Expanding the boundaries of 3D printing parts for space
Crews and supplies regularly travel to the International Space Station, Space X’s Falcon 9 rocket has launched more than 100 times, and the US shuttle program ran 135 missions. Nonetheless, there’s nothing routine about the controlled explosions that blast people and cargo into space. Nor is there anything routine about the extreme conditions faced by humans and equipment once outside the protective bubble of the earth’s atmosphere.
Producing spacecraft, launchers, satellites, and equipment for operation in space is a demanding and elite niche into which additive manufacturing fits quite nicely. The parts involved in the space economy tend to be the high-value, low-volume items that benefit from a digital manufacturing process. Metal additive manufacturing of aluminum alloys, with its ability to produce lightweight, strong parts with exceptional thermal management properties, is particularly suited to this sector.
Additive manufacturing has already made inroads with both traditional space technology companies and new space entrants. Relativity Space is developing 3D-printed rockets, and a 3D-printed thrust chamber prototype has been tested for Europe’s lightweight Vega launcher. Boeing’s space division said in 2019 that 70,000 3D-printed parts are in use by its commercial and defense programs.
Advanced powders improve reliability
One breakthrough that will further advance AM in the space sector is the development of advanced, high-performance metal powders. By virtue of their consistent physical properties, these materials offer significant gains in part uniformity, process reliability and production speed.
“The uniform nature of our aluminum alloy powder ensures that parts are produced with reliable and consistent mechanical properties,” explains Martin Conlon, CTO, Equispheres. “The minimal variance in our performance results provides design engineers the statistical confidence to produce stronger, lighter parts.”
The mechanical variability of coupons printed using Equispheres’ powder is considerably less than those made of traditional powder available on the market (based on an analysis of publicly available data). The reduction in variability provides the statistical confidence to design engineers to increase the “a-basis design allowable.” This, in effect, enables engineers to design and build parts that are 30 percent lighter or 30 percent stronger.
Precise 3D printing
In addition to the weight optimization possibilities of Equispheres’ powder, one of the company’s newer products offers significantly improved dimensional accuracy. This is particularly relevant for thermal management applications. Equispheres Precision line of powders demonstrates up to 50 percent improvement in dimensional accuracy.
The biggest advantage AM provides for thermal management is the ability to create ultra-high surface area parts, allowing for high heat transfer rates. AM also permits complex surface geometries optimized for convection. These advantages are multiplied when using advanced metal powders with the precision to achieve narrow, closely packed fins.
Satellites, for example, incorporate batteries, fuel cells, solar panels, communications systems, electrical components, and antennas. They move in and out of direct sunlight, so they vacillate between temperatures ranging from 120C to -100C. Thermal management of on-board components is vital for long operational life.
“The reality is, in the space industry, there are a lot of low-volume items, and additive manufacturing is a cost-effective method for that type of production,” says Evan Butler-Jones, Director of Applications Engineering at Equispheres.
Not all powders are equal
Some of the opportunities for additive manufacturing in the space economy will only be feasible with high-performance feedstocks, such as those produced by Equispheres. Particle-to-particle consistency forms the foundation of Equispheres’ powder technology. Equispheres’ powder has a particle size distribution range half as large as competitive products. Compared with gas atomized powders, Equispheres powder has 10x less specific surface area per unit mass, which improves flowability in powder bed fusion processes. More important, Equispheres powder contains 10x fewer fines (i.e. particles with a diameter of less than 10um) than traditional gas atomized powder.
Shaking off the shackles of gravity means exposing equipment to the harsh realities of space: temperature extremes, radiation, pressures. We can expect to see more adoption of aluminum powder and additive manufacturing for repeatable, reliable production of parts for spacecraft and satellites.