Temperature Rise with speed
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Still on feet, moving with metres or just sitting down?
G'Day Podeans and Auntie Podeans alike!
It isn't thermodynamics prompting my drift but the argument whether or not Ramanjuan has supremacy over Gauss when it comes to basic geodesy. A grave error was made when the international nautical mile was redefined. An error of 4.1045 Clarke feet.
I'm not saying any good maths undergraduate can blow apart the argument that perimeter is more important than surface area if it comes to modelling the earth as a smooth ellipsoid. Any child with a computer and access to the web can do the same.
In fact I first heard the argument in a pub where the matter under discussion was what would be the visible difference if God spliced an extra yard into a hoop which he had already fashioned to girdle the earth. Try it with a sphere of radius 20901500 feet for simplicity. Amazing! What was a tight fight before now has a clearance of five-and-three-quarter inches.
This proves that scientific definitions are best made with feet not metres, upon a bar, not of temperature controlled platinum but ice-cold Tooheys, Redback, Swan, Gage's or whatever is currently on offer at the The Lucky Shag in Barrack St Perth WA over the festive season. (Bring your own cormorant, it's that kind Shag).
Ron Hatch of GPS is correct. If anyone is looking for a better-fit, intellectual honesty, sounder mathematics and accurate cartography the best offer for the nautical mile is 6080.22ft. Which is coincidentally the old Admiralty Mile of Clarke, Bamford, Gauss, Andoyer, Weems and Lambert. But to redefine the nautical mile back more or less to what it was because t'committee goofed and got the form of the earth sized wrong would lead to too many red faces rather than Two Too many Toohey's.
Jeppesens are proud of their accuracy drawn to a scale of 1 inch to the old nautical mile. God went one better at twelve inches to the foot. Hatch has surveyed it and says the old boys with their glass and brass made a better fist of it than the bunch of academics in Bermuda. He also positions his satellites with a theory suggestive that Einstein didn't quite get everything right. (See his Ether Gage Theory). And now to raise the temperature of my next stubbie by one degree, how fast must my hand move again?
Festive Chiz
Mr and Mrs "E"
It isn't thermodynamics prompting my drift but the argument whether or not Ramanjuan has supremacy over Gauss when it comes to basic geodesy. A grave error was made when the international nautical mile was redefined. An error of 4.1045 Clarke feet.
I'm not saying any good maths undergraduate can blow apart the argument that perimeter is more important than surface area if it comes to modelling the earth as a smooth ellipsoid. Any child with a computer and access to the web can do the same.
In fact I first heard the argument in a pub where the matter under discussion was what would be the visible difference if God spliced an extra yard into a hoop which he had already fashioned to girdle the earth. Try it with a sphere of radius 20901500 feet for simplicity. Amazing! What was a tight fight before now has a clearance of five-and-three-quarter inches.
This proves that scientific definitions are best made with feet not metres, upon a bar, not of temperature controlled platinum but ice-cold Tooheys, Redback, Swan, Gage's or whatever is currently on offer at the The Lucky Shag in Barrack St Perth WA over the festive season. (Bring your own cormorant, it's that kind Shag).
Ron Hatch of GPS is correct. If anyone is looking for a better-fit, intellectual honesty, sounder mathematics and accurate cartography the best offer for the nautical mile is 6080.22ft. Which is coincidentally the old Admiralty Mile of Clarke, Bamford, Gauss, Andoyer, Weems and Lambert. But to redefine the nautical mile back more or less to what it was because t'committee goofed and got the form of the earth sized wrong would lead to too many red faces rather than Two Too many Toohey's.
Jeppesens are proud of their accuracy drawn to a scale of 1 inch to the old nautical mile. God went one better at twelve inches to the foot. Hatch has surveyed it and says the old boys with their glass and brass made a better fist of it than the bunch of academics in Bermuda. He also positions his satellites with a theory suggestive that Einstein didn't quite get everything right. (See his Ether Gage Theory). And now to raise the temperature of my next stubbie by one degree, how fast must my hand move again?
Festive Chiz
Mr and Mrs "E"
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Old Smokey,
Just being pedantic for a sec.... it's not exponential, but a simple square law.
But yes, it's non-linear, which is the main point.
