NASA GODDARD WALLOPS FLIGHT FACILITY
CubeSat ACS Tested System Testing
“The objective of the internship was to test the systems that form a CubeSat Attitude Control System (ACS) testbed that will allow guidance, navigation, and control engineers to test the functionality of their ACS. There are four individual systems designed to test the ACS unit’s various aspects: a torque measurement system, a dipole measurement system, and two air bearing systems. The torque measurement system uses a three sensor force table designed to measure reaction forces produced by reaction wheel torques. The system utilizes highly sensitive piezoelectric sensor technology, charge controllers, and a high resolution data acquisition system to process the data. The dipole measurement system uses a turntable and boom system to measure 20-40% of the magnetic dipoles produced by the spacecraft. Magnetometers on the end of the boom measure the magnetic footprint of the CubeSat, which is spun on top of the turntable. One and three degrees of freedom (DOF) air bearings are used to test phasing of the spacecraft about multiple axes in the air bearing system. A sun light source is used with the bearings to provide an input for spacecraft sensors to use in a feedback loop to the control software.”
Findings and Results
“While using the torque measurement system, we found issues with excessive noise in the data, so several tests were run to identify that the noise was being caused by vibration external to the setup. Sorbothane visco-elastic material was chosen as a potential vibration damping solution, and isolator pads were sized to be within its optimal performance range. Once obtaining the sorbothane and a foam memory mattress, we plan to test both materials to see if either reduce the noise seen in the data.
“My main task with the dipole measurement system was to redesign the boom stand to resolve an issue with loose tolerances that allowed the boom to drift. After using Inventor to remodel the stand, performing stress analyses, creating drawings, and assembling the stand, the new stand demonstrated that the drift issue was resolved. However, we found the new boom stand had a stiffness issue. I have designed a new support for the stand and am currently waiting on parts to assemble it.
“After repairing the faulty light source used for the air bearing systems and tracing an issue with the primary wiring harness and coarse sun sensor, testing was performed with load cells to mass balance the air bearing test assembly. Currently, I am working to identify an alternative load sensor system with high resolution and stability.”
“In addition to tours of the different parts of the facility (sounding rockets, balloons, aircraft hangars, range control center, island launch site), I had the opportunity to attend seminars and discussions led by other mentors in the engineering branch. In a series of workshops, I had an introduction to stress analysis software FEMAP and NASTRAN. I also learned how to perform stress analysis calculations in Inventor and using NASA 5020 fastener analysis.
Overall, I found the work I did this summer engaging. While there were times where it was difficult for me to adjust to a new environment, I was surrounded by friendly and extremely helpful professionals and interns at work who helped make this experience enjoyable. I liked coming to work and learning something new everyday. I also liked the feeling of doing work that really has an impact at NASA.
Using my acquired knowledge of CubeSats and experience in designing test systems and collecting data, I hope to apply to a similar research lab at college. I am also currently in charge of designing the mechanical braking system on the Hyperloop project team at Cornell, so I hope to bring over some of the designing skills I gained here at this internship. Looking towards my career, I believe CubeSats have a variety of practical applications, both in academia and industry. It is rapidly developing and I am excited to be at the forefront of technology that will revolutionize the future of data collection and exploration in space. As an aspiring mechanical engineer interested in the aerospace industry, what I take away from this internship will be critical in any work I do with satellites. In a broader sense, the problem solving and critical analysis skills I am developing by creating and improving upon system designs will also help me in any engineering career I pursue.”