Researcher advances on-orbit robotic assembly of space structures

Bryce Doerr, Ph.D., has always felt inspired by the achievements of the U.S. space program. Having grown up hearing stories about the Apollo program and the moon landing, and witnessing the current investment to space exploration with the Artemis missions, Doerr knew he wanted to contribute to the development of technology to help progress humanity forward through the unknown.

Pursuing his passion, Doerr graduated from the University of Minnesota—Twin Cities with his doctoral degree in aerospace engineering and mechanics in 2019. In October 2019, Doerr joined the Intelligence Community (IC) Postdoctoral Research Fellowship Program and began conducting research on space robotics.

The IC Postdoc Program is administered by the Oak Ridge Institute for Science and Education (ORISE). The program offers scientists and engineers from a wide variety of disciplines unique opportunities to conduct research relevant to the Intelligence Community.

Doerr served his appointment as part of the Astrodynamics, space Robotics and Controls Laboratory (ARCLab) in the Department of Aeronautics and Astronautics at the Massachusetts Institute of Technology (MIT) located in Cambridge, Massachusetts. Under the guidance of his mentors Byron Knight, National Reconnaissance Office (NRO) Chief Scientist, and Richard Linares, a Charles Stark Draper Assistant Professor at MIT, Doerr contributed to research efforts focused on advancing the area of on-orbit robotic assembly of space structures.

Historically, the majority of spacecraft have been manufactured and assembled on the ground prior to being launched into orbit. However, many theoretical mission designs contain complexities that are constrained by the requirements of the launch vehicle, such as volume and mass. On-orbit robotic assembly would allow for the potential to enable complex designs of space structures as well as reduce costs in structure maintenance.

“The use of on-orbit additive manufacturing and robotic assembly allows for the flexibility of building large complex structures including telescopes, space stations and communication satellites,” explained Doerr.

“Currently, there are many Earth observing satellites investigating the Earth’s oceans and land masses, and there is a need to increase the longevity of these missions by on-orbit assembly. By enabling the autonomous robotic assembly of space structures, near-Earth science can be improved to help leaders make decisions on environmental change, managing resources, and responding to natural disasters.”

Doerr’s primary research involves the development of motion planning and control algorithms through the use of a linear quadratic regulator and rapidly-exploring randomized trees (LQR-RRT*), path smoothing and tracking the trajectory using a closed-loop nonlinear receding horizon control optimizer for a robotic free-flyer. Doerr is developing these algorithms using techniques usually applied to ground robotic applications. By extending research from sample-based motion planning to complex obstacle-ridden environments, Doerr hopes to push on-orbit assembly in a new direction.

Doerr is also contributing to the algorithm development for a robotic testbed called Astrobee. When completed, the hardware testbed will be used to test Doerr’s algorithms for various ground assembly experiments.

“When successful, these physical experiments will be applied on the Astrobee robots on the International Space Station,” said Doerr. “The approach is a natural generalization to repairing, refueling and re-provisioning space structure components while providing optimal collision-free trajectories during operation.”

During his fellowship, Doerr is gaining a variety of technical and soft skills valuable to his budding career. His research was recently published as an article titled “Random Finite Set Theory and Centralized Control of Large Collaborative Swarms” in the AIAA Journal of Guidance, Control, and Dynamics. Before the start of the pandemic, Doerr was also able to present at several conferences and exhibitions.

“The IC Postdoc Fellowship Program has been very supportive in my research endeavors,” said Doerr. “I am very excited to continue what I do.”

When his fellowship concludes, Doerr plans to continue his research at the NASA Goddard Flight Research Center Attitude Control Systems Engineering Branch.

“My goal is to develop cutting-edge research in new technologies for new space missions,” said Doerr. “This includes areas of control of large collaborative swarms and on-orbit assembly, as well as the combination of the two. By having the flexibility of working for a government agency, I can produce work that aligns with both my and the public’s interest.”

The IC Postdoc Research Fellowship Program is administered by the Oak Ridge Institute for Science and Education (ORISE) under an agreement between the Office of the Director of National Intelligence (ODNI) and the U.S. Department of Energy (DOE). ORISE is managed for DOE by ORAU.