A rubble-rousing idea

By Robert C. Jones Jr.[email protected]08-28-2024

Discarded alloys and other materials scavenged from obsolete military equipment could soon be serving a useful purpose high above the planet's surface instead of being relegated to a scrapheap, thanks to the efforts of a University of Miami College of Engineering researcher.

In a high-tech recycling process, Charles "Chip" Tomonto and his students will convert scrap metal into a powder, then use those fine particles to 3D-print lightweight pressure vessels that will become vital parts of instrument-laden sounding rockets typically used to conduct scientific experiments in the upper atmosphere.

It's all part of Rubble to Rockets (R²), an initiative of the Defense Advanced Research Projects Agency (DARPA) in which scrap metal from U.S. forward military bases will be converted into reusable materials.

"There's a lot of structural material that is scrapped at military sites, and that material is fully qualified material that meets mil-spec (military specifications) standards. But the components that were built with that material are no longer needed, so they're often scrap," said Tomonto, a professor of professional practice in the Department of Mechanical and Aerospace Engineering, who is the co-principal investigator on the project. "There's literally volumes and volumes of that scrap material sitting at major military installations everywhere."

When the first shipment of scrap metal from the Department of Defense arrives at the college, Tomonto and his team of graduate assistants will begin the highly technical process of converting it into pressure vessels, casting the material into ingots and using a lathe and ball mill to crush those ingots into a fine-grained powder that will be used in a 3D metal printer to fabricate the pressure vessels. An inductively coupled atomizer will spheroidize the powder before the printing process.

The team will perform its tasks at the Advanced Materials Innovation Lab inside the McArthur Engineering Building. "The military mandates a very high-quality material," said Tomonto, who earned a Bachelor of Science in mechanical engineering from the University. "So our baseline material is going to be very good. We're going to analyze the baseline material, and if we have to make any modifications, we will."

Teledyne Scientific Company and the University of Wisconsin-Madison are partners on the project.

Manufacturing vital components for sounding rockets is but the initial phase of the nascent R² project. The initiative's primary goal is to develop and perfect a design and production process in which components and parts for a wide range of other products can be built from scavenged and scrap materials at key military bases in regions where supply chain networks are disrupted.

"Building a framework that can enable the manufacture of structures out of anything, anywhere, and at many sizes would break the status quo for manufacturing in resource-contested environments," said Hunter Martin, DARPA's program manager for R². "We're focusing on sounding rockets for proof of concept because they represent a single-use structure with multiple components and complex structural requirements. But we anticipate broad applicability to a wide range of manufacturing use cases-from spare parts and infrastructure repair to system production."

Rubble to Rockets will offer an ideal learning experience for graduate and undergraduate students, according to Tomonto. "We have full capability at the lab to make and analyze our own powder, come up with the parameter sets for 3D printed material, and then test the finished result. So our students will be able to leverage those skills into employable positions," he said.

"I am passionate about sustainability and circularity in engineering," said Reese Simancek, a senior majoring in mechanical engineering. "So this project gives me the opportunity to explore recycling in the engineering field and gain valuable experience with it before pursuing my career as a sustainable engineer."

For Mary Goncharenko, a senior majoring in mechanical engineering, the project represents a connection between two fascinating fields: aerospace engineering and 3D metal printing. "Both have strong prospects in industry and lend themselves well for further investigation in potential graduate research," she said. "Moreover, sustainability is a critical factor for the future of engineering. So being able to work with it as a parameter in this project is valuable experience for my future professional endeavors."