Organização sistêmica para concepção de carga útil em CubeSat usando supercapacitor

Abstract

Recently, the Universidade Federal de Minas Gerais (UFMG) initiated a CubeSat project, a satellite standard with size and mass requirements, with the purpose of conducting technological demonstrations, including the evaluation of a supercapacitive cell applied to low-power electronics developed at the university, as well as promoting specialized workforce training. Therefore, this work consists of systematically organizing the design of the payload of a CubeSat using a supercapacitor. In the context of this work, the CubeSat’s payload is composed of a flexible solid electrolyte supercapacitive cell applied to power supply in low-power electronics, the System to Automatic Acquire of Electrical Signals from characterization Supercapacitors (SAAESSC) and its respective software, all developed internally at UFMG. For this design, it is necessary to understand the working conditions of the CubeSat in low Earth orbit (LEO), verify which tests are performed on CubeSats for payload validation, verify the tests performed on supercapacitors for electrical characterization, propose and validate a temperature test protocol, carry out the validation tests of SAAESSC, start the tests of the supercapacitive cell, and promote communication and integration among the involved laboratories. The tested supercapacitive cell is composed of: gel polymer electrolyte formed by POLY(Ionic Liquid)-PIL = [A2M2Am][TFSI] and the Ionic Liquid- IL [EPPy][TFSI], with reduced graphene oxide (r-GO) electrode with active material. It was chosen considering some electrical characteristics, such as specific capacitance, energy density and power density, as well as physical characteristics like electrolyte volatility and viscosity. The initial temperature test was conducted on the supercapacitive cell sample and consisted of galvanostatic cycling and charge and self-discharge, first at room temperature and later with gradual temperature increase. Two rounds of the suggested protocol were carried out, and the results showed that the sample remained operational after the temperature increase, presenting better results at higher temperatures. However, it suffered degradation from one test round to another. Aiming to promote electrical tests of the supercapacitor, SAAESSC was designed to perform galvanostatic cycling and charge and self-discharge tests, whose collected data are used to characterize the device’s electrical parameters and calculate its respective equivalent electrical circuit. The equipment proved to be promising, as, when comparing the results obtained by it with the results obtained by the potentiostat/galvanostat multichannel VMP3 equipment from the BioLogic brand, an error percentage of 0,23% was obtained, with a standard deviation very close to zero. In this work, fundamental improvements were identified to be redesigned in SAAESSC and the tested supercapacitive cell for application in CubeSat.