From: derek_c@cix.co.uk   
      
   > *From:* "Ian Woollard"    
   > *Date:* Wed, 15 Mar 2006 19:42:39 -0000   
   >   
   > mike Williamson wrote:   
   > > Wings do not allow for less energy to be used to orbit a craft-   
   > > while   
   > > they provide lift they do not provide any energy.  In fact, since   
   > > they   
   > > also generate drag, a winged vehicle would almost certainly require   
   > > more fuel to reach orbit, since the tubular design will have less   
   > > drag to overcome.   
   >   
   > Careful here. Wings do indeed save energy; this is because wings have   
   > a   
   > lift/drag ratio, the drag is approximately equal to the engine thrust,   
   > and so thrust can be reduced- reducing the propellant needed to carry   
   > the vehicle whilst within the atmosphere.   
   >   
   > The root cause of the energy saving is that the vehicle uses wing to   
   > throw air downwards relatively slowly; the slow speed represents lower   
   > energy needed to carry the vehicle; the high exhaust speed of rocket   
   > engines uses more energy (since energy goes as a square law on the   
   > exhaust velocity), although it saves propellant mass.   
   >   
   > Even with Apollo, studies showed that a lifting approach did indeed   
   > increase payload (although the payload increase was very marginal.)   
   >   
   > The big downside of wings is after you leave the atmosphere- wings   
   > push   
   > up dry mass, and then it is very easy to lose everything that was   
   > gained during ascent and then some; a good mass ratio is essential   
   > particularly toward the end of the burn.   
   >   
   > > Mike   
      
   So the obvious approach is a two-stage one - fly the wings and   
   atmospheric engines away once they no longer serve a good purpose.   
      
   Spaceship One on steroids...   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)