From: alain245@videotron.ca   
      
   On Oct/16/2021 at 04:12, JF Mezei wrote :   
   > On 2021-10-15 20:23, Snidely wrote:   
   >   
   >> And bigger wings mean more drag, which means more heating.  Does drag   
   >> got up as V-squared?  Is the Concorde made out of vanadium?   
   >   
   >   
   > My question pertains exactly to this.   
   >   
   > If plane supports the heat at Mach 2 at 60,000feet,  would it sustain   
   > the same heat if it climbed to say 80,000 and accelerated so that wings   
   > would produce equal amount of lift as it did at Mach 2 at 60,000 ?   
   >   
   > If the wings generate the same amount of lift, wouldn't that mean equal   
   > amount of drag and thus heating?   
   >   
   > Again, I am not asking about accelerating the Concorde to a gazillion   
   > kmh or mach 10. Wondering if you exclude engine limitations, you could   
   > make it climb much higher and go at higher speed to match the   
   > lift/drag/heating it got at Mach 2 at 60,000.   
      
   If I recall correctly, heating goes up with speed to the power three.   
   The energy of a collision with a molecule of air goes up with the square   
   of the speed. But since you hit twice as much air when you go twice the   
   speed you get the power three, two for the energy per molecule hit and   
   one for the amount of molecules you hit. Again, if I recall correctly,   
   lift is only proportional to the square of the speed. In both cases,   
   heating and lift are proportional to air density. So as you go faster,   
   you can go higher (lower air density) and still have the same lift, but   
   you have more heating. Or you could go much higher and have the same   
   heating, but then you lose some lift, so you can't do that very much.   
      
   So the answer to your question is no, you can't keep the same heating   
   and lift by going higher.   
      
   In your example with mach 2 at 60,000 feet. If you go to 80,000 feet,   
   you have roughly half the air pressure you had at 60,000 feet, so you   
   would need to go at roughly mach 2*sqrt(2) to have the same lift. But   
   then your heat load would increase by sqrt(2). The heat load being   
   multiplied by sqrt(2) to the power three because of higher speed and   
   divided by 2 because of lower air pressure. This is only a rough   
   approximation, according to the shape of the plane you can have   
   different effect sizes, but as a first approximation this should give   
   you an idea of what is going on.   
      
      
   Alain Fournier   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)