On-orbit and in-space manufacturing: Designing future structures based on novel metamaterials Kim Roth

Large and extended structures such as satellite components, solar arrays and antenna reflectors are required for space missions as well as defense and other applications. However, traditional space structure designs are mostly based on deployable concepts with strict limitations in size and mass. They require compact packaging for transport to space and are deployed in space prior to operation. Since deployable structures launch from Earth, they are designed, built and tested in on-ground conditions while accounting for their survival during launch. Yet, the operational conditions in space are quite benign compared to launch loads. Traditional designs limit the advancement of mass efficiency of space structures and also do not address the needs for future space structures manufactured on orbit.

With funding from DARPA, the Defense Advanced Research Projects Agency, a University of Michigan team is working toward new solutions, designing novel material and design technologies for large and extended space structures that are manufactured not on Earth but rather on orbit or in space.

Principal investigator Serife Tol, assistant professor of Mechanical Engineering, and co-PIs Ellen Arruda, the Maria Comninou Collegiate Professor of Mechanical Engineering; Xiaoming Mao, associate professor of Physics; and Anthony Waas, the Felix Pawlowski Collegiate Professor of Aerospace Engineering recently received $1.46 million for the first phase of the project. This first phase targets solar arrays, while the second phase targets RF antenna designs and the third phase, optic systems.

“Today’s space designs are optimized for the design-build-test-launch-deploy paradigm of the past, and in most cases baseline designs have not changed for decades,” Tol said.

Innovating conventional designs and materials

The U-M team is proposing a new approach. “Since the needs of future space structures are different, the materials and the designs we’re proposing are also different and innovative,” Tol said.

Instead of using conventional materials, the team will combine topological, auxetic, and dissipative metamaterials with new structural designs to achieve novel space structures that can be manufactured on orbit or in space. The work will achieve high-precision future structures that are mass-efficient (light weight), resilient and tolerant to post-damage.

The metamaterial designs the team is proposing will allow greater and programmable stiffness, lighter weight, damage tolerance, and improved stability over conventional materials. In addition, the periodic nature of metamaterials will enable modularity and modular assembly of the space structures.

Unlike conventional materials, the properties of metamaterials are determined by their unit structure rather than the material itself. By changing the structure of a metamaterial, investigators can engineer and control exotic material properties.

“Topological states of matter is a fascinating concept that revolutionized physics in the past decades. Now is its turn to shift the paradigm of engineering,” Mao said.

For the in-space manufacture of large and extended structures, the team is designing metamaterials with a modular structure using truss-like designs and other concepts. This will enable larger space structures that also have significantly reduced mass over conventional designs.

At the same time, the new designs don’t compromise stiffness. “These metamaterials can have some extraordinary properties, including high stiffness and damping, which helps ensure high-precision tolerances that space structures require,” Tol said.

Vibration damping is necessary in order to stabilize the large structures, and the larger the structure, the more control required. Current techniques, based on active control, add a great deal of complexity. But the new designs the team is proposing will include dissipative metamaterials that will enhance passive damping properties, giving the structures greater capacity to absorb unwanted vibration and yield quick stabilization.

Improving resilience

Resilience and damage tolerance also will be an important part of the design of the new materials and structures. Some of the topological metamaterials the team is working with can be designed to localize and control damage, such as in the case of the meteor striking a solar array. They also can be designed to overcome other challenges in antenna design, such as a type of undesirable curving known as the pillowing effect.

“Controlling the in-space shape of the antenna using metamaterials offers tremendous possibilities for expanding the range of frequencies beyond what is possible today,” Waas said.

Affording new material options and applications beyond space

The use of conventional materials that must both survive launch and function in space has meant a limited range of materials options suitable for large space structures. With the team’s proposed materials and designs, however, the range of possible materials widens considerably.

“Such a paradigm shift in the materials that can be used in the design of in-space built structures provides a tremendous opportunity for creativity and innovation,” Arruda said.

The team expects that many of the same manufacturing principles and materials designs it proposes will have applications far beyond space.

“This work is advancing our understanding of topological and dissipative metamaterials and how to design and manufacture high-precision, resilient structures with them,” said Tol, “and it will certainly pave the path for other interesting applications.”