Microwave Extraction of Water for Space Propellant

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Space exploration is EXTREMELY EXPENSIVE. We live in the deep valley of Earth’s gravitational well. Very large rockets are required to put small payloads into space. Launch mass must be reduced to create a sustainable future in space. A large fraction of spacecraft mass is propellant for in-space propulsion. Large reductions in launch mass will come from production of in-space rocket propellant from in-space water. Vast quantities of water are present at the lunar poles, on Mars, comets, and some asteroids. Using the in-space resource, solar energy, in-space water can be split into hydrogen and oxygen for propellant. Molecular water can even be used for the reaction mass ejecta with ion engines for missions to Mars and beyond. Returning from the surface of Mars will REQUIRE in-situ production of propellant. A manned Mars mission might need ~200 tons of propellant. With Earth launch costs of ~$10,000 per pound, space produced propellant could save billions of dollars that could be used to bootstrap the development of water extraction and rocket propellant production. This would go far to help develop the “cis-Lunar Space” architecture, ”The Transcontinental Railroad” of the 21st century.

We have been developing methods for microwave heating and water extraction for several years. Microwaves will penetrate the low thermal conductivity permafrost regolith to sublime subsurface water ice with subsequent recondensation of the water in an external cold trap. This simple vapor transport process could eliminate the need to excavate the soil and reduce the complexity of surface operations. But most importantly, it could greatly reduce the mass of mining equipment to be transported to the surface of the moon and to other planetary bodies.

Microwave extraction laboratory experiments and numerical simulations over the past 7 years demonstrate the utility of these innovative processes. FEM Multiphysics numerical analysis is being used to model laboratory experiments as well as to simulate possible space experiment scenarios of microwave heating of lunar, Martian, and asteroidal regolith. Different scientific experiments and mining scenarios have been simulated for different frequencies, power, heating times, water concentrations, and for regolith with different dielectric properties. Numerical simulations of energy beamed at the surface as well as delivery of energy down bore holes illustrate possible ways to determine spatial water concentration and subsequent mining operations. Simulations at high frequencies and low power demonstrate possible volatiles science experiments with decomposition of compounds at high temperatures to release chemically bound volatiles in asteroids. Ongoing simulation of water sublimation and vapor transport through regolith will permit the estimation of extraction engineering efficiency metrics. Future simulations of the different microwave processes will permit the design of space experiments, recommendations of potential spacecraft hardware requirements, and optimization of water extraction equipment and operations.

In order to create this new future in space, we need a paradigm shift to utilization of in-space resources, especially water, to leverage the sustainable and growing presence in space for scientific exploration, planetary protection, space debris mitigation, satellite servicing, and even space tourism to help “Create The Future” in Space.

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  • Name:
    Edwin Ethridge
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