From: j.garry@chem.leidenuniv.nl   
      
   "Keith Lynch" wrote in message news:bu2hc6$sgs$1@panix1.panix.com...   
      
   > Yes and no.  Pioneers 10 and 11, if I recall correctly, had things   
   > like venetian blinds which opened or closed depending on temperature.   
   > I believe they used no electronics, but just bimetallic strips.   
      
   Indeed - thermal control louvres. Wonderful gizmos, and used in both US and   
   USSR missions for many years.   
      
   > Something like that ought to work even better on Mars than in vacuum.   
      
   Ah, no.   
   Or at least, not in the way intended. Louvres alter the emissivity/albedo   
   ratio of an object, and if that object is lit by sunlight and is in hard   
   vacuum, then altering that ratio radically changes the heat-balance of the   
   object, and thus one can control its temperature.   
      
   On Mars, you have this pervasive if rather thin atmosphere which tends to   
   even out the troughs and peaks of temperature that the spacecraft would   
   otherwise experience if it were in a vacuum.   
      
   -James Garry   
   (fighting a cooling problem in a vacuum chamber this very day - and probably   
   resorting to peltier coolers and stout copper rods)   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)