From: root@127.0.0.1.retro.com   
      
   > > There's a lot of traffic in this thread about powering the climber. Why   
   > > can't it simply have a diesel/gasoline engine with its own oxygen   
   > > supply?   
      
   just possibly something to this...   
      
   > > Or run electrical cables up the elevator to power an electric motor?   
      
   But this was a bad idea.   
      
   > > Why make things more complicated than they need to be?   
   >   
   > Your proposal is not _totally_ implausible. The energy required to climb   
   > a beanstalk is only a small fraction of the energy required to accelerate   
   > a payload into Low Earth Orbit; the fuel and oxygen tankage required   
   > would be large, but not prohibitively so.   
      
   I did a quick calculation assume modern diesels assuming a 10 tonne payload   
   starting with 10 tonnes of fuel. From my matlab script:   
      
   G=6.67300e-11; %gravitional constant   
   Mc=10e3;           %Mass of cargo, 10tonnes   
   Me=5.95e24;      %mass of earth   
   e=0.5;                 %efficiency of typical 4 stroke   
   Esp=40e6;          %fuel energy per kg (assume air breathing)   
   r0=12760e3/2;   %start point (radius of earth)   
   Mf=10e3;           %mass of fuel   
      
   Equating the energy required to get out of the gravity well to the energy   
   available in the fuel tank:   
   GMe(Mf+Mc)(1/r0-1/r1) = e Esp Mf   
      
   This makes three assumptions, One is that we're air-breathing all the way,   
   which might not be too unreasonable because the hardest part (where g is   
   highest and the engine will be working its hardest) has plenty of air. Even   
   at high altititudes a super-charger or similar technology could be applied   
   to allow the engine to breath the air, only switching to a liquid oxygen   
   tank, or oxygen-less fuel when truely in space.   
   The second is that the mass of the fuel in the tank remains constant -   
   obviously it would be used up.   
   The third is that the 10tonnes of payload would of course include the heavy   
   engine.   
      
   I get from this about 1000km of altitude - only about 1/30th of the altitude   
   needed. So perhaps not entirely unreasonable, but difficult nonetheless.   
      
      
   Rest of matlab script:   
      
   r1=1/(1/r0 - (Esp*e*Mf)/(G*Me*(Mf+Mc))); %calculate height   
      
   altitude=(r1-r0)/1e6     %million meters (need about 30e6)   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)