XPost: sci.space.shuttle   
   From: alcore@uurth.com   
      
   On 28 Jul 2005 khatcat@hotmail.com wrote:   
      
   >I think I understand why objects heat up when going through the   
   >atmosphere and therefore why re-entry vehicles need heat shielding.  My   
   >question is why we don't need heat shielding when launching.  Aren't we   
   >going through the same atmosphere?   
      
   At takeoff, a lot of fuel is burned to climb (more or less) straight up.   
   Only *after* altitude (above the air, more or less) is reached does the   
   vehicle pitch over and use it's remaining fuel to gain orbital speed.   
      
   These are not exclusive moves with nice square angles, mind you.  It's a   
   slow curve, with more and more horizontal drive the higher up you go.   
      
   Yes, the Shuttle would burn up on takeoff if it had more than a tiny   
   fraction of orbital speed near the ground.  But it doesn't get to that   
   speed until it's already gotten almost all of the required altitude.   
      
   Since there's no fuel left to shed all that velocity, the only way to get   
   rid of it is to dip down into the atmosphere...  And all of the energy   
   stored as speed is turned into friction heat...   
      
   Gene P.   
   Slidell, LA   
      
   --   
   Alcore Nilth - The Mad Alchemist of Gevbeck   
   alcore@uurth.com   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)