From: henry@spsystems.net   
      
   In article <45022fc8.0407151347.45b6a20d@posting.google.com>,   
   Iain McClatchie  wrote:   
   >Henry> Unfortunately, it tends to need a lot of gas, and this limits benefits.   
   >   
   >References?   
      
   Check the Hagemann et al survey paper on advanced nozzles in the Sept/Oct   
   1998 issue of Journal of Propulsion & Power -- he mentioned Aerojet tests   
   of the idea, and he may have supplied a reference.   
      
   >Has anyone done solid nozzle inserts that get ejected at altitude?   
      
   Nobody's flown it, but lots of people have thought about it.  The J-2   
   ground testing used a water-cooled fixed insert for some tests, and an   
   RD-0120 has been fired with a nozzle insert that provided a complete   
   secondary nozzle (not sure whether they tested ejection, although that   
   was the long-term intent).  Main concerns are the release process:   
   reliability, mechanical and thermal shock loads, symmetry, collision risk.   
   There is also -- as with many other altitude-compensation schemes -- some   
   small performance penalty at sea level, due to suboptimal nozzle contours   
   and aspiration drag.  (Ref:  same paper.)   
   --   
   "Think outside the box -- the box isn't our friend."    |   Henry Spencer   
                                   -- George Herbert       | henry@spsystems.net   
      
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