XPost: sci.astro, sci.physics, sci.space.policy   
   From: jfindley@cinci.nospam.rr.com   
      
   In article , droleary@   
   2017usenet1.subsume.com says...   
   > For your reference, records indicate that   
   > Jeff Findley  wrote:   
   >   
   > > High altitude balloon launch is a tad risky and only gains you a bit of   
   > > altitude and zero velocity.  Not worth the complexity and cost, IMHO.   
   >   
   > Like I said, it might not *currently* be viable, but as an alternative   
   > technology it brings new sets of trade-offs to the table such that a few   
   > tweaks here and there might make it viable for certain kinds of launches   
   > (e.g., ?bulky? items that are hard to make aerodynamically efficient   
   > benefit from starting at the highest possible altitude).   
      
   Balloon launch isn't worth the trades which have to be made, IMHO.   
      
   > > BFR/BFS is planned to be "zero waste" from the very beginning.  Fully   
   > > reusable TSTO with "gas and go" like operations.   
   >   
   > But that?s not the true ?zero waste? I was talking about.  Any resources   
   > that you?re sending up *and* down, along with any fuels you burn to do it   
   > safely, is a waste.  It may be a necessary waste for the current launch   
   > technologies, so it?s good to minimize it, but I still say it?s a good   
   > idea to think about ways to shoot stuff into space that doesn?t involve a   
   > lot of heavy stuff coming back to Earth.   
      
   By your definition, a passenger carrying aircraft is "waste" because it   
   flies from one destination to another while carrying passengers.  But   
   that sort of "waste" is absolutely not a metric to optimize.  Passengers   
   are buying the cheapest ticket for the flight that gets them to their   
   destination.  They don't give a rat's ass about the "waste" of the   
   actual aircraft having to fly there and back.   
      
   Back to space launch.  We're nowhere near the minimum cost per kg   
   payload to orbit with chemical launch vehicles.  Propellant costs are   
   currently less than 1% of launch costs, even for SpaceX.   
      
   Any "waste" of propellant that allows full reuse of hardware is   
   currently worth the investment.  When your hardware costs more than two   
   orders of magnitude more than your propellant does, it makes a hell of a   
   lot of sense to "expend" a bit of propellant to get your expensive   
   hardware back intact.   
      
   When faced with an optimization problem, you look for the biggest "bang   
   for the buck" bits to optimize.  Propellant "waste" is *not* that, not   
   by a couple orders of magnitude.  Also, your launch hardware is a   
   precious commodity, so it makes all the sense in the world to recover it   
   and use it multiple times, just like a passenger carrying jet aircraft.   
      
   Jeff   
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