(149d) On Stability, Dynamics of Lunar Oxygen Production From Ilmenite in a 0.167 G Fluidized Bed

Ilmenite (FeTiO₃) can be found in the lunar crust, in beach sands in Canada, USA and Australia.  Oxygen can be generated from these rocks for use in lunar missions and lunar colonization by reduction reactions.  Other materials sucah as CaAl₂Si₂O₈ may also be considered (Caroll, 1983). Both ilmenite and anorhite  are lunar-surface-minable, occurs in soils, breccias, rocks and basalts. Hydrogen appears as both reactant and product in the electrolytic reactions. This can be modelled usind the Reactions in Circle scheme (Sharma, 2010).  For certain values of reaction rate constants subcritical damped oscillations in concentration of Oxygen can be expected.  These can be performed in a 0.167G lunar fluidized bed. The bubbling bed model is revisited in light of the microgravity considerations.  Transient dynamics of the ilmenite reductions reactions in a CSTR were evaluated.  The system was found to be stable for small values of Damkohler numbers for forward reduction reaction, reverse reaction and electrloytic split of water reactions. For larger values of Damkohler numbers such that (-1 + Da₂ + Da_b + Da_f) > 0 one of the species concentration would be stable and the other would be unstable. When the "b²-4ac" in the quadratic auxilliary equation is a perfect square, oscillations will not arise. Studies of transient dynamics in a PFR were undertaken.  The resulting equation in dimensionless form was found to be of the hyperbolic PDE of the second order. The solution was obtained using the method of separation of variables.  Significance of wave form of solutions are discussed. Incentives for lunar oxygen production from lunar materials as opposed to supplying it from earth have been outlined in Criswell (1983) and Davis (1983).  Thermodynamic and scale-up considerations are discussed.

Background

 Scientific and industrial projects on the moon is less science fiction and more a real possibility.  A small batch of concrete was synthesized using 1.4 ounces of lunar soil provided by NASA at Stokie, IL by Construction Technology Labs Inc.  Side by side comparisons on compressive strength,  static  and dynamic modulus of elasticity, Poisson's ratio at peak load, modulus of rupture and coefficient of thermal expansion between concrete made with lunar soil and that made with earth soild was performed.  The properties of the specimen prepared with lunar soil were found to be as good as the one prepared with earth's soil.  Water is not available in abundance in moon despite the reports from Chandrayan (2009).  Moon Minearlogy Mapper, M³ on Chandrayan-1 has detected water on the moon.  M³ detected absorption features near 2.8 - 3.0 μm on the surface of the moon.  Retention of OH and H₂O is an ongoing surficial process. Water can be created by heating ilmenite with hydrogen.   The normal boiling point of liquid hydrogen is -252.8 ⁰C.  Concrete is more suitable for lunar construction compared with other materials.  Production of concrete requires only 1.3% of energy needed to make steel.  This may reflect in cost savings.  Minimal loss of concrete strength at lunar temperatures that vary between -250 F to + 250 F facing the sun.   Cement can make excellent gamma ray absorbing materials. Concrete is also abrasion resistant besides.