From: henry@spsystems.net   
      
   In article ,   
   Marc 182   wrote:   
   >> Right, but so long as the requirements are moderate, then increasing   
   >> these specs should simply require more of some components without   
   >> changing the overall design.  It takes little design effort and only   
   >> moderate $$'s to simple have *more* board space, or *more* shielding,   
   >> or *more* overall mass...   
   >   
   >No no no.  I don't design space probes, but it's obvious that this   
   >argument is not correct. You don't get to increase these specs at all,   
   >they are constraints.   
      
   More precisely -- speaking as someone who does sometimes design these   
   things -- you don't get to increase those specs unless you can make a   
   *very* good case that the processor subsystem is uniquely deserving and   
   that the whole mission would benefit from increases there.   
      
   It's very rare that resources, especially mass and power, are abundant.   
   Much more common is to have strict upper limits set by outside constraints   
   (e.g., launcher payload capacity) and basic design (e.g., solar-array   
   area), and to be under considerable pressure to get as much as possible   
   out of them, or to accomplish a mission that only barely fits.  That being   
   the case, any extra allocated to one subsystem has to come out of another.   
      
   In this environment, bloatware is not acceptable.  Reasonably efficient   
   use of resources is mandatory, even if it takes somewhat more effort.   
   Although the precise tradeoff depends on the funding environment, usually   
   it is easier to add some more development effort than to argue with the   
   resource constraints.   
      
   >...A bigger launcher? Now you're talking millions   
   >more to launch a bloated spacecraft...   
      
   This is one issue where compromises are sometimes preferable.  It does   
   sometimes happen that a spacecraft which would be a very tight fit on   
   (say) a Delta II launch will see an overall project cost saving by moving   
   up to (say) an Atlas, because the easier engineering saves enough to pay   
   for the difference in launch cost.  But it can be politically difficult to   
   negotiate such a change even if the numbers look favorable.   
   --   
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   since Oct; first surprises seen; papers pending.        | henry@spsystems.net   
      
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