XPost: rec.arts.sf.written, sci.space.policy, sci.physics   
   From: fjmccall@gmail.com   
      
   Greg Goss  wrote on Sun, 17 Jun 2018 19:29:22 -0600:   
      
   >Jeff Findley  wrote:   
   >   
   >>In article ,   
   >>rgregoryclark@gmSPAMBLOCKail.com says...   
   >>> The reason why it?s so high for the TSTO is that the first stage has to do   
   a   
   >>> boost back maneuver to return to the launch site. But for the SSTO you just   
   >>> let the Earth rotate beneath you until you are over the landing site then   
   >>> land vertically.   
   >>>   
   >>   
   >>Don't forget Falcon 9 first stages also do a reentry burn to reduce the   
   >>velocity before hitting the atmosphere.  On a reusable SSTO version of   
   >>the same, you'll either need to reserve a *hell of a lot* of propellant   
   >>for that burn or you'll really need to beef up the TPS.   
   >   
   >I was told that since the first stage is almost all fuel by weight, by   
   >the time you've been dumped from the payload, you hardly weigh   
   >anything.  So the boostback is very cheap in fuel.   
   >   
      
   I wouldn't say "very cheap".  Figures I've seen indicate you need to   
   reserve 10%-15% of fuel to recover the stage.  A Falcon 9 that   
   recovers the first stage only has about 2/3 of the payload of a Falcon   
   9 that is expended.   
      
      
   --   
   "The reasonable man adapts himself to the world; the unreasonable   
    man persists in trying to adapt the world to himself. Therefore,   
    all progress depends on the unreasonable man."   
                                         --George Bernard Shaw   
      
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