Power Systems for Small Satellites

Abstract

The satellite power system is a vital component of all satellites and involves a number of parts. All of these parts play an important role in the success or failure of a small satellite mission. Since electrical power systems have been around since the beginning of the space age, and their function has been well established, this part of a satellite design for this reason might be taken for granted. It also may be outside the expertise of cubesat builders with limited experience. This is a serious problem, as many telecommunications systems, on the ground or in space, often fail due to a power failure. This can be not only because the power generation or storage system fails but for other seemingly mundane factor such as a simple short in a wiring system that causes a satellite to fail due to a lack of critical power supply or even an electrical fire that destroys the entire satellite. Other sources of failure can come from as simple a problem as the leads from solar cells or photovoltaic cells failing due to contamination or oxidation that creates an overall power failure for a satellite. Experience over the years have confirmed the need to carefully design, manufacture, and test all aspects of a satellite’s electrical power system in terms of safety, resilience, and lifetime performance. This important work is often overlooked or minimized in cubesat projects. This chapter discusses all aspects of electrical power generation, an electrical power distribution system, power storage, and effective design of an electrical power system for all types of satellites that range from a femtosat (10 to 100 grams), a picosat (100 grams to 1 kg), a nanosat (from 1 kg to 10 kg) that includes cubesats, a microsat (from 10 kg to 100 kg), and a minisat (from 100 kg up to 500 kg in some definitions and from 100 to 1000 kg in others). The point is that power systems can command a good deal of the mass and volume of a satellite regardless of its size, and thus the power-to-mass ratio is important in satellites designs and especially so in the case of small satellites. Different approaches to power can thus be taken for different types of small satellites depending on their mission, lifetime requirements, and overall mass and volume. Finally, this chapter seeks to provide information developed by NASA and other objective sources about the suppliers of critical elements of an electrical power system for small satellites and especially with regard to solar power cells and power storage units.