ABSTRACT
Introduction ............................................................................................................ 593 Background ............................................................................................................ 594 Hubble’s Troubles beyond Optics: Electronics ...................................................... 595 Space Environment ................................................................................................ 596
Atomic Oxygen ............................................................................................. 596 Vacuum Operation ........................................................................................ 597
Spacecraft Effects .................................................................................................. 597 Thermal ......................................................................................................... 597
High Temperature ............................................................................. 597 Low Temperature .............................................................................. 597 Temperature Cycle ............................................................................ 598
Charging........................................................................................................ 598 Meteoroids/Orbital Debris ............................................................................ 599 Solar Environment ........................................................................................ 599 Geomagnetic Field ........................................................................................ 599
Generic Electrical System Description ..................................................................600 Power ..................................................................................................................... 601 Electronics in Space History ..................................................................................602 Types of Spacecraft Electric Power Sources ..........................................................604 Commercial versus Space-Grade Components ......................................................605 Wiring Failures .......................................................................................................605 Conclusion: Development of the Transistor-the Technological Perfect Storm ...605 References ..............................................................................................................607
Three main concerns of operating in the environment of space on electrical systems are vacuum, thermal, and radiation effects. In addition, other impacts from operating
in the low-to zero-gravity environment and particular constraints to designs will be discussed in this chapter. The space environment basically does not change; rather, our approach to performance in the space environment has changed over the years. Therefore, beyond understanding the space environmental impacts there are discussions of the evolution of electrical systems elements and how to track and understand pedigrees and dates. It is important to understand the dramatic difference between electric systems deployed on Earth or near Earth where servicing is a built-in factor compared with space applications. There is, with the exception of the euphemistic term “servicing” of Hubble Space Telescope (HST), limited to no servicing of systems, which couples with the incredible cost of placing useable satellites, manned missions, space station, and launch vehicles into space. This pairing drives distinct differences in the design of systems that are unrecoverable and irreparable. For many critical systems the equipment is redundant; that is, there are two (or more) of each system, providing backup. Where full redundancy is impractical, other techniques are used, such as paralleled converters, fused bus capacitors, majority voting, and so forth. Beyond redundancy, electrical systems for space have relied on heritage systems and derating. Heritage refers to systems and components that have been own before, and derating refers to driving systems well within their performance range. In order to understand the electrical systems, a description of the various components of these systems is also included and discussed in relationship to variety of impacts of the space environment. Additionally, an understanding of the various power systems is included in this chapter to emphasize its necessity and vulnerability-the Achilles heel. The electrical system is the lifeline of all electromechanical space systems. Although failures in space are covered in separate chapters, a discussion of the electrical failures and anomalies as they relate electronics in the space environment are discussed as a representative case study in a discussion of the Hubble Space Telescope.
