Selective Separation Sintering (SSS), a new 3D-printing process developed by a USC engineer to enable the construction of physical structures in space, won first place in the NASA In-Situ Materials Challenge. The competition was held in collaboration with the Kennedy Space Center and Swamp Works to advance construction and human habitation in space.

How else can we further space exploration, mused Behrokh Khoshnevis, other than building landing pads, roads, hangars, blast walls and radiation shields on the moon and Mars? Khoshnevis is the two-time NASA competition winner, Dean’s Professor of Industrial & Systems Engineering, Aerospace & Mechanical Engineering and Astronautics Engineering, and director of the Center for Rapid Automated Fabrication Technologies at the USC Viterbi School of Engineering.

It’s too expensive to rely on materials sent from Earth to build in space. In addition, using resources found in space could save considerable time.

Rocking it

The NASA competition mandated competitors to identify novel concepts in advancing the technology and methodology of utilizing materials found on the moon and Mars — regolith, crushed basalt rock or others — to construct structures or fabricate objects needed for future planetary and space missions.

Using synthetic material created by the Johnson Space Center that mirrors the existing gravel and material available on the moon and Mars, Khoshnevis and his team developed “a robotic fabrication process” that uses high melting-point ceramics such as magnesium oxide (readily available on the moon and Mars) and ordinary regolith (planetary soil) to produce tiles that could withstand the heat and pressure of exhaust plumes of landing spacecraft.

Selective Separation Sintering, Khoshnevis said, “is a novel powder-based additive manufacturing method that can build parts of various scale out of polymers, metals, ceramics and composites.”

Contour Crafting

The new SSS process builds on Khoshnevis’ existing Contour Crafting, a mega-scale 3-D printing process that captured the grand prize in a 2014 NASA competition. Khoshnevis demonstrated in a NASA Innovative Advanced Concept research project that Contour Crafting can use a mix of sulfur and regolith to build structures such as walls and hangars on the moon and Mars. While Contour Crafting is an extrusion-based 3-D printing process suitable for construction of large-scale monolithic structures, SSS is a powder-based method ideal for building smaller-scale objects such as interlocking tiles and bricks, as well as a large array of functional objects such as metallic parts.

“SSS is the only powder-based process that can effectively work in zero gravity condition and as such it is ideal for use in the International Space Station for fabrication of spare parts and tools,” Khoshnevis said.

According to the longtime engineer, it costs about $10,000 to launch a kilogram into low Earth orbit, $100,000 to send the same load to the moon and even more to send that cargo to Mars. He estimates that his team’s innovation could reduce the need for sending cargo from Earth, thus potentially saving agencies such as NASA considerable funds.

It could make space pioneering more cost-effective and feasible. Behrokh Khoshnevis

“It could make space pioneering more cost-effective and feasible,” he said.

“There are no viable, direct, high-temperature metal, ceramic or composite fabrication methods that can work in zero-gravity conditions. SSS will be the first such process,” he added.

Advantages at hand

Khoshnevis believes the SSS process his team created offers certain advantages, including speed, independence from expensive laser and electron beam technologies and even perhaps greater accuracy than these methods.

“There is high potential for the space and planetary use of this technology. SSS is a minimally complex but highly capable technology that can effectively assist planetary exploration, utilization and colonization,” he said.

The research team plans to further test the SSS process in a vacuum chamber of USC’s Astronautics Rocket Lab and NASA’s Kennedy Space Center facilities. The engineers hope to collaborate with local aerospace companies in the Los Angeles area.

More stories about: Aeronautical Engineering, Aerospace and Mechanical Engineering, Research