From: henry@spsystems.net   
      
   In article <3ffb1675.2373790@news.dsl.pipex.com>,   
   Christopher  wrote:   
   >If the suit is going to be a polymer body hugging soft suit then it is   
   >a reasonably simple exercise as the astronaut will put it on like a   
   >heavy duty body stocking feet first...   
      
   If you're thinking of the Space Activity Suit, no, putting it on is not   
   particularly simple, because it's necessarily a very tight fit.   
      
   >but all the paintings and NASA   
   >illustrations I've seen show the Mars suit to be a full pressure suit.   
      
   That's the orthodox party line.  Left undiscussed is the question of how   
   a classical suit can be made light enough for sustained wear on Mars.   
   (Even the Apollo suits would probably be too heavy.)   
      
   (NB, all suits even vaguely appropriate for use on Mars are full pressure   
   suits -- that is a technical term with a specific meaning.)   
      
   >The Apollo eva suits had IIRC a series of zippers, and Neil, Buzz and   
   >the other guys entered the suit from the front, but they were one time   
   >suits, and zippers are not very airtight.   
      
   Zippers can be adequately airtight, and those suits were reusable a fair   
   number of times, in the absence of lunar dust.  (Their expected working   
   life in the presence of lunar dust was short -- joints, visors, etc. were   
   giving trouble at the end of the 3-day stays of the later Apollos.)   
      
   >The Russians have an eva suit where the entry is via the back with a   
   >door like arrangement, but that to is problematical...   
      
   Actually it's generally considered a superior design.  A new US suit for   
   shuttle/station use would almost certainly work the same way.   
      
   >...as it requires someone else to swing the entry door closed...   
      
   With *any* current suit design, a helper is very useful.   
      
   >I would have a Oxygen Nitrogen mix at 12lb psi so no prebreathing is   
   >required, as in an emergancy the suit would need to be put on asap.   
      
   NASA and the Russians would both *love* to have a no-prebreathing suit.   
   It isn't sheer stupidity that has prevented this.  Nobody has been able to   
   make a classical fabric suit whose limbs are adequately flexible with that   
   much pressure inside them.   
      
   None of these suits is something you can put on quickly.  Emergencies have   
   to be handled otherwise.   
   --   
   MOST launched 30 June; science observations running     |   Henry Spencer   
   since Oct; first surprises seen; papers pending.        | henry@spsystems.net   
      
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