Additive Manufacturing of Large Structures Using Free-Flying Satellites

Abstract

In-Space Manufacturing (ISM) is being investigated as a method for producing larger, cheaper, and more capable spacecraft and space stations. One of the most promising manufacturing techniques is additive manufacturing (AM) due to its inherent flexibility and low waste. The feasibility of a free-flying small spacecraft to manufacture large structures using a robotic arm with an AM end effector has been examined. These large structures would aid the construction of a large space station or spacecraft. Using the Experimental Lab for Proximity Operations and Space Situational Awareness (ELISSA) at the Institute of Space Systems at TU Braunschweig, a process has been designed and tested which is capable of producing structures with arbitrary length. This process was demonstrated by manufacturing support free truss elements of unlimited length using a free-floating mobile robot. Avenues for further extending the process to produce structures of any size in 3D space are discussed.

Algorithms for Large Scale Additive Manufacturing in a Free-Flying Environment

“…The aforementioned setup is capable of 3D printing onto a stationary platform. The printing of truss structures with an unlimited length by splitting the structure into segments which fit into the robotic manipulator's workspace has already been established (Jonckers et al, 2022). However, the joints between segments constitute weak spots in the overall structure.…”

“…The coordinated movement of robot and free-flyer is harmonized through a common trajectory that contains target positions for both systems; the time step for position updates is dt = 60 ms. The robotic arm is able to adjust for position and orientation errors of the free-flyer through a previously developed control system (Jonckers et al, 2022). The TCP pose of the robotic arm within the global frame is calculated by combining the tracking information of the free-flyer from the optical tracking system and the position feedback of the robotic arm.…”

“…microgravity, vacuum, temperature gradients) has been demonstrated by several researchers showing no significant disadvantages to their respective counterparts manufactured under terrestrial conditions (O'Connor and Dowling, 2018;O'Connor and Dowling, 2019;Sacco and Moon, 2019;Quinn et al, 2021). However, the impact of the frictionless free-flying environment has only recently been investigated for a segmented AM approach of truss elements (Jonckers et al, 2021;Jonckers et al, 2022).…”

“…Thus, minimization of end effector errors were not as crucial for successful printing demonstrations. In comparison, we presented a closed-loop printing approach using a mobile base, achieving a printing accuracy of less than 0.3 mm, allowing the successful deposition of thermoplastic materials through a 1.2 mm diameter nozzle (Jonckers et al, 2022).…”

“…To improve print accuracy, we then developed a control approach to compensate for any remaining position error using the robotic manipulator. This enabled parts to be printed with a mean printing error of 0.27 mm (Jonckers et al, 2022). As the Free-flyer attempted to maintain a fixed position during the printing process, the size of components printed was limited by the robotic arm's workspace.…”