Once upon a time, Jeffrey Kaplan   said:   
   >If something goes wrong, you're screwed either way.  Heat shields can   
   >fail, parachutes can fail in several ways, etc.   
      
   Wings give you a much larger area of failure.  You are also having to   
   launch a lot more structure, which is wasted mass to orbit.   
      
   >> We are a long way from any technology that would allow a vehicle to take   
   >> off like an airplane and make it to space.   
   >   
   >That is merely a question of engineering, not science.  We HAVE the   
   >technology, just not the will due to cost.  I'd bet that any of us here   
   >could sketch out the basic design criteria of such a craft and with the   
   >proper engineering to make it real, it would work.  It might cost a   
   >couple billion dollars at first and be the size of a 747 or C5, but it   
   >would work.   
      
   Go ahead, I'll wait.  How is it looking?   
      
   We really don't have the technology to do that.  We really can't make   
   the vehicle much lighter (and still be able to carry anything) due to   
   the limits of materials.  For example, the X-33 test vehicle was going   
   to use carbon-fiber composite fuel tanks, but they didn't work out.   
   Liquid hydrogen is a hard thing to hold; it blew the sides off of the   
   tank in a test.  The SSME (Space Shuttle Main Engine) is already the   
   highest performing rocket engine ever built, and it can't come anywhere   
   near handling a horizontal takeoff.   
      
   The rail-gun type launch system _might_ make this feasible, but we don't   
   know how to actually build that either (and again, the problems are not   
   simply money).   
      
   The amount of energy required to get to low Earth orbit is massive when   
   compared with air flight.  The top speed of a 747 is 567 mph; Shuttle   
   orbital velocity is about 17,500 mph.   
      
   I'd be suprised if you could build something the size of a 747 or a C5,   
   takeoff horizontally, and get it to space, no matter how much money you   
   spent.   
      
   Besides, "just throw money at it" doesn't really make much sense.  If   
   you can spend a fraction of the price on a one- (or few-) use capsule   
   and a throw-away rocket, why spend much much more on the magic   
   spaceplane, other than to fulfill science-fiction dreams?   
      
   >> The only significant advantage to the Shuttle was that it could return   
   >> large payloads from space, but that turned out to be an expensive   
   >> option.   
   >   
   >I just think that NASA is taking a giant step backwards with their   
   >current plans on the eventual replacement of the Shuttle.  We SHOULD be   
   >using self-contained and fully reusable spaceplanes by now to get to   
   >and from orbit.   
      
   That kind of thinking got us the Shuttle, which really proved that even   
   vertical takeoff and horizontal landing wasn't that great of an idea.   
   You might could improve on the safety by having a first stage entirely   
   below the vehicle, but you'd end up with an impossibly tall stack.   
      
   Reusable didn't work out that well either.  The stresses on the vehicle   
   were pushing the limits, so a lot of inspection and refurbishment was   
   required between every flight (the SSMEs were essentially rebuilt every   
   time).   
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   Chris Adams    
   Systems and Network Administrator - HiWAAY Internet Services   
   I don't speak for anybody but myself - that's enough trouble.   
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