Table of Contents
Team Vision for System-Level Design Phase
Based on the understanding of the project developed in the problem definition phase, this page details the process used to come to an overall systems design.
- System requirements were used to generate a functional decomposition. This document lists all tasks to be performed by the system.
- Ideas for each functional requirement were brainstormed to generate system concepts.
- A set of selection criteria were developed to evaluate the utility of each concept.
- Feasibility analysis was performed to evaluate whether each system could be created.
- A final system concept was chosen to best achieve the system requirements set fourth in phase one.
Above is the functional decomposition of what is necessary for the deliverable of P16102 to actually do. Elements outlined in red were further developed through the morphological chart
The first type of major functions dealt with Constraining the Subsystems within the structure of the CubeSat. This really dealt with housing the internal circuitry and also stowing the solar panels during transit, integration and launch.
The second type of major functions dealt with increasing solar energy or increasing the area time effects. Of this, deploying the array was the most decomposed about the unfolding, extending and maintaining the structure, and following the sun was included at the first revision due to the original customer requirement.
Finally, the last set of requirements and functions identified were focused on meeting launch requirements. With this, P16102's deliverable would need to meet the cost needs, CSLI requirements and space environment requirements to be successful at the prototype stage.
This discussion started the process of reviewing engineering and customer requirements.
Morphological ChartMorph Chart PDF
During analysis, we identified that consistently the two driving choices were methods of pivot and methods of folding. From this, all other decisions made would be affected from that decision and nearly everything else identified on the pugh chart could be easily adapted. By choosing this from these two decisions outwards, we reduced the size of the trade-space very quickly and efficiently.
Due to the fact that may of the other functional requirements could be accomplished by interchangeable subsystems, the concept selection process for the overall system was focused primarily on the folding structure of the CubeSat. Many separate concepts were developed during the brainstorming phase, however the following seven were chosen for to move on to the pugh chart:
|Single Pivot 2x1 (click for animation)|
|Fan Fold (click for animation)|
|2 Panels w/ Axel 2x2 (click for animation)|
|Single Stationary 2x1|
These concepts were chosen because they span a wide variety of deployment possibilities, as well as a broad range of complexity.
Selection CriteriaTo differentiate between each of the concepts, several metrics were chosen as selection criteria. These metrics were then weighted based largely on their relationships with key customer requirements using the house of quality.
Feasibility: Prototyping, Analysis, SimulationBefore evaluating each of the selected concepts, some basic engineering analysis was performed to ensure that each of the designs would be feasible.
To this point, we have been operating under the assumption that the CubeSat will experience a temperature range from -40 to 40 degrees Celsius, based on knowledge of previous CubeSat experiences. Since our design will incorporate deployable solar panels, however, it will allow for more exposure to solar radiation relative to the area on the CubeSat that will radiate out heat. This may cause our CubeSat to absorb more heat than it can radiate and go above the predicted 40 degrees Celsius threshold. To determine if this is a real possibility, a theoretical model was created using reasonable material properties and a worst case scenario where the CubeSat reaches thermal equilibrium with the maximum area exposed to the sun. This analysis yielded the result that none of our design concepts would push the CubeSat temperature above 33 degrees Celsius, comfortably within the 40 degree limit. With this in mind, we do not have to limit our designs on the basis of radiative ability.
Area Time/Orbit SimulatorThis tool simulates a vehicle placed in an orbit around the earth at a given altitude and determines some properties of the orbit, time for the solar panels to hit the sun and gather energy.
Mass of Solar PanelsTo determine the feasibility of each of the designs, the approximate weight of all of the solar panels must be known, so a remaining mass margin can be calculated for all of the support structure as well as any actuation mechanisms. Based on CubeSat specific solar panels already on the market, the typical mass of a single 10cm face solar panel is in the range of 29-50 grams.  
Pugh ChartsUsing these selection criteria, pugh charts were generated to chose the most beneficial concept design. Several of the concepts were chosen as a datum, and then compared to each of the remaining systems. Based on the weights assigned to each of the selection criteria, a weighted sum was used to choose the best design.
After careful consideration of each concept idea, as well as pugh chart analysis, two similar subsystems showed a strong set of advantages.
The exploded 2x1 and the single stationary systems both outperformed each of the other concepts. The selection criteria that made these solutions stand out were caused primarily by the simplicity of the systems, as well as their low volume and mass.
Selected Concept Deployments
These two final concepts are both characterized by two opposite panels deploying a single face, with three panels on stationary faces. The difference between the two designs is in the integration of the panel in the structure. In the "exploded" concept the deploying panels serve as structural support for the frame during launch, after launch, the two frame panels are separated and deployed. In the "stationary" design, the two deploying panels are attached to the outer faces of the frame, and they deploy while leaving the frame shape unchanged.
The final concept chosen does not include deployed panel articulation. While the articulating version of these systems were able to generate roughly 40% more power, the decision was made to stick with the simpler system in favor of increased reliability, as well as decreased mass and volume. These metrics all strongly affect the final value of the system and are likely more important to overall mission success.
