Previously on rec.arts.sf.tv.babylon5.moderated, Chris Adams said:   
      
   > >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?   
      
   I'm not an engineer, I never claimed to be.  I can't build the thing.   
      
   > 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.   
      
   That's why it would have multiple engine types.  From what little I do   
   know, I understand that rockets are not the most efficient for   
   in-atmosphere use.  Ideally, it would have three sets of engines, each   
   for a different stage of the flight:   
      
   1: Jets for lower atmosphere flight   
   2: RAM or SCRAM Jets for upper atmosphere flight   
   3: Rockets for use in the vacuum   
      
   If the three sets turns out to be not feasible, then scrap the second   
   set and use just jets and rockets.   
      
   > 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.   
      
   Use jet engines for horizontal lift-off and flight up to the upper   
   atmosphere, and then light off the rockets for the push into orbit.   
      
   Or, if you are really strapped for weight, then make it a dual-stage   
   craft, which I believe is the direction Virgin Galactic is going: a jet   
   powered atmospheric flight first stage with the orbiter second stage   
   piggy-backing.  First stage returns under power to the launch site and   
   the orbiter continues up under rocket power, and later returns on a   
   glide path.   
      
   > 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?   
      
   Because it is, or can be, bigger.  Economics of scale, etc.  Sure, a   
   747 costs lots more than a Piper Cub, but the 747 can carry   
   significantly more.  Assuming a full load, this makes the per-pound   
   lift more economical and thus more viable.   
      
   The spaceplane concept would allow for larger scale commercial use of   
   and travel to/from orbit.   
      
   > >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).   
      
   Yeah, the turn-around time was supposed to be a couple of weeks, not   
   months.   
      
   As I recall, there was a hell of a lot of changes made to the original   
   shuttle design because NASA was in a rush and didn't want to wait for   
   what was originally planned, which was supposed to be better than what   
   we eventually got.  Just because we got a bad version doesn't mean that   
   the concept is bad, it just means that we got a bad implementation of   
   the concept.   
      
   --    
   Jeffrey Kaplan                                         www.gordol.org   
   Double ROT13 encoded for your protection   
      
   "On the other hand, maybe wounding him isn't such a bad idea after   
   all."  (Dr. Franklin, B5 "Dust To Dust")   
   --- SBBSecho 2.12-Win32   
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