Coryn Bailer-Jones’ The Physics of Interstellar Travel fills a need which has become apparent only in the last twenty years. Indeed, going back to the turn of the century, one would find the idea of traveling to another star discussed only in relatively isolated pockets, often presented at the tail end of conferences devoted to other astronautical topics. Papers, though, were being written at an increased rate, building on early work begun in the 1950s through the efforts of luminaries such as Les Shepherd and Eugen Sänger and continuing into the era of Robert Forward. By the year 2000, a number of mission designs had been created, still very much on the back burner but of high interest to specialists.
In today’s landscape, interstellar travel has become a vibrant topic. The wave of interest that energized the field incorporated high-visibility projects like NASA’s 100 Year Starship and in 2016, the emergence of the Breakthrough Starshot Initiative, which focused directly on the design of a probe that could reach a nearby star, presumably Proxima Centauri, within a human lifetime. Public interest in starflight has likewise been galvanized by the fast pace of exoplanet discovery, and growing attention to the question of studying such worlds through actual missions. Cementing the enthusiasm has been a stream of Hollywood depictions that offered viewers enticing imagery of such journeys.
The surge in papers discussing interstellar flight has exposed the lack of a college- and graduate-level treatment, a textbook wholly devoted to this topic. The Physics of Interstellar Travel meets that need with the precision of a key clicking home in a lock. It is a thoroughly researched analysis that presents travel to a star within the context of known physics, validating the perception that such journeys are within the realm of future engineering. Early chapters on orbital mechanics and the mathematics of rocketry illustrate the fact that each section can stand on its own in specialized classes at higher levels, while the quantitative analysis offered here will be of use to any student who has mastered college physics and is ready for the next educational step.
Although Bailer-Jones accepts the idea that star travel violates no physical laws, he is careful to acknowledge the challenges that emerge and the direction of future work that will eventually meet them. The principles of rocketry lead him to present fusion and beamed lightsail concepts as the likeliest paths forward, with the clarity provided by mathematical analysis applied to options including ion engines and antimatter. The nature of the interstellar medium is considered in terms of dust mitigation as well as the possibility of ramjet solutions. Communications and navigation receive thorough treatment but so do the essentials of orbital mechanics and relativistic motion.
The Physics of Interstellar Travel is, in short, a comprehensive extension of current textbooks in astronautics into the realm of missions once thought to be impossible. This book’s mathematical rigor should clarify for rising students the realization that steps we take today can result in practical outcomes, with the goal of reaching another star conceivable by the end of this century. Bailer-Jones advocates a step-by-step approach in which precursor work always tests new ideas to avoid the problem of future missions making earlier ones obsolete before they have reached their target. Where science and engineering have not yet taken us, this textbook illustrates the direction of steps forward, aiding the community in the construction of the needed roadmap.
