Les Shepherd’s 1952 paper “Interstellar Flight” appears in the Journal of the British Interplanetary Society,” a fitting place given Shepherd’s active involvement in the organization. He would, in fact, serve the BIS as its chairman, first succeeding Arthur C. Clarke in that role in 1954, and returning in 1957 and again in 1965 for later terms of office. “Interstellar Flight” is one of those papers that turns people in new directions after they have read it, and we can see the gradual acceptance of travel between the stars as a possibility that does not violate the laws of physics beginning in its pages.

Much less heralded but more widely seen was an adapted version of “Interstellar Flight” that appeared in Science Fiction Plus in April of 1953. The magazine was a revival of Hugo Gernsback’s career as a science fiction publisher that ran for seven issues before its demise in December of the same year. Gernsback’s name was revered in science fiction circles as the founder of Amazing Stories in 1926, and for his later career with Science Wonder Stories and Air Wonder Stories, magazines he would eventually merge before selling his interest entirely in 1936. In contrast to these earlier titles, Science Fiction Plus was printed on slick paper and featured glossy covers, though many of the writers Gernsback used had worked with him in the Amazing Stories days.


Science Fiction Plus was an interesting venue for Shepherd because it exposed his work to an audience that had already encountered science fiction treatments of interstellar concepts like the generation ships he wrote about in the following paragraph:

At first sight the idea of advancing mankind’s frontiers to points requiring hundreds or even thousands of years to reach, might seem hopeless. It cannot indeed be regarded as a particularly satisfactory picture of interstellar exploration. However, regarded in terms of geological eras, centuries or millennia are small intervals, and provided that human life can be sustained in exploring vehicles for long periods, there is no reason why interstellar expansion should not proceed on this basis.

I can envision the Gernsback audience soaking this up, familiar as many of these readers would have been with stories like Robert Heinlein’s “Universe” and Don Wilcox’s “The Voyage that Lasted 600 Years.” The latter, which appeared in Amazing Stories in October of 1940, tells the tale of one Gregory Grimstone, who spends an interstellar voyage in a state of hibernation, but is wakened once every hundred years as the ‘Keeper of Traditions,’ the one contact the crew still has with the Earth left behind many generations before. Here we have the same theme of lost knowledge and a crew gradually losing the meaning of their journey that we find in Heinlein’s Orphans of the Sky and a variety of later tales.

Image: Pioneering physicist Les Shepherd, whose work on interstellar flight has influenced generations of subsequent researchers.

The magnitude of the journey in terms of space and particularly time is well captured in Shepherd’s essay:

The author is not competent to deal with the biological problems of life on an interstellar vehicle undertaking a voyage lasting for a millennium. Obviously they would assume a magnitude quite as great as the engineering problems involved. In the normal way, some thirty generations would be born and would die upon the ship. It would be as though the vessel had set out for its destination under the command of King Canute and arrived with President Truman in control. The original crew would be legendary figures in the minds of those who finally came to the new world. Between them would lie the drama of perhaps ten thousand souls who had been born and had lived and died in an alien world without knowing a natural home.

Now, as to those italics. They’re clearly Gernsback’s, a suspicion natural to anyone familiar with his editorial style. The JBIS paper containing the identical passage has no italics at this point, and it’s clear that Gernsback wanted to drive home the science fictional ‘sense of wonder’ of Shepherd’s remarks with his typesetting. I’m not sure the audience needed the hint. I still find the idea of multiple generations living and dying aboard an interstellar craft to be mind-boggling even when presented in the lean text of the average scientific paper.


Shepherd would go on to discuss worldship issues ranging from population control — for humans and journeying animals — as well as the huge problem of life-support systems in a self-contained world. He saw the only feasible way to make a journey like this would be in a ship of gigantic proportions, and for him, that meant hollowing out ‘a small planetoid,’ one of perhaps a million tons (excluding the weight of propellants and fuel). He believed artificial gravity should be induced by rotating the ship, and he pondered the question of maintaining an atmosphere over the course of ten centuries. On matters of sociology, he said this:

The passage of perhaps thirty generations would pose major problems of a sociological nature. The control of population would be only one of many. Children could only be born according to some prearranged plan, since overpopulation or underpopulation would be disastrous. The community would be subjected to a degree of discipline not maintained in any existing community. This isolated group would need to preserve its civilization, and hand on precious knowledge and culture from generation to generation and even add to the store of science and art, since stagnation would probably be the first step to degradation.

I don’t want to give the impression that Shepherd’s “Interstellar Flight” is solely about worldships, because the original JBIS paper was wide in its scope, examining nuclear fission, fusion and ion propulsion and going into depth on the possibilities of antimatter. Giovanni Vulpetti has pointed out that antimatter had been little studied in terms of propulsion at the time Shepherd wrote, and it was Shepherd who brought the concept out of the realm of science fiction and into the realm of serious physics with this single paper. We owe much to “Interstellar Flight,” published a year before Eugen Sänger’s famous paper on photon rockets, and I think Shepherd was wise to let Gernsback publish a version of it that could reach a broad popular audience.

As for Gernsback, he was canny to bring a serious study of interstellar travel into the pages of his young magazine, although not as successful when it came to story selection. Science fiction historian Mike Ashley has noted a certain archaism in the fiction here because of Gernsback’s reliance on writers from the previous generation. Even so, one Science Fiction Plus story still stands out. It’s Clifford D. Simak’s “Spacebred Generations,” from the August, 1953 issue. As the title implies, this is a worldship story that flows naturally out of Shepherd’s own speculations. We’ll take a closer look at what Simak has to say in an upcoming post.

Les Shepherd’s original paper on interstellar propulsion is “Interstellar Flight,” JBIS, Vol. 11, 149-167, July 1952, from which the article in Science Fiction Plus was adapted.