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Electrical Power

Scope and Description

This topic page covers testing of spacecraft electrical power systems. Smallsat power subsystems typically include power management and distribution (PMAD) electronics, chemical batteries for energy storage, and solar arrays for power generation. Because smallsat power systems are typically single string and power cycling of other subsystems (or the entire spacecraft) is a useful way to clear faults, electrical power system reliability - and therefore testing - is an important driver of overall spacecraft reliability. In addition, energy storage in this subsystem means that it poses a risk to other space systems involved in the launch and deployment process (e.g., the ISS or the primary payload on a launch vehicle). This risk to other systems usually imposes additional testing requirements.

Resources under this topic area are primarily articles and whitepapers describing power system testing of small satellite systems. Note that more general but relevant resources and guidance regarding electronics testing is available in topic pages immediately under "Integration and Test" in this knowledge base.

Best Practices and Lessons Learned

  • Battery testing, both at the cell and pack-levels, is an inherently time-consuming process involving many charge/discharge cycles. Budget significant schedule for this process and, if possible, have spare cells or packs available to minimize the schedule impact of failures that cause excessive stress or damage to the battery cells.
  • Test for startup from a tumble, ideally with worst case axis and rate of rotation. Depending on your spacecraft's inertial properties and the specific of the deployment or separation mechanism, the spacecraft could initially start up with significant rotation relative to the Sun. Alternatively, a tumble could occur if there is an attitude control system malfunction or if the spacecraft shuts down for an extended period and accumulates angular rate from perturbation torques. The resulting dynamics of solar array input power, combined with the bandwidths of digital and analog control loops and boot-up time in the PMAD electronics can be challenging to fully capture with analysis.
  • A thermal camera is a relatively inexpensive piece of test equipment that can provide significant value when identifying workmanship flaws and component failures in power electronics. In many cases, a component that fails during power electronics testing results in localized heating that does not match up with reference thermal images of the same system.
  • Use heavy gauge, twisted cables to connect test equipment to power systems under test. Test cabling can be labor intensive to produce. Cost tends to be concentrated in the connectors and labor, so it is typically worth the marginal increase in cost to use heavier gauges. The heavy gauge will support longer cables that can be reused on multiple tests and will make testing easier to set up. The reduced resistance will also prevent the series resistance of cabling from influencing testing, which is particularly likely when verifying overcurrent protection functions on batteries and PMAD electronics.

Resources

This thesis provides a description of the functional testing of the MIniature Student saTellite (MIST) ... cubesat electrical power system (EPS). This includes the development of custom, low-cost test equipment, test procedures, and results.

This document is an Interface Definition Document (IDD) outlining the minimum requirements necessary ... to integrate with the NanoRacks CubeSat Deployer (NRCSD) system. Battery and power system inhibit/protection requirements are outlined and provide valuable input for EPS designers hoping to support ISS deployment.

This paper provides an overview of the electronic power system (EPS) on the KySat-1 and KySat-2 1U cubesats. ... Detailed information on how to design and develop an EPS for use in smallsats is thoroughly discussed, with a particular focus on a novel distributed power system architecture.

This introductory document outlines the basic concepts and processes involved in developing cubesats. ... This section, titled "Battery Report", discusses the required battery specs that need to be documented and provided to the mission integrator.

Article
Zachary Cameron et al.

This article discusses the additional testing and certification processes that smallsats need to undergo ... when the electrical power system (EPS) uses Lithium-ion batteries and is being deployed from the International Space Station (ISS). These types of batteries pose different hazards typically from overcharging, short-circuiting, and high temperatures.

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