From: hrubin@stat.purdue.edu   
      
   In article <44DF4159.609952FE@nospam.com>,   
   Andrew Nowicki   wrote:   
   >dan wrote:   
      
   >> Back in the 50's when no one knew if spaceflight was even possible,   
   >> several tests were made with sounding rockets launched by balloon at   
   >> high altitude.  However the payload capability of even very large   
   >> balloons declines at extreme altitude, and launching a large balloon is   
   >> tricky. Because of the long period climbing to launch altitude   
   >> cryogenic propellants were not practical. Ultimately it was not   
   >> possible to carry rockets capable of getting into orbit. A similar   
   >> problem will occur with rotorcraft.   
      
   >It will not.   
      
   >The helicopter can fly much faster than the balloon.   
   >If it flies vertically at the rate of 33 meters per second,   
   >it will reach the altitude of 30 kilometers in 15 minutes.   
   >Liquid oxygen and liquid methane will not evaporate   
   >in 15 minutes.   
      
   I question whether that rate can be maintained at   
   high altitudes.  Both an airplane and a helicopter   
   rely on air (or some other gas) for there to be   
   any power usable for lifting.   
      
   >> On the other hand, a fixed-wing aircraft.i.e. the B-70, can indeed be   
   >> designed to carry a large payload at high altitude. While a large blunt   
   >> cone would have to much drag for external carriage on an aircraft, a   
   >> saucer-shaped vehicle could be carried and launched edge first and   
   >> re-enter flat side first; this is pretty much what Rutan's SpaceShip   
   >> One does with its pivoting tail. This can spread the heating over a   
   >> large area as with the Apollo Capsule, reducing thermal loads.   
      
   >The airplane is superior to rocket as a means of transportation   
   >through the troposphere because it is slower and much more   
   >reusable. It is however not as slow as the helicopter, and   
   >the separation of the rocket launcher and its cargo from the   
   >airplane is tricky due to the aerodynamic drag.   
      
   If it can reach 30 kilometers, the drag will be small.   
      
      
      
      
      
   --   
   This address is for information only.  I do not claim that these views   
   are those of the Statistics Department or of Purdue University.   
   Herman Rubin, Department of Statistics, Purdue University   
   hrubin@stat.purdue.edu         Phone: (765)494-6054   FAX: (765)494-0558   
      
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