From: junkmail@wolfkeeper.plus.com   
      
   Iain McClatchie wrote:   
   > If you want to do parallel staging, you need a way to make your upper stage   
   > nozzle (a) survive the first 40 seconds of flight and (b) not throw your   
   > thrust vector around randomly.  If you add gas from the boosters' tanks,   
   > you might be able to dump most of the weight of the system with the   
   > boosters once you don't need it anymore.  The downside is that you will   
   > be carrying it for twice as long as you actually need it.   
      
   Allegedly, another way to do this is to use the ambient air- holes   
   around the nozzle at the appropriate place/angle can apparently trigger   
   separation.   
      
   As the rocket climbs, the ambient pressure reduces and the nozzle fills.   
      
   Of course you don't want the hot gas to go backwards through the holes,   
   but pretty much, with careful design, it won't- it's very difficult for   
   hypersonic gas to suddenly reverse direction.   
      
   > Has anyone done solid nozzle inserts that get ejected at altitude?   
      
   That one's described in Sutton.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)