Carnegie Mellon University faculty and students recently experienced something few ever have: weightlessness. Aboard a plane that follows an unusual flight path – steep climbs followed by dramatic dives – members of the Robotics Exploration Lab in CMU’s Robotics Institute (RI) put their research through critical tests.
During each parabolic arc, the plane creates about twenty seconds of microgravity. Some passengers floated to the ceiling while others rotated almost comically in midair. But for the CMU team these brief moments aren’t just for fun; they are a rare opportunity to document how vast deployable space structures may act in the true zero-gravity of space.
These flights supported the work of Mitch Fogelson, recently graduated Mechanical Engineering Ph.D., and Zac Manchester, associate professor at the RI. In collaboration with researchers from Northeastern University and the University of Washington, Fogelson and Manchester have been working to create massive foldable structures small enough to fit on a rocket, yet capable of expanding up to a kilometer long once released into orbit, with the goal of supporting astronauts in microgravity environments and long-term mission planners.
The team invented two new structures: Pop-Up Extending Trusses (PETS) and Hierarchical High-Expansion Ratio Deployable Structures (HERDS). Both inventions can serve to support large space structures for projects like future space stations, as well as rapidly deployable infrastructure for earth applications, such as cell communication towers that can stow in a backpack for disaster relief. But with the complexity of the designs, parts of these structures can occasionally jam and break, creating a need for highly accurate testing environments to make improvements.
“With so many components and moving parts, it is very difficult to simulate the full deployment dynamics of these structures on computers,” said Manchester. “The flights were very helpful to physically model the subtle details and see how the structures truly behave in real-life zero gravity.”
Manchester leads the Robotics Exploration (REx) Lab, where the group focuses on control, motion planning and navigation for robotic systems for space exploration. The lab includes a wide range of expertise from students around the university, creating projects that require multiple skill sets and interdisciplinary communication.
In that spirit of collaboration, Fogelson joined REx Lab and brought his mechanical engineering expertise to building the deployable structures. His skills complemented the lab’s existing strengths, helping the team tackle the complex mechanical challenges that come with designing massive foldable, durable and efficient structures capable of compacting down before launch.
The team developed 1/10th scale prototypes of their inventions in the lab and then sized down to 1/1000th scale prototypes to bring on board the flights and observe their dynamics. To capture adequate data, they had to act quickly in order to complete their experiments in the allotted amount of time in zero gravity.
“To stay efficient, we built an enclosure to keep the structures in during the flight. To track motion, we put reflective stickers on them and used eight high-speed GoPro cameras and four OptiTrack cameras.” said Fogelson. “During the tests, we spun the structure and then deployed it and captured all of the motion data.”
The team were able to see how their inventions behaved in true zero-gravity conditions, as close to space as possible. The systems deployed using centripetal force, with the spin rate reduced drastically as the structure prototypes fully extended. The structures also flipped over due to the Dzhanibekov effect, also known as the “tennis racket” theorem. The documented behaviors gave the researchers key insights into the next steps in modifying the structures for deployment at full scale.
The flight testing opportunity came as a result of the NASA Innovative Advanced Concepts (NIAC) Program. The team first received a phase-one award, a short-term phase where the team proved the feasibility of the project. After completing phase one, they received a phase two award to support two more years of work, which allowed the researchers to further develop their structures.
The team’s performance in phase two earned them two flight experiences from the NASA Flight Opportunities program in partnership with the Zero Gravity Corporation (Zero-G). Zero-G offers specialized flights in a Federal Aviation Administration-approved parabolic flight provider to scientists to carry out in-person experiments in microgravity conditions.
The work doesn’t stop at test flights. After years of intensive research, a collaboration with NASA and successfully defending his Ph.D. thesis, Fogelson has gone on to create Beyond Reach Labs, a company dedicated to expanding the work of CMU and NASA to more real-life applications. He credits the Zero-G flight opportunities as a key component in turning his vision into reality.
“Getting the chance to go on a zero gravity flight in person was a once-in-a-lifetime bucket list experience for me,” said Fogelson. “I’ve dreamed about it since I was a little kid.”
For More Information: Aaron Aupperlee | 412-268-9068 | aaupperlee@cmu.edu