From: schillin@spock.usc.edu   
      
   "Allen Thomson"  writes:   
      
   >John Schilling wrote:   
   >> "Allen Thomson"  writes:   
      
   >> >I checked on MREs and the Army's nutrition lab says that they're   
   >> >nutritionally good beyond 10 years if held unfrozen at 15 C   
   >> >(60 degrees 'murkin).  So I agree, the claim that a few-year   
   >> >mission couldn't get along on preserved food plus some   
   >> >supplements looks pretty odd.   
      
   >> The Army's nutrition lab also says that MREs, new or old, are   
   >> nutritionally *bad* if they are the entirety of one's diet for   
   >> more than a few weeks.  If you believe the Army, you can't just   
   >> stock your Mars ship with a three-year supply of MREs and imagine   
   >> the problem has been solved.   
      
   >Er, I used the MREs as an example of the preservability of food   
   >while retaining whatever nutritional virtue it started out   
   >with. In the case of MREs, that virtue seems to be considerable,   
   >if not long-term adequate.   
      
   Right.  The issue isn't "retaining whatever nutritional virtue   
   it started out with"; a hermetically sealed container of pure   
   cane sugar will do that.  Lots of foods, we know how to store   
   more or less indefinitely.   
      
   The issue is whether a long-term adequate diet can be constructed   
   exclusively from storable foods.  The answer is probably yes, but   
   not yet AFIK *proven* to be yes.   
      
      
   >However, the viewgraph that started this seemed to say that   
   >the state of the art isn't here for preserving nutritionally   
   >adequate food for multi-year Mars missions.  So is there some   
   >ingredient of a multi-year nutritionally complete diet that   
   >can't be preserved by chilling or freezing or dehydration or   
   >whatever?  If so, what might it be?   
      
   Don't know; I can't find the original references at my local   
   library or online, just abstracts and summaries.  What I can   
   find suggests it isn't anything as simple as a missing vitamin   
   or amino acid or whatnot.  But in the course of developing the   
   MRE, the Army did *something* to the mix that resulted in a   
   food that would last indefinitely if kept cold, but will lead   
   to unexplained weight loss and mental deterioration if used   
   exclusively for more than a few weeks.   
      
   If it were trivial to produce a ration that could be stored   
   indefinitely and consumed exclusively, I would assume that   
   the Army would have done so in developing the MRE.  It would   
   certainly have been a useful enough combination to be worth   
   a little bit of extra effort.   
      
   So I take the MRE, and similar rations, as evidence that it is   
   not trivial to produce rations suitable for long-term space   
   flight.  I don't expect it to be hugely difficult either; like   
   the zero-gravity toilet it's just one of those things that has   
   to be done and will be done but isn't quite as easy as it sounds   
   like it should be.   
      
      
   At very least, three or four years before the first manned Mars   
   mission we ought to take our best guess and put it to the test.   
   Round up a batch of graduate students or other suitable guinea   
   pigs, give them the locker or freezer full of astro-MREs, and   
   say "This is all you get to eat for the next three years.  Let   
   us know how it works out..."   
      
      
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   *John Schilling                    * "Anything worth doing,         *   
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