For experts only, this volume is actually a textbook and utterly beyond the grasp of the average reader. In discussing space flight, the author keeps entirely to physics and does not venture into astronaut training, space foods and assorted biological data. The only thing relatedly like a story is a final hypothetical flight to a star 100 light years distant. The author's main interest here, as in most of the book, is in the dynamics propulsion. For this trip on the day after the day after tomorrow, his ship is equipped with a photon propulsion engine which pushes the ship to over 99.9% of the speed of light. Because at that speed time and distance dilate, the 200 light years round-trip distance would take 210 earth years of time but only 34 shipboard years, which is comforting...Aside from the spiritual adventure of interplanetary and interstellar flight, the author thinks that our necessary subordinate inventions for the flights will repay all investment.