Metal Production Away from Earth
Introduction
Producing the materials needed to fabricate structures and vehicles is a critical requirement for the long-term occupation of space. If everything had to be delivered from Earth, the cost would be overwhelming. The process developed here will allow the production of iron and nickel almost anywhere in the solar system in a form appropriate for use in Additive Manufacturing without consuming any material that must be brought from Earth. Once in the powder form the metals, if desired, can readily be converted to other forms such as rods, ingots, and sheets for use with conventional fabrication methods. Therefore, this process will allow supplying both additive and conventional fabrication processes with metal.
The need to produce materials in space to avoid the cost of lifting them from Earth is an important part of NASA’s exploration roadmap. Long-term occupation of space requires a supply of metal suitable for the fabrication of various components and structures. While astronomical objects are rich in the desired metallic elements, these elements are in the form inappropriate for use in Additive Manufacturing processes. This project aims to develop a process to convert material from its native state (typically an oxide dispersed in a silicate matrix) to one suitable for use in Additive Manufacturing methods to allow the direct fabrication of complex parts in space.
NASA desires to produce several metals off Earth (i.e., on the Moon, on Mars, or near asteroids). These include iron, aluminum, magnesium, and nickel in forms suitable for use in AM. These elements occur throughout the solar system, generally in oxidized forms (e.g., MgO, Al2O3, Fe3O4, and NiO), which must be reduced using materials available in the immediate area (i.e., with little, if any material that has to be brought from Earth). The exception to this is meteoric and asteroidal iron and nickel, much of which is present as reduced metal. It is important that the developed process be as efficient as possible and that any compounds consumed (other than the metal ores) are regenerated as part of the process.
Mining astronomical objects such as meteorites and comets for metal is not a new concept. Much of the nickel used in North America comes from deposits near Sudbury, ON. These deposits are the result of an asteroid or comet impact that occurred nearly two billion years ago. As noted above, some classes of iron-nickel meteorites are largely composed of reduced metal, ready for conversion to a useful form, and used. Remote surveys of asteroids indicate that iron and nickel rich bodies are not uncommon, and, with the recent passage of legislation at the federal level, these resources can be considered fully available for exploitation. In addition, the surfaces of both the Moon and Mars, are known to be rich in iron, with some of the lunar material already in reduced form (and highly dispersed). Iron is the third most abundant element on the lunar surface and is also common on Mars, with nickel even more common.
Results: First, we tested our approach on neat metal oxides (NiO and Fe2O3). Photos of processed powders are shown below. After tuning processing conditions, nearly 100% conversion of oxide to elemental metal was achieved for both Ni and Fe.
Then, using identified process conditions the conversion of Mars Regolith Simulant was performed. Oxide conversion was 176% (which is IMPOSSIBLE!!! oh wait…). MMS-2 contains Iron Oxide (only 18%) and other compounds such as silicates (44%), Aluminum Oxide (13%), Calcium Oxide (8%), Magnesium Oxide (7%), Sulfates (6%), and trace elements (4%). Oxide conversion was calculated based on the mass of Iron Oxide only. Clearly, processing conditions affect other compounds in the mix, which leads to mass loss and hence elevated oxide conversion percentages.