For me as an engineer, it's still counter-intuitive, that, whether you barrel along at 2000 km/h TAS at sealevel or at 2000 km/h TAS at 60,000 ft, the temperature rise is the same, notwithstanding the far lower air density.
I'm not querying the formulae... worked with them long enough. It's just that it doesn't 'feel' right.
I expect the answer is elementary...
Temperature is a property of each individual molecule.
In a total temperature probe each indivdual molecule is brought to rest, so it experiences the same temperature rise, while the number of molecules does not enter into the equation.
Sounds right....
As a boffin, I now ask myself the question: to what extent does the air density affect the heat transfer, be it to the total temperature sensor, or to the structure.
To take an extreme case, think of the space station, where the total air temp works out at something like 30,000°C, but there are simply not enough air molecules to result in any significant kinetic heating.
CJ
Just being pedantic for a sec.... it's not exponential, but a simple square law.
But yes, it's non-linear, which is the main point.
For me as an engineer, it's still counter-intuitive, that, whether you barrel along at 2000 km/h TAS at sealevel or at 2000 km/h TAS at 60,000 ft, the temperature rise is the same, notwithstanding the far lower air density.
I'm not querying the formulae... worked with them long enough. It's just that it doesn't 'feel' right.
I expect the answer is elementary...
Temperature is a property of each individual molecule.
In a total temperature probe each indivdual molecule is brought to rest, so it experiences the same temperature rise, while the number of molecules does not enter into the equation.
Sounds right....
As a boffin, I now ask myself the question: to what extent does the air density affect the heat transfer, be it to the total temperature sensor, or to the structure.
To take an extreme case, think of the space station, where the total air temp works out at something like 30,000°C, but there are simply not enough air molecules to result in any significant kinetic heating.
CJ
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Originally Posted by Beeline
One of the Concordes still has a hat wedged in it from its final flight! Cant remember which one though!
Alpha Fox at Filton for certain (I've seen it), Alpha Charlie at Birmingham almost certain, Alpha Golf at Seattle (was pulled out by a vandal, but they slid it back). Not sure about Alpha Delta in New York or Alpha Echo in Barbados.
IIRC, at Mach 2 there was a good two inches between the right side of the flight engineer's panel and the bulkhead, and less than hafl an inch on the ground.
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old, not bold,
10 inches is 25.4cm. And thank goodness al the rest behind the .4 is zeros.
If that hadn't been the case I doubt we could ever have gotten all the French and British bits to mate....
Well, there are an awful lot of expansion joints and other tricks of the trade. 
Since you live in the UK, come down to Brooklands Museum in Weybridge sometime, and have a look at the fuselage section inside Delta-Golf that has been left "bare".
Lengthwise the skin IS the frame, the skin panels are machined from solid blocks, so when heated they expand uniformly.
Think of a beer can, or rather a tuna can in view of the proportions.
Top and bottom rim are the transverse frames which give the fuselage its shape and stiffness.
The wall is the skin, stiff enough so you can't crush it.
Now heat your tuna can. It just expands a bit in length and a little bit in diameter. No problem.
Same as Concorde.
And while everybody knows about 'spamcans', I don't think anybody has yet compared Concorde to a batch of tuna cans put end to end.
So I'm getting my tin hat and my coat, and I'm off for Christmas dinner.
Best wishes to everybody.
Christian
With all due deference to you scientists, all I know is that the speed-induced temperature rise was enough to stretch the Concorde by, as I remember it, 10 inches (25.3 or so cm?) at M2.
If that hadn't been the case I doubt we could ever have gotten all the French and British bits to mate....
I was always amazed that the designers predicted it correctly, so that all the wires and pipes and stuff had the right amount of slack.
I've never quite understood how the skin stretched with the frame, but no doubt someone can help with that.
Lengthwise the skin IS the frame, the skin panels are machined from solid blocks, so when heated they expand uniformly.
Think of a beer can, or rather a tuna can in view of the proportions.
Top and bottom rim are the transverse frames which give the fuselage its shape and stiffness.
The wall is the skin, stiff enough so you can't crush it.
Now heat your tuna can. It just expands a bit in length and a little bit in diameter. No problem.
Same as Concorde.
And while everybody knows about 'spamcans', I don't think anybody has yet compared Concorde to a batch of tuna cans put end to end.
So I'm getting my tin hat and my coat, and I'm off for Christmas dinner.
Best wishes to everybody.
Christian
