XPost: rec.arts.sf.written, sci.space.policy, sci.physics   
   From: rgregoryclark@gmSPAMBLOCKail.com   
      
   +++++++++++++++++++++++++++++++++++++++   
   "Fred J. McCall"  wrote in message   
   news:mvtngd1lfatmpo1v3n018v7tdkqftd40u8@4ax.com...   
      
   "Robert Clark"  wrote on Mon, 28 May   
   2018 07:19:51 -0400:   
      
   >   
   >With altitude compensation, allowing even first stage nozzles to achieve   
   >the   
   >highest possible vacuum Isp, and using also  lightweight structures such as   
   >composite tanks, the payload fraction of an SSTO can be comparable to that   
   >of multi-stage rockets, ca. 3%.   
   >   
      
   Sorry, but that doesn't follow.  If you can build an SSTO using those   
   technologies you can also build a multi-stage rocket using the same   
   technologies.  The multi-stage rocket will always do better.   
   +++++++++++++++++++++++++++++++++++++++++++   
      
   You are correct the payload for the multistage rocket will also be improved,   
   which is why I say altitude compensation has an importance beyond its use   
   just for SSTO's.   
      
   However, it turns out the increase for the multi-stage case is in the range   
   of 25%, still a useful increase, but the increase for the single stage case   
   can be 2 to 3 times more with alt. comp.(!)   
      
   The reason why the increase for the multi-stage case is not as dramatic is   
   that a large portion of the flight to orbit is taken up by the upper stages   
   which already will be using vacuum optimized nozzles anyway. But for the   
   SSTO, that one nozzle has to work also for the portions of the flight that   
   otherwise would be using vacuum optimized nozzles, resulting in significant   
   reduction in efficiency without alt.comp.   
      
   So the SSTO will have multiple times more payload with alt. comp., while the   
   multi-stage about 25% more. Then when you consider the singles stage does   
   not have the expense of the upper stage, the per kilo cost can still be   
   comparable.   
      
     Bob Clark   
      
      
   ------------------------------------------------------------------   
   Single-stage-to-orbit was already shown possible 50 years ago   
   with the Titan II first stage.   
   In fact, contrary to popular belief SSTO's are actually easy.   
   Just use the most efficient engines and stages at the same time,   
   and the result will automatically be SSTO.   
   Blog: Http://Exoscientist.blogspot.com   
   ------------------------------------------------------------------   
      
   --   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)