One of the Grand Old Men of space travel restates and amplifies many of his basic principles. Nothing is too small or complex for his attention, whether it is sewing up a spaceman's sleeves or locating an observatory on an asteroid. Oberth speculates alike on the best angle for firing a rocket from earth and on the precise thickness of a space mirror which incidentally might have a commercial use in melting the icebergs that slow up ship transport. He is knowledgeable about car design for motoring on the moon, and gives pointers on establishing the medical and mental fitness of would-be explorers. Oberth's exactitude is sometimes formidable, and the mathematical supports to his views in the appendix are tough going for the uninitiate. But most of the findings read readily, and are directed toward that audience of afficionados.