Final System Functional Decomposition
BenchmarkingInvestigation into possible alternatives to custom design yielded one main manufacturer capable of achieving the customer's objectives. Clyde-Space is a supplier of small and micro spacecraft systems, and is the world's leading CubeSat vendor.  Currently Clyde-Space offers both a 1u CubeSat skeleton structure, and also a 1u CubeSat deployable solar array. They are currently priced at $925 for the structure and $5,650 for the deployable array (two full faces). This is out of the customers budget therefore a custom design must be made. Below is both the cubesat structure and deployable panel offered by Clyde-Space. Example of Clyde Space Deployment  
Clyde-Space does not currently offer articulation in a 1u deployable solar array. Researching for possible solutions in academia yielded nothing. Articulation is not currently or has not been done for a 1u CubeSat. CalPoly has constructed a 3u articulating solar array.
Cajun Advanced Picosatellite ExperimentBelow is an example of deployment from a 1u CubeSat. It shows the structure as rigid which is required for inside the PPOD but after launch it is not required to be rigid. CAPE2 claims to be the first 1U CubeSat to use deployable solar panels. They custom built the spring hinge and used fishing line running through a resistance coil to deploy the panels. 
Xatcobeo Spanish CubeSatA solar array deployment system was designed and simulated by the Xatcobeo project team. The team confounded of students from the University of Vigo and the INTA (Spain National Institute for Aerospace Technology). The solar array deployment was designed and simulated but not built. In the research article it was concluded that more than one panel that unfolds will induce to much mass not allowing for symmetric deployment. However for there simulation they used this double fold to show the strength properties of the spring and deployment mechanism. In the figure below the deployment mechanism is portrayed. 
Functional Test PlanningTo evaluate the success of our design, several tests will be performed both on the physical structure and on computer aided design models to ensure overall system performance.
- Deployment: Simple functional testing will be performed to ensure the overall deployment mechanism works as intended. The frame will be suspended off the ground in such a way that the deployment of the array will not need to overcome the force of gravity. Using a battery power source, the deployment mechanism will be activated to extend the panels.
- Vibration: To evaluate the system survivability under typical launch conditions, we will work with P16103 to develop and perform a functional vibration test based on typical launch vehicle vibration profiles.
- Inertial Change: To ensure that the deployment of the panels does not significantly alter the center of gravity of the CubeSat, CAD modeling software will be used to calculate the center of gravity of the deployed structure.
- Thermal Simulation: To evaluate the ability of the CubeSat to maintain a safe operating temperature, computer simulation analysis will be performed on the structure to estimate the operating temperature of the system under typical orbital conditions.
Advocate StructureDue to the small size of our group, we will often find ourselves in situations where one person will have to work on multiple areas of the project in order to meet the deliverables of a certain phase. Because of this, no one on the team will rigidly specialize in one area of the project. That being said, we still feel it is important for each section of the project to have someone looking out for it specifically and making sure it progresses as needed. To make sure all parts of the project are “owned” without sacrificing the flexibility our small size mandates, we have developed an advocacy structure. In this structure, each group member is assigned to be an advocate of a portion of the design. The advocate is responsible for making sure the needs of their portion are taken into account but may still work on other portions and receive help on their portion from other members. The team advocacy breakdown is as follows:
- Integration: Anthony
- Deployable Structure: Paul
- CubeSat Structure: Robert
- Deployment Mechanism:Tristan
Phase III Deliverables
- Review SDR Action Items, Update Requirements, and
Identify Subsystem Resources
- Begin Subsystem Design Layout
- Identify All Critical to Performance Interfaces
- Analyze Possible Alternative Designs
- Begin to Develop a CAD Package with Guides
- Follow Labeling Scheme from the Nomenclature Page
- Relate All Subsystem Component Specs to Parent Requirements.
- Begin Subsystem Design Layout
- Proof of Concept
- Analysis and Simulation
- Deployment - Simulation
- Vibration - Analysis and Simulation
- Inertial Concept - Analysis
- Thermal Environment - Simulation
- Possibly Create a Full Launch Cycle Simulation - Thermal, and Mechanical Stress Simulation
- Analysis and Simulation
MSD 1 Deliverable Planning
MSD II GoalsBy the end of MSD II, we will have produced a CubeSat structure with at lease one deployable solar panel integrated into the CubeSat, two if possible. The array(s) will have locking and deployment mechanisms. The deployment mechanism will have been tested to demonstrate deployment reliability. The entire structure will have undergone thoroughly documented vibration testing in conjunction with P16103. The CubeSat design will be completely documented with finalized CAD models and a B.O.M. Our plan for the remainder of MSD I supports our ability to complete these deliverables during MSD II.
(individual 3-week plan template for this).
- ↑ Clyde-Space Solar Panel Example, Web, 2015
- ↑ ISIS Solar Panel Example, Web, 2015
- ↑ Clyde-Space description, Web, tictoc, 2015
- ↑ Clyde-Space CubeSat Shop where components can be purchased, Web, tictoc, 2015
- ↑ Clyde Space Example, Web, tictoc, 2015
- ↑ Presentation on the constructed articulating array, Web, CalPoly.edu, 2013
- ↑ Mechanical Design of CAPE2 - the Second CubeSat being designed under the Cajun Advanced Picosatellite Experiment, Web, researchgate.org, By: A. Bajpayee, 2015
- ↑ Xatcobeo: Small Mechanisms for CubeSat Satellites - Antenna and Solar Array Deployment , Web, researchgate.org, By: J. Plaza, J. Vilan, F. Agelet, J. Mancheno, M. Estevez, C. Fernandez, F. Ares, 2010
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