On 10/12/2010 5:14 PM, Dan Dassow wrote:   
   >> If you have multiple engine types then you   
   >> have to carry them with you, thus adding weight.   
   >>   
   >> The one thing that might really work well is a rail gun launcher.  It   
   >> probably would not get you supersonic, but it could get you above the   
   >> thickest of the atmosphere and a good speed boost.  It's probably too   
   >> expensive to build in comparison to booster rockets.  Maintenance would   
   >> probably also be a problem.  Just imagine maintaining a, say, 20 mile   
   >> long structure built on the side of a high mountain, throughout the   
   >> winter.  Just keeping it free from snow and ice would be a problem.   
   >> --   
   >> James A. Robbins   
   >> Network Engineer   
   >> The Ohio State University   
   >    
   > http://www.csmonitor.com/Science/Cool-Astronomy/2010/0914/NASA   
   considering-rail-gun-launch-system   
   > NASA considering rail gun launch system   
   > Rail guns, which use a magnetic field to accelerate a mass to high   
   > speeds, are being looked at by NASA as a potential space launch   
   > system.   
   > By Nancy Atkinson, Universe Today / September 14, 2010   
      
   Excellent!  I'm glad they are looking into this.  They also used a great   
   idea in separating the air-breathing stage from the orbital stage, thus   
   saving on weight-to-orbit.   
      
   The biggest problem the article glosses over is the need to bring the   
   launch vehicle up to supersonic velocity by the end of the track.   
   Ram and scram-jet engines do not work below supersonic velocities.   
   Moving an object at supersonic velocities along a fixed track produces   
   lots of problems (as the land speed record vehicles have to contend   
   with), like shock-waves reflected between the bottom of the vehicle   
   and the ground or track. Nothing that cannot be overcome, but a real   
   engineering headache.   
      
   I think they really need to take advantage of existing terrain to get   
   the vehicle above as much atmosphere as possible, but where to do this?   
   The high peaks of the Rockies have protected invironments around them   
   and you don't want the overpressure wave to blow out all the windows in,   
   say, Denver every time you launch.  That's why there are restrictions on   
   flying supersonic over the continental US.  Stuff to think about.   
   --   
   James A. Robbins   
   Network Engineer   
   The Ohio State University   
   --- SBBSecho 2.12-Win32   
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