The size of EQUiSat’s solar panels is limited by the CubeSat architecture. We have optimized our panels for our own uses by making efficient, affordable panels which produce voltages at our desired range. In accordance with our primary mission of accessibility, it was important for us to minimize the use of pre-built, and often expensive CubeSat components, such as Clyde Space solar panels. We found that by using low-cost, Gallium Arsenide scrap cells from Spectrolab and TrisolX, we can reduce the cost of the solar panels by up to 35 times while maintaining their efficiency in comparison to prebuilt panels. In order to do so, we have developed, and are continuing to iterate, an intuitive fabrication process to make these solar panels from scratch. This process, which has already been utilized by other university satellite groups (such as the University of New Mexico) through the documentation on our website, can help amateurs effectively produce cost-efficient solar panels.
Our chosen LiFePO4 batteries provide a number of unique benefits, and their success in space could expand the power capabilities of small satellites. A123 Systems LiFePO4 cells have high current draw capabilities, up to 30A continuously and 60A pulsed. This eliminates the need for large, electrolytic capacitors, which can be volatile in a vacuum environment. Their chemistry is generally more stable, and as a result, a safer option in comparison to other lithium-ion batteries. Given the problematic phenomenon of thermal runaway, observed in other batteries, the thermal stability of LiFePO4 batteries is promising. LiFePO4 batteries are stronger candidates for use in a space environment where temperatures are likely to increase to extremes near 70 ̊C. The eventual launch of the satellite requires the batteries to be tolerant to physical abuse caused by heavy vibrational loads. Testing conducted in precedent studies has shown that the batteries can be exposed to high magnitude vibrations and other physical stimulation without any noticeable effects to performance. CubeSat requirements also stipulate a mass budget for the satellite, and LiFePO4 batteries offer a lightweight solution for the power system when compared to other available battery options. Additional testing of these batteries is currently being conducted for applications in space at various NASA centers.
The majority of this validation will take place in orbit as we monitor the power budget of our satellite and the health of our system. We will be able to send down this data via our radio to be processed at our ground stations. However, we have already begun the verification of these components on the ground. Through extensive testing in both normal and extreme conditions, we will reduce failure points and validate each component’s success in the space environment. The success of EQUiSat’s power system will set a precedent for the use of this new battery chemistry and the fabrication of space components, opening new opportunities for small satellites. Furthermore, power system failures are among the biggest causes for systemic failure in small satellites. Our efforts to create a reliable, low cost, and simple power system that is capable of handling high power (over the typical high energy) requirements will be extremely beneficial to the CubeSat community.