Advanced life support for space exploration: Air revitalization using amine coated single wall carbon nanotubes
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Advanced life support for space exploration: Air revitalization using amine coated single wall carbon nanotubes. Padraig Moloney1, Chad Huffman2, Olga Gorelik2, Pasha Nikolaev2, Sivaram Arepalli2, Ramakumar Allada3, Micah Springer1, Leonard Yowell1, 1 NASA Johnson Space Center, 2101 Nasa Parkway, Houston TX 2 GBTech Inc. 2200 Space Park Dr Suite 400 Houston, TX 77058 3 National Research Council / NASA Johnson Space Center ABSTRACT The challenges posed by long duration human space flight have made regenerable air revitalization a critical technology. Current systems using disposable lithium hydroxide do not address the difficulties presented by long duration missions. Solid amine systems offer the capability to regeneratively adsorb CO2 using an amine—impregnated porous substrate. Desorption of CO2 is then achieved by exposing the system to vacuum or by increasing temperature. However, thermal inefficiencies and system size constraints prevent adoption of regenerable systems on current and future space vehicles. A key challenge is the thermal management of the adsorbing bed. The adsorbing surface increases in temperature which reduces adsorbing efficiency. The removal of CO2 reduces temperature, which in turn produces a loss in regeneration efficiency. These thermal inefficiencies necessitate prohibitively large volumes of traditional solid-amine materials, which do not have optimized surface areas and pore distributions. Single-wall carbon nanotubes (SWCNTs) may provide a means to increase surface area of the amine support and thermal efficiency. Recent work by Cinke et. al. provided a method of functionalizing SWCNTs and increasing the surface area to the order of 1500 m2/g [1]. We will report on the production of free standing, high surface area carbon nanotube structures currently being impregnated with amines. This novel SWCNT/amine approach will be compared with the current state of the art polymer structure-based system and characterized using SEM, TEM, surface area analysis through Brunauer-Emmett-Teller (BET), and also thermogravimetric equilibrium absorption. Results of SWCNT material improvements from processing modifications will also be presented. INTRODUCTION The Space Shuttle and International Space Station currently utilize two types of CO2 removal methods respectively: lithium hydroxide (LiOH) and molecular sieve systems. LiOH canisters need to be manufactured, certified, stowed and returned to earth after each flight [2]. Valuable flight crew time is used replacing canisters twice every 24 hour period. Molecular sieve systems’ main drawback is the necessary high thermal cycling, typically 400-500 degrees F, and the resultant large power costs. Solid amine systems offer a regenerable and more efficient alternative to the LiOH and molecular sieve solutions. These systems use adsorption beds filled with a high surface area support material coated with an amine. CO2 and water are adsorbed when cabin air is passed through the bed. When the bed has reached capacity, the CO2 and water can be dispo
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