CubeSats, kinds of small satellites, are growing in popularity due to their space applications (such as remote sensing, navigation, communication, and earth observation) whilst being affordable to private entities. Their small size allows advanced microchips and other small components to compose a system with lowered volume, mass, and cost. However, as these components require power, without being able to afford much stowed-volume aboard the craft, power generation becomes an essential concern. The goal of HDAS is to maximize the energy-generation potential of a solar array on a CubeSat via articulation that operates both autonomously and cheaply. HDAS plans to do this via creating a passive-articulation system which ranges ±45o along two axes of the solar array using shape-memory alloy technology. This will allow the array to face the sun as perpendicular as possible, and thereby increase the efficiency of the deployed solar panels. HDAS is constraining the stowed deployment/articulation device to fit within a 10 x 10 x 6 cm3 space and this system is expected to produce a minimum of 340 W and weigh less than 2 kg.
The Small Satellite Solar Array Deployment System is part of the CubeSat/Nanosatellite industry, which is a subdivision of the Aerospace and Small Satellite industries. The cost effective nature of CubeSats allows for a relatively cheap and easy entry into this industry, creating lots of competition. Many large and small Aerospace companies, such as Tyvak and SNC, as well as some Universities like Florida Polytechnic are the main competitors of this industry. To differentiate themselves and be competitive in the industry HDAS is working with NASA engineers to design and develop an innovative articulating deployment system, whereas competitors have been developing deployment methods that lack articulation capabilities. The passive capabilities of this articulation also allows for our product to be utilized by private communications companies or other purchasers who would benefit from CubeSat missions without requiring extensive knowledge of operation.
Proof of Concept
HDAS’s proof of concept was to verify and validate that full 1-meter deployment of the solar array from the CubeSat via a scissor-lift boom is feasible, structurally stable, and rigid enough to allow articulation of the solar array. Computer Aided Design (CAD) software was used to design the boom and then analyze the modal frequencies and buckling factors when the boom is fully compressed, half way deployed, and fully deployed. The analysis results concluded that the designed concept will deploy the stowed solar array, with a mass of 550 grams, without failure due to buckling or modal frequency. A motion study was also conducted to confirm the system fits within the compact volume constraints of a CubeSat. Using the work-energy method, the total power consumed by the whole system was determined so that an appropriate motor may be chosen. After selecting the boom design, the articulation system, consisting of shape memory alloy springs to passively track the sun, can be implemented into a complete system design.
The product design specification outlines the design inputs of the small satellite solar array deployment and articulation system. The intended use of this system is to remotely deploy a solar array one meter from a LISA-T satellite, then articulate a solar array ±45˚ in 3-D space. The articulation is intended to autonomously track a single light source (i.e. the sun) and position the solar array perpendicular to that light source to maximize energy generation. Maximizing the power generation can solve the power constraint to small satellite systems. This system will also be used in low-Earth orbit or less than 2000 km. From the testing environment from Earth, the system will be calibrated to match the parameters in the orbit. From this product, it can be used for space application such as earth observation and communications at a low cost.
The fabrication process includes members and pins for the scissor lift boom, different variation of mounts, bracket, screws, rails, spacers, rollers, and nuts. These parts will go into the CubeSat frame along with servo motors. The machine fabricated parts are produced by the manufacturing shop at UNR, using the drawings provided to ensure that they meet the needed specifications. The machined members will be pinned and clipped into place to ensure that they have a secure and smooth connection at each joint. After the scissor lift members have been assembled, then the bottom and top plate assemblies will be attached. Once the manufactured parts have been assembled, the servos and other electrical components will be integrated into the product and wired together. After basic assembly of the mechanical and electrical parts, the product will be tested to find any errors in assembly that need to be addressed before full scale, final runs.
Testing and Results
Team High Desert Aerospace Systems designed a Solar-Array Deployment and Articulation System (SADAS-42) that deploys a solar array one meter away from the spacecraft and then begins articulating the array to optimize its position toward the sun. The articulation and deployment systems were both tested eight times after the prototype was constructed to validate its operation. In order to test our deployment, we timed how long it took to extend the scissor members to full-deployment and confirmed they reached that final state in less than three minutes (this was a stated PDS parameter).
