From: gdpusch@NO.xnet.SPAM.com   
      
   schillin@spock.usc.edu (John Schilling) writes:   
      
   > "Wim Dekker"  writes:   
   >   
   >> "Mike Miller"  wrote in message   
   >> news:5dcb47db.0309260349.711f770@posting.google.com...   
   >>> DP  wrote in message   
   >> news:<3f6e2897$1@nntp.unige.ch>...   
   >   
   >>> That's a bit different than Jovian atmosphere re-entry. Like,   
   >>> a lot slower. Cassini's RTGs were expected to (IIRC) burn off   
   >>> 33% of their mass if Cassini hit Earth during its sling shots   
   >>> past Earth. Cassini swung by Earth at 19km/s. Galileo hit Jupiter   
   >>> at 48km/s. 2.5 times the entry velocity translates into 6.25   
   >>> times the kinetic energy to be converted into heat per kilogram   
   >>> of spacecraft.   
   >   
   >> I don't understand why kinetic energy increases quadratically   
   >> with speed while the energy it costs to increase speed itself   
   >> seams to be directly proportional to the speed. After all,   
   >> speed = acceleration * time. What's wrong with my reasoning?   
   >   
   > The implicit assumption that acceleration is proportional to   
   > energy or power.  In fact, power = acceleration * velocity,   
      
   Um, I'm sure it's just a typographical omission, but that should read:   
      
       power = mass * acceleration . velocity.   
      
   (from Power = F.v). Which is why:   
      
   > when you do the integral you do get energy = 1/2 * mass * velocity^2.   
      
      
   -- Gordon D. Pusch   
      
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