Thrusters have been used to move spacecraft since the 1960s, but are still rare on CubeSats. Now, many missions opt for nano satellite platforms like CubeSats to meet the required objectives with lower launch costs and shorter development times. However, current CubeSats generally provide only coarse attitude control and do not allow for orbit adjustment. In the Surrey-sponsored TRACSat (Target Recognition and Acquisition CubeSat) project, students from University of Colorado at Boulder aimed to demonstrate technology that allows rapid ground-based testing and measurement of precise CubeSat maneuvers and thruster control algorithms.
The biggest challenge for this project was size—most CubeSats are less than 3 kg and smaller than 10 x 10 x 30 cm. The team used Simulink® to rapidly prototype and auto-code closed control loops that read attitude information from onboard and external wireless sensors to control cold gas propellant and maneuver their CubeSat-sized engineering model. With the help from a Wii remote infrared camera and a low-friction testing surface like an air hockey table among other parts, the team was able to maneuver the engineering model reliably and accurately, as you can see in the video below.
The team has wrapped up the end of the academic year and achieved all of its primary objectives. They successfully:
Tested different variations of control system algorithms with a 30-minute turnaround time from control loop design change to hardware-in-the-loop maneuver test.
Assessed the impact of these different algorithms on propulsion consumables.
Verified that the vehicle could translate 0.5 m, rotate 30 degrees, and then maintain station keeping within a 2.5 cm radius and 2.5 degrees of target orientation for 30 seconds.
They concluded that their system has a position sensor accuracy of ±0.4 cm and there was an impressive 99.9% confidence over the actual testing surface (the low friction air table).
These are encouraging results, as an accurate CubeSat propulsion system such as TRACSat could pave the way for CubeSats being used in proximity operations missions from spacecraft maintenance and repair to exploration, making these missions more accessible and quicker and cheaper to launch.
When they weren’t developing and tweaking TRACSat,
the team was presenting their findings at conferences around the world, including the 2nd
IAA Conference on University Satellite Missions and Cubesat Workshop in Rome, Italy, and the AIAA region 5 (pdf)
student conference in April, where they took second place in the group projects category. They also carried out live autonomous demonstrations every 20 minutes at the Senior Design Symposium at the University of Colorado. TRACSat didn’t need instruction–even when it was pushed out of its station keeping area by observers, it independently returned to the right area. At the end of the academic year, the University of Colorado Department of Aerospace Engineering recognized the team’s success with the “Best Overall project” and “Best Software” awards.
The students have achieved a fantastic amount in such a short period of time and we’re thrilled to have been able to support them in this project. We were so impressed with the students that we have taken on one of the team, Michael Trowbridge, as a summer intern. Michael specializes in software and will be participating in the next University of Colorado
design project sponsored by Surrey, while he works on his Master’s thesis.
TRACSat Team Members:
Mike Opland (Project Manager)
Andrew Broucek (Systems Engineer)
Sarah Smith (Electrical Lead)
James Bader (Mechanical Lead)
Zachary Cuseo (Guidance, Navigation and Control Lead)
Alex Kim (Position and Orientation Determination Subsystem Lead)
William Ryder Whitmire (Propulsion Lead)
Michael Trowbridge (Software Lead)