XPost: sci.space.policy, sci.physics, rec.arts.sf.science   
   From: peter@tsto.co.uk   
      
   On 03/11/15 14:56, Robert Clark wrote:   
   > Two instances were discussed in the film where unmanned cargo ships were   
   > mentioned to send up supplies to extend the time Whatney or the crew of   
   > the Hermes could survive.   
   [...]   
   > BTW, since this is in regards to "The Martian", for you chemistry heads   
   > out there, are there some foods, liquids, or common materials that might   
   > be on the shuttles that could have filtered out the CO2 in air other   
   > than the lithium canisters? For instance perhaps the solubility of CO2   
   > in water is different than in O2 and there could have been a way to   
   > separate out the CO2 from the air that way.   
      
   Lithium (peroxide) canisters do not just absorb carbon dioxide, they   
   also produce oxygen:   
      
   2 Li2O2 + 2 CO2 → 2 Li2CO3 + O2   
      
   ie about half the oxygen previously absorbed and turned into CO2 by the   
   astronauts is given off.   
      
      
      
   One method for getting rid of excess CO2 might be to heat the used   
   lithium canisters using eg a mirror and sunlight, and then reuse the   
   canisters; but lithium carbonate does not decarboxylate easily, it takes   
   about 1300C.   
      
      
   There are several ways to reversibly absorb CO2, including eg the use of   
   zeolites, molecular sieves, activated carbon, the mixed-metal-oxide   
   system used on the Shuttle, or the amine system used in the Space Station.   
      
      
      
      
      
   -- Peter Fairbrother   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)