Microwave Extraction of Water for Space Propellant

Edwin Ethridge, Ph.D.
NASA (retired),
Huntsville, AL

Space exploration is extremely expensive because very large rockets are required to put small payloads into space. Large reductions in launch mass will come from production of inspace 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 of 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.

Microwaves will penetrate the low thermal conductivity permafrost regolith to sublime subsurface water ice with subsequent re-condensation 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 seven 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 boreholes 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.

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Honorable Mentions

Sensitive, High Resolution Thermal Infrared Imagers Based on Visible Digital Cameras

Marcos Kleinerman, MetriLight, Amherst, MA

Two-dimensional detector arrays of thermal infrared imagers are expensive, especially at medium and high resolutions. Instead of the bolometric arrays of present thermal imagers, a thin, strongly fluorescent film is placed in thermal contact with the infrared-absorbing layer and illuminated from the sides to excite the fluorescence of the film in such a manner that the infrared image focused on it will be converted into a corresponding visible image at the film, ready to be focused on and processed by an inexpensive digital camera. In order to function as described, the fluorescent material of the film must emit, at any resolvable point, a strongly temperature-dependent fluorescence intensity when illuminated with light of wavelength within the long wavelength “tail” of a strong electronic absorption band. Virtually all solid fluorescent materials show this property. A temperature coefficient of about 0.02 per kelvin is indicated within the range, but substantially higher coefficients are achievable.

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Prillings for Next-Generation Rocket Fuel

Joy Mann Simmons, Joseph Resnick,Ron Stewart, and Holden Lane,
Perry, GA

Next-generation solid-sphere prillings were developed that have secondary and tertiary matrixes comprised of microcrystalline hydrocarbon nano-articles for use as an advanced hybrid rocket fuel based on liquid layer hybrid combustion theory. The microencapsulation process and instrument is a NASA spinoff technology first used to produce glass microbeads in space, and later to spawn creation of an arsenal of oil spill cleanup, medical, pharmaceutical, and food products. This technology represents “future fuels” that produce a very thin, low-viscosity, low-surface-tension liquid layer on the fuel surface when it burns. Driven by the oxidizer, liftoff and entrainment of PCM-droplets and secondary nanoparticle hydrocarbon components greatly increase the overall fuel mass transfer rate simulating a continuous spray injection system with the fuel components vaporization occurring around the droplets convecting between the melt layer and flame-front, resulting in higher regression rates and exponential increase in thrust.

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