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Electrical Power

Scope and Description

This topic page covers the design of electrical power subsystems (EPSs) for small satellites. This includes design of the subsystem components, selection of commercial off-the-shelf (COTS) components, and integrated design/sizing of the complete subsystem. 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 design is an important driver of overall spacecraft reliability.

Resources in this topic area are primarily website databases of smallsat COTS components and book chapters on satellite power system design.

Best Practices and Lessons Learned

  • Consider launch and deployment related requirements early in the design process. The function and fault tolerance of inhibits in your power electronics and battery test requirements can vary significantly by launch provider and over time. Work with your launch provider - or any potential launch providers - to solidify these requirements (or at least conservatively bound them) early on. Failure to meet these requirements can cause missed flight opportunities and last minute delays in your project that are hard to recover from.
  • If your smallsat will be deployed from the ISS and have a battery capacity greater and 80 Whr, consider physically and thermally separating the energy storage system into packs with less than 40 Whr of capacity. This may allow you to avoid additional battery fault protection and testing requirements. Work closely with your launch provider (or any potential launch providers) to confirm that this is a valid option and clarify any conditions for reduced requirements.
  • Your PMAD electronics should have a watchdog for the flight computer and for the PMAD electronics controller. If the EPS watchdog or flight computer is not regularly "pet" then a reset should be initiated to clear any faults.
  • Consider implementing a simple, bi-level reset signal from your uplink receiver directly to your PMAD electronics to provide a backup reset mechanism in addition to any watchdogs.
  • Design for significant energy balance margin in your solar arrays and batteries. This will improve fault recovery performance of uncontrolled satellites in worst-case power generation attitudes and/or beta angles. In addition, this will improve orbit flexibility and therefore your ability to take advantage of alternate launch opportunities.

Resources

This annual state-of-the-art report from NASA provides an assessment of the current state of the smallsat ... industry, guidance, and best practices for all aspects of the smallsat development life-cycle. This section, titled "Power", provides a survey of the state-of-the-art offerings for COTS EPS components.

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 site provides cubesat requirements, guidance, and available product offerings related to electrical ... power systems (EPS). Each EPS listed has a direct link to the spec sheet, CAD model, and purchase information through SatSearch.

Book
Joseph N. Pelton et al.

This book provides an overview of the smallsat industry and covers spacecraft technology, applications ... and services, launch procurement, and a number of other topics. In this section, titled "Power Systems for Small Satellites", all aspects of electrical power generation, distribution, storage, and architectural design for smallsats are discussed.

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.

Book
George Sebestyen et al.

This book chapter, titled "Electric Power Subsystem Design", provides a concise process for designing ... the electrical power subsystem (EPS) for a low Earth orbiting spacecraft. The author asserts that the EPS is often considerably under-designed and unable to meet the power requirements for smallsats, and goes on to recommend techniques to ensure sufficient orbit average power (OAP) and battery capacity margin.

Book
James R Wertz et al.

SMAD is a practical handbook for space mission engineering covering all aspects of a space system - from ... orbit and constellation design to operations. This reference is valuable as both an introductory text and a reference. This sub-section, titled "Power", discusses the design and function of the electrical power subsystem (EPS).

This article provides a comprehensive review of past, present, and future smallsat battery technologies. ... Specific battery types, characteristics, and requirements are detailed with examples and results from testing and analysis.

Website
NASA and AFRL

SPOON is an online database of smallsat components such as payloads, flight processors, antennas, propulsion ... systems, equipment for ground stations, and power systems.

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