Book excerpt: Spacecraft Power Technologies is the first comprehensive text devoted to the technologies critical to the development of spacecraft electrical power systems. The science and engineering of solar, chemical, and nuclear systems are fully examined together with the constraints imposed by the space and thermal environments in which the systems must operate. Details of present technology and the history that led to the current state-of-the-art are presented at a level appropriate for the student as a textbook or the practicing engineer as a reference.