From: bondage@frontiernet.net   
      
   Jeff Findley wrote:   
   >   
   > "Tom Kalvelage"  wrote in message   
   > news:aa15a454.0408311955.6f3a981e@posting.google.com...   
   > > For simplicity, both stages are VTVL.  The only thing close to new   
   > > engineering is jettisoning or retracting the second stage exhaust   
   > > bells and closing the holes in the heatshield for reentry, then   
   > > opening the holes for the engines to fire through on landing.   
   >   
   > It's been suggested that instead of doing anything fancy like that, you   
   > could just run some LH2 through the engines during re-entry, or even run the   
   > engines at "idle" during re-entry.  Either of these would greatly reduce the   
   > heat load on the engines.   
   >   
   > > The DC-X, Armadillo Aerospace, and the Japanese RVT vehicle have   
   > > demonstrated VTVL.  The Shuttle has holes in it's heatshield that it   
   > > closes and opens (landing gear).   
   >   
   > True, but you've got to be very careful about this.  Failure of any of the   
   > doors to close would result in loss of vehicle if re-entry is attempted.   
   > Furthermore, failure of the doors to open (on landing gear and/or braking   
   > rockets) would also result in a crash upon landing.   
      
      So? All flying machines with retracable gear face these problems   
   already. A 747 has a bad day if its gear won't extend (As did the DC-X,   
   through a failure tore-connect a pressurization line during servicing   
   after the previous flight. An operational ship would've had a back-up.   
   X-ships operate on more of a shoestring.), and even at low Mach numbers,   
   you don't want unintended extension, either. (It's been said here that   
   that's one reason a shuttle can't do a completely automated entry and   
   landing...gear extension isn't left to the computer at all.)   
      
      Reliability. Engineer it in, embrace it. Some things simply *must*   
   work. This is one we know how to do.   
      
   --   
      
      You know what to remove, to reply....   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)