The other tested parameter, articulation, was tested using an LED flashlight to illuminate specific light-dependent resistors (LDR’s) and then used qualitative analysis to judge whether a perpendicular position to the light source was achieved. Initially, this testing revealed a coding issue where our servo motors (which operated the array positioner) got stuck in a loop when it reached a singularity position. This was solved by increasing the singularity bounds to mitigate the risk of the array bouncing between singularity positions. This problem was further alleviated by completing a full-rotation away from the singularity before continuing to articulate. Overall, the main issues in our assembly were from this coding so they were solved from iterative testing. The articulation system passed our analysis, and since this subsystem is highly programmable, parameters like speed, angle of rotation, and delay can be constantly changed so there is not a direct state that can be tested. Our LDR’s consistently supplied valid data on incident light brightness so we encountered no problems in optimizing array position. This subsystem is thus validated.
Our system was successful in optimizing the array’s position one meter away from the host spacecraft. This success fulfilled the requirements outlined by NASA in our product design specification (PDS) documentation. The automation inherent to our system would be a great solution to private industry or graduate students who are conducting low-earth orbit research and who do not want to be encumbered with designing their own power-generation systems.
Prototype Video (Google Drive Link):
Meet the Team
Ngan Nguyen was born in Biên Hòa, Vietnam, but was raised in Sparks, Nevada. He is a senior at the University of Nevada, Reno and will graduate in May 2018 with a Bachelor of Science in Mechanical Engineering. Throughout his college career, he performed multiple hands-on group projects and developed software skills such as CAD modeling and analysis in SolidWorks and programming with MATLAB. After graduation, Ngan intends to work in the renewable energy or robotics industries.
Reed Parkhurst was born and raised a stone’s throw from UNR in Sparks, Nevada. He is on track to graduate in May 2018 from the university, and plans to work in industry for a few years after graduation until starting his own engineering company. Through his coursework at the university he has been involved in a variety of hands-on projects, but the most extensive so far has been his capstone project of developing an articulated deployment plate for use by NASA. In order to develop this project, Reed has had to draw from his knowledge of subject matter varying from properties of materials and mechanical component design to thermal considerations of circuitry to be implemented.
Logan Williams is a senior Mechanical Engineering student at UNR in Reno, Nevada where he was born and raised. His most difficult engineering challenge has been coding in his MATLAB courses for projects which require extensive inputs and commands for proper simulation. At UNR he has developed skills in coding, 3-D design, circuitry, as well as advanced physics and mathematics. Logan has utilized his engineering knowledge and helped his father design and renovate multiple rooms in his house including the kitchen, computer room, garage, and bedrooms by installing cabinets, countertops and flooring, and constructing bedframes and desks. Prior to graduating, Logan plans to get his engineering intern license and hopefully an internship to match. After graduation, Logan is hoping to get a job which will support him continuing his education in pursuit of a Master’s Degree in Mechanical Engineering, and hopes to pursue a welding certification and minor in Mathematics and Civil Engineering as well.
Jared Means was born in Ogden, Utah and moved to Sparks, Nevada at the age of 12. In addition to attending the University of Nevada, he has currently worked for a local Aerospace/DOD corporation as a Mechanical Engineering Intern for the past two years. During this internship, he has developed skills working with CAD modeling, GD&T drawings, FEA modeling/analysis and standard engineering practices. Jared is currently in the accelerated MS/BS program and will graduate in May 2018 with a Bachelor’s of Science in Mechanical Engineering and a minor in Mathematics, then again in May 2019 with a Master’s of Science in Mechanical Engineering. After graduation he plans on continuing to work in the Aerospace/DOD industry.
David Gaddis was born and raised in Reno and is set to receive his Bachelor of Science in Mechanical Engineering with a minor in Mathematics in May 2018. David expressed an early interest in Engineering when he was elected the President of his high school robotics team during his senior year. This passion grew in college as he attained a leadership role in the Nevada Robotics Society, contributed designs and structural analysis to the Human Powered Vehicle Club, and served as a Research and Development Engineering Intern for two years with the Hamilton Company. After graduation, David plans on pursuing freelance engineering-design work and continue his studying into maritime robotics. David’s experience with mechanical design will prove instrumental in creating complex and functional systems such as the HDAS deployable boom.
There were multiple influencers to the success of our product. John Carr Ph.D., Director of Electrical Systems for the Marshall Space Flight Center, who through his weekly teleconferences, offered us invaluable knowledge about satellites and space systems. Yan Wang Ph.D., Assistant Professor of Heat Transfer, aided us in constructing thermal models of our preliminary articulation system. Saul Opie Ph.D., aided us in mechanical design. Finally, the machine shop work provided by Brian Nagy was absolutely essential because we would not have had a project to present without him.