supersonic speeds, and the shock waves around the object, as well as the frictional losses in the atmosphere create lots of drag, and this...
10:40 Fri 16th Mar 2018
Oooh! Fun!
The answer is that the nose will rise by 30-40°C due to frictional losses, but since the external temp at that altitude is about -54°C, so the outer surface is still well below zero.
A meteorite is travelling at supersonic speeds, and the shock waves around the object, as well as the frictional losses in the atmosphere create lots of drag, and this is expressed as energy, resulting in higher temperatures of both the air that encounters the meteorite and the main body of the meteorite.
Essentially some of the kinetic energy of the meteorite is converted to heat.
In fact it is mostly apparent on the body of the meteorite, since the air is in contact for only a short time.
With an airliner, first, the speeds are sub-sonic, so the frictional losses are much less, because there are no trans-sonic shock waves.
Second, the airliner's shape is designed to minimise losses due to friction and hence frictional heating.
However the skin heating on Concorde and other supersonic aircraft is significant.
I think the SR-71 (US spy plane - sorry, "strategic reconnaissance") has issues with the skin becoming over-heated when flying at Mach 3 and above. That's maybe why the skin was painted black, to increase radiation cooling.
My father worked in the Aero environment during the development of Concorde and I remember discussions about skin friction and potential over-heating on that aircraft.
Hope it helps
The answer is that the nose will rise by 30-40°C due to frictional losses, but since the external temp at that altitude is about -54°C, so the outer surface is still well below zero.
A meteorite is travelling at supersonic speeds, and the shock waves around the object, as well as the frictional losses in the atmosphere create lots of drag, and this is expressed as energy, resulting in higher temperatures of both the air that encounters the meteorite and the main body of the meteorite.
Essentially some of the kinetic energy of the meteorite is converted to heat.
In fact it is mostly apparent on the body of the meteorite, since the air is in contact for only a short time.
With an airliner, first, the speeds are sub-sonic, so the frictional losses are much less, because there are no trans-sonic shock waves.
Second, the airliner's shape is designed to minimise losses due to friction and hence frictional heating.
However the skin heating on Concorde and other supersonic aircraft is significant.
I think the SR-71 (US spy plane - sorry, "strategic reconnaissance") has issues with the skin becoming over-heated when flying at Mach 3 and above. That's maybe why the skin was painted black, to increase radiation cooling.
My father worked in the Aero environment during the development of Concorde and I remember discussions about skin friction and potential over-heating on that aircraft.
Hope it helps
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