JPL published its annual JPL Technology Highlights 2022, the first with new Director Laurie Leshin, who formally assumed her position on May 16th, 2022, succeeding Michael Watkins, who retired in August 2021, and new Chief Technologist Dr. Tom Cwik. As pointed out by Douglas Hofmann, Senior Research Scientist (SRS) and Principal at NASA Jet Propulsion Laboratory and a well-known figure in the global AM industry, additive manufacturing research was represented in three projects. The first was on efforts to 3D print aluminum reflectors for spacecraft antennas with topology-optimized backing structures for thermal stability. This was led by Paul Goldsmith, with much of the printing work done by Ryan Watkins of the Technology Infusion Group. The second was on the development of high-performance magnetic shielding produced by DED. This method allows for complex shapes to be produced from magnetic materials, like mumetal, and also functionally graded multi-metal alloys for magnetic applications. This work was led by Samad Firdosy.
Lastly, Hofmann’s own work with Caltech on jamming 3D printed fabrics, published in Nature, was also highlighted. This work has taken on a new life led by Tent Bordeenithikasem in a new collaboration with Caltech to make shape-changing antennas using printed fabrics. “Additive manufacturing still has many exciting areas for contribution in NASA spacecraft and rovers,” Hofmann said. “One of our biggest accomplishments in AM at JPL, other than the printed parts on the Mars rover, has been the establishment of a flight-qualified process for producing aluminum and titanium parts through LPBF. This will enable us to print parts for our spacecraft and rovers and also to help other NASA centers with their efforts.”
The 3D printed fabric of spacecraft
JPL has developed a new 3D printable fabric that can be stiffened into a desired shape after deployment in space. These shape-morphing materials, inspired by chain mail armor, are fabricated by printing interlocking particles that can each independently move a short distance, allowing for customized configurations, ideal for specific purposes. These flexible sheets can then be rolled or folded into very small dimensions to be packed into a rocket fairing for launch. Creating a morphable structure requires a general, but not necessarily exact, knowledge of the final rigidized structure as well as designing appropriate interlocking particles.
The sheets can be shaped while they are flexible, and the stiffness can be tuned by varying the pressure, to achieve the desired shape. Then force is applied to adjacent sheets as they jam together, interlocking into a final, rigidized configuration. These structural fabrics have many potential applications in both NASA missions and consumer products. They can be used as deployable radiators, antennas, solar panels, radiation protection blankets, or micrometeoroid shields. They could also be used as body-conforming exoskeletons for astronauts exposed to long-duration microgravity.
On Earth, the structural fabrics could be used in healthcare as adaptive casts that adjust their stiffness as an injury heals or as impact-absorbing clothing for firefighters or soldiers. Their characteristic of being foldable and stowable, then deploying into larger, rigid shapes once in space, will result in much larger and customizable components shaped for optimal performance.
EM shielding via AM
A multi-material magnetic shield created with blown powder consolidation technology showed improvements in shielding performance. As NASA’s robotic spacecraft become increasingly capable of detecting faint signals from stars, planets, and other targets, they also become more and more sensitive to interference from onboard machinery like reaction wheels, electric motors, and cooling systems.
Anything using an electric motor, for example, can be a problem for sensitive magnetometers. In traditional designs, electronically “noisy” devices are shielded by metallic enclosures. Complicating these designs is the need to create intricate shapes to maximize the effectiveness of the electromagnetic shield— and these complex designs can be very difficult to fabricate. New techniques in use at JPL are leveraging the strengths of additive manufacturing to create better magnetic shielding more quickly and easily than ever before.
Using a process called blown powder laser deposition, metallic dust is forced through a nozzle, using an inert gas, directly into the beam of a high-powered laser. The resulting melted metallic blob fuses to the emerging part, which is built up layer-by-layer under computer control. By changing the composition of the powder, different metallic alloys can be deposited where they are most effective. This enables the creation of exotic parts that cannot be made using any other method and in far less time than current processes require. The result is more effective shielding with less mass and at a lower cost than previously available, leading to more capable spacecraft that can be smaller and lighter than anything that has gone before.
In another one of the JPL Technology Highlights 2022, additive manufacturing enabled the fabrication of high-performance, thermally-stable antennas for astronomy and remote sensing. Designing and fabricating antennas for spacecraft and high-altitude balloons is difficult. By their very nature, antennas are bulky, and building them to withstand the stresses of flight and maintain dimensional stability has been a challenge. Submillimeter antennas, which are used in a variety of Earth observation, planetary science, and astronomy applications, can be fragile as well. Since they operate on tiny wavelengths, they must be free of the smallest imperfections to work properly and to be capable of operating across a broad range of temperatures.
Traditionally, these antennas have been fabricated using glass forms to create the antenna’s surface, over which a thin reflective material like nickel is deposited. A supporting structure, made of metal honeycomb or strips, is then glued to the back. This process is time-consuming, exacting, and prone to manufacturing errors. The resulting antennas also have potential shortcomings when operating in extreme temperatures, as the materials expand and contract at different rates, introducing stresses and possibly uneven deformation into the antenna.
JPL engineers are experimenting with a new process that involves additive manufacturing that is low-cost, can be readily adapted for different applications, and is straightforward to accomplish. This new approach uses a single material to create both the support structure and the reflecting surface, which results in a greatly simplified manufacturing process and a single coefficient of expansion—the entire unit reacts to temperature changes uniformly. This results in fewer stresses on the antenna and less deformation, providing a superior signal during use.
By printing the antenna from aluminum powder, more complex antenna designs can be created with reduced mass, resulting in mission-optimized shapes that cannot be made using traditional fabrication techniques. By using sophisticated design software, the components of the antenna’s supporting elements can be made thinner or thicker as required, which further contributes to extremely high performance, efficient design