This document describes an approach to develop a fully distributed multipurpose autonomous flight system. With a set of hardware, software, and standard flight procedures for multiple unmanned aerial vehicles (UAV), it is possible to achieve a relative low-cost plug and play fully-distributed architecture for multipurpose applications. The resulting system comprises an OptiTrack motion capture system, a Pixhawk flight controller, a Raspberry Pi companion computer, and the Robotic Operating System (ROS) for internode communication. The architecture leverages a secondary PID controller with the use of MAVROS, an open-source Python plugin for ROS, for onboard processing and interfacing with the flight controller. Featuring a procedure that receives the position vector from Optitrack System and returns the desired velocity vector for each time-step. This facilitates ease of integration for researchers. The result is a reliable, easy to use an autonomous system for multipurpose engineering research. To demonstrate its extensiveness, this paper shows experiments of a robotics navigation experiment utilizing the fundamentals of Markov Decision Processes (MDP) running at 60Hz, Wireless and with a network latency below 2ms. This paper reasons why fully distributed systems should be embraced as it maintains the reliability of the system with lower cost and easier implementation for the ground station. Combined with an intelligent choice approach for developing software architecture, it encourages and facilitates the use of autonomous systems for transdisciplinary research.
The ability to additively manufacture structures on-orbit has the potential to fundamentally alter the traditional paradigm for how large spacecraft are constructed and launched into space. The space environment presents several unique challenges for additive manufacturing, including the need to operate in a vacuum. This paper presents the design, analysis, and test results for a passively cooled fused filament fabrication (FFF) 3D printer capable of manufacturing parts out of engineering-grade thermoplastics in the vacuum of space. Four high-temperature materials were successfully printed in high vacuum, including polyetherketoneketone, carbon-nanotube–polyetherketoneketone, polyetherimide, and carbon-nanotube–polyetherimide. Over 100 test coupons were printed in a vacuum and tested to confirm the feasibility of applying the FFF process in this environment. Lessons learned were documented throughout the vacuum printing test campaigns and are discussed here. This paper is part of a two-part series. Part I presented results for using a low-temperature hotend capable of printing hobby-grade materials in high vacuum and documented initial findings and lessons learned. Part II presents the results for a high-temperature hotend capable of printing engineering-grade plastics that are suitable for on-orbit manufacturing. The combined results of the two papers in this series can be used to inform future on-orbit additive manufacturing.
On-orbit manufacturing and assembly have become major research and development topics for government and commercial entities seeking the capability to build very large structures in space. Additive manufacturing is well suited to this paradigm since the process is highly automated, produces little material waste, and allows for a large degree of geometric freedom. This paper presents a design for a 3D printer that operates in high vacuum. The vacuum 3D printer has completed multiple thermal vacuum test campaigns, with dozens of parts printed to date using low-temperature thermoplastics. Testing of material coupons shows that samples printed in vacuum have strength properties generally within a standard deviation of samples printed at ambient pressure. The overall results from multiple successful tests of the vacuum 3D printer promote the feasibility of on-orbit additive manufacturing while exposed to the space environment. This paper is part one of a two-part series. Part I presents the results using a low-temperature hotend capable of printing hobby-grade materials and documents some initial findings and lessons learned for applying FFF in vacuum. Part II presents the results for a high-temperature hotend capable of printing engineering grade plastics that are suitable for on-orbit manufacturing. The combined results of the two papers in this series can be used to inform future on-orbit additive manufacturing applications as well as potential uses on future moon missions.