Samples of lunar regolith have included small glass spheres. Most literature has suggested the small spheres were formed by meteorite impacts. The resulting transformation of kinetic energy to thermal energy caused the lunar surface to melt. The process yielded glass spheres. Recreating a meteorite impact that yields glass spheres is very challenging. Furthermore, the melting temperature of certain minerals on the Moon precludes the use of standard thermal techniques.
Glass spheres are created by using a thermal and pneumatic process. The process allows extremely high-meltingtemperature material to be transformed into sub-750-micron spheres. The thermal and mechanical process developed transforms the molten material to the lowest energy morphology, a sphere, while locking in the glass chemistry.
To produce a high volume of sub-750- micron glass spheres, the feedstock material was melted with a plasma system. The system uses high-power, remotely coupled electric plasma. The molten material is then routed through a molybdenum orifice and allowed to fall vertically by gravity. Approximately one meter from the discharge, a highvelocity pneumatic jet is positioned perpendicular to the glass stream. At the impingement zone, the molten glass material is pneumatically removed from the primary stream path and rapidly cooled to glass morphology while traveling to the collection area. At the collection area, the spheres are mechanically collected.
The integrated plasma system and mechanical forming process allow a very wide variety of material to be processed into spheres. Also, the rapid pneumatic quench locks ensure glass morphology and precludes any significant devitrification.
Glass spheres are currently used in a wide variety of consumer and commercial applications. The ability to thermally react feedstock materials at plasma temperatures extends the range of possible glass chemistries available. The demonstrated ability to produce spheres directly from a molten glass stream increases the upper diameter limit realized in traditional solid to sphere processes. Examples of current research work using the plasma process include production of high-strength glass spheres for drilling proppants, and the integration of catalyst materials in bio-degradable glass for ground water remediation applications.