Generation ship

A generation ship, generation starship, or world ship is a hypothetical type of interstellar ark, a multi-generational space habitat and starship. It is a design to allow travel times of hundreds to thousands of years to reach nearby stars. The original occupants of a generation ship would grow old and die, leaving their descendants to continue traveling.

History

Origins Rocket pioneer Robert H. Goddard was the first to write about long-duration interstellar journeys in his "The Ultimate Migration" (1918). In this, he described the death of the Sun and the necessity of an "interstellar ark". The crew would travel for centuries in suspended animation and be awakened when they reached another star system. He proposed to use small moons or asteroids as ships, and speculated that the crew would endure psychological and genetic changes over the generations. Konstantin Tsiolkovsky, considered a father of astronautic theory, first described the need for multiple generations of passengers in his essay, "The Future of Earth and Mankind" (1928), outlining a space colony equipped with engines that travels thousands of years which he called "Noah's Ark". In the story, the crew had changed so much over the generations at so many levels that they did not even acknowledge Earth as their home planet. Another early description of a generation ship is in the 1929 essay "The World, the Flesh, & the Devil" by John Desmond Bernal. Bernal's essay was the first publication to reach the public and influence other writers. He wrote about the concept of human evolution and mankind's future in space through methods of living that we now describe as a generation starship, and which could be seen in the generic word "globes".

World Ships – Architectures & Feasibility Revisited paper

The 2012 paper World Ships – Architectures & Feasibility Revisited differentiated several types of interstellar spacecraft: those with a population bigger than 100,000 are called world ships, while those with a population between 1,000 and 100,000 are called colony ships. Interstellar spacecraft with a population below 1,000 are called sprinter if their cruise velocity is bigger than 10% of c, and slow boat if smaller. The paper also described a proposed world ship, having the minimal population to be considered as such (100,000), and consisting of 4 stacked Stanford torus colonies (with some changes from the original, such as having 2.5 times its population, and a 10% bigger mass), and a propulsion and power generation system based on Project Daedalus. The Stanford torus was chosen because of its detailed design, that covers in-depth aspects such as life support systems and wall thickness. The study also concluded that a world ship would need an automatic fail detection and self-repair system, to be reliable enough for its mission, preventing failures from having catastrophic effects.

Project Hyperion Project Hyperion, launched in December 2011 by Andreas M. Hein, intends to perform a preliminary study that defines integrated concepts for a crewed interstellar generation ship. It has led to the most detailed designs of generation ships to date. The project is associated with the Initiative for Interstellar Studies and has its origins with the WARR student group at the Technical University of Munich. The study aims to assess the feasibility of crewed interstellar flight using current and near-future technologies. It also aims to guide future research and technology development plans as well as to inform the public about crewed interstellar travel. Notable results of the project include an assessment of world ship system architectures and adequate population size. A survey paper on generation ships has been presented at the ESA Interstellar Workshop in 2019 as well as in ESA's Acta Futura journal. An interdisciplinary design competition was launched in 2024. Results were announced in July 2025 with the Italian Chrysalis team on the 1st place, the Polish WFP Extreme 2nd, and the Malaysian Systema Stellare Proximum on 3rd place.

Definition According to Hein et al., a "generation ship" is a spacecraft on which a crew is living on board for at least several decades, such that it comprises multiple generations. Several sub-categories of generation ships are distinguished: sprinter, slow boat, colony ship, world ship. The Enzmann starship is categorized as a "slow boat" because of the Astronomy Magazine title "Slow Boat to Centauri" (1977). Gregory Matloff's concept is called a "colony ship" and Alan Bond called his concept a "world ship". These definitions are essentially based on the velocity of the ship and population size.

Obstacles

Destination The first generation ships need to balance high cost with the uncertain probability that a destination star system is sufficiently hospitable.

Biosphere Such a ship would have to be entirely self-sustaining, providing life support for everyone aboard. It must have extraordinarily reliable systems that could be maintained by the ship's inhabitants over long periods of time. This would require testing whether thousands