From: henry@spsystems.net   
      
   In article <1109683457.045605.47970@z14g2000cwz.googlegroups.com>,   
   Cray74@gmail.com  wrote:   
   >Is it possible for an upper stage to get to low Earth orbit with less   
   >than 1G of acceleration (without using aerodynamic lift)?   
      
   There's nothing fundamentally impossible about it.  Saturn V launches   
   averaged less than 1.5G during the S-II/S-IVB burns to orbit.   
      
   The only real impact of lower acceleration is that reaching orbit takes   
   longer, meaning that your first stage has to supply more of an upward kick   
   to keep the upper stages out of the atmosphere long enough.  Centrifugal   
   lift goes as velocity squared, which means it doesn't become important   
   until you're near orbital velocity.  Until then, with no aerodynamic lift,   
   little centrifugal lift, and little thrust lift (at low acceleration, even   
   pointing the engines quite sharply down won't help much), all that keeps   
   you out of the atmosphere is that initial upward momentum supplied by the   
   first stage.  So there's got to be more of it, and the first stage is   
   probably going to take higher gravity losses supplying it.   
      
   So yes, it's possible, but you do pay a price.  It's less efficient than   
   having more thrust.   
   --   
   "Think outside the box -- the box isn't our friend."    |   Henry Spencer   
                                   -- George Herbert       | henry@spsystems.net   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)