434 Power system requirements impact  the entire design of XSAS. While most CubeSat po wer requirements  are limited to 5 W, XSAS shall supply 20 W of aver age continuous power during its sunlit orbit. As a  result, its array needs to contain enough solar panels with highly efficient solar cells to produce this  power. Additionally, the deployment mechanisms must be small enough to fit the required number of panels within the solar arrays 1U stowed volume budget.  The release mechanism is required to be redundant, r obust, and reliable. As an active system, testing  and verification is vital to the performance validati on. Therefore, for testing purposes, the release  mechanism shall be simple, inexpensive, and repeatable with a 10 minutes maximum reset time.    The hinge and deployment system must deploy the array passively, control the deployment rate, and lock the array into its open configuration. After initial estimates the entire hinge syst em is required to have less  than a 3-mm height when folded in order to have enough vertical space for 16 solar panels. Hinge width  and length also need to be minimized to ensure maximum available surface area, while still providing a  reliable connection between panels. Finally, the perfo rmance of the array during deployment must be  passively controlled at all times to eliminate shock on the structure and payload. This means additional  mechanisms must be integrated to passively control the array’s deployment orientation and rate.    Note the possibility of gravity gradient stabilization is an inherent quality of the deployed XSAS geometry in LEO. To take full advantage of this unique quality,  the system’s passive pointing accuracy must be  considered in the structural design, mass, and vo lume budget. Since passive pointing accuracy is  controlled by the center of gravity of the deployed system, suitable volume must be allotted for ballast or additional functional mass at the top of the array. Mission specific requirements may have a major impact  on the application of this design and shall be considered when sizing the ballast hardware.   Fabrication Requirements

Fabrication requirements control the cost budget and manufacturing time of XSAS. The following list details the top level sub-system requirements and is followed by explanations of their application.  • XSAS shall include all commercial off-the-shelf (COTS) components and materials  • Any fabrication shall be done in house using available student accessible machinery  • Fabrication of the final XSAS prototype sha ll be completed and tested within 3.5 months    The purpose of these requirements is to restrict the cost of manuf acturing a complete XSAS system. By  limiting the mechanisms to COTS parts and materials, engineers can focus on the custom and creative integration of these parts. Addi tionally, mechanisms and components can be rapidly prototyped for testing  and production. Lead times of custom parts will not impact the manufacturing time of any XSAS subsystem.  

Simulations 

Analytical simulations and trade studies were requi red to determine the quantitative requirements and  behavior of the XSAS solar array and gravity gradient sy stem. The solar array was sized based on a trade  study between two types of solar cells with avera ge on orbit power losses. The gravity gradient analysis  was also completed using simplified disturban ce models and the projected geometry and mass  distribution of the deployed XSAS and payload. The following sections describe the details of each trade study.  Solar Cell Selection

According to volume constrains, the XSAS array c an have as many as 16 panels. To determine the  maximum power capacity for this array, a trade study  was completed comparing Spectrolab Triangular  Advanced Solar Cells (TASC) and Emcore 2nd Generation Triple Junction (BTJ) cells. The most obvious  difference is the efficiency and price of each cell. An array composed of TASC cells is half the cost of a BTJ array with an efficiency of 27±3% and 28.5% [10] [11], respectively. Immediately, the additional cost  NASA/CP-2010-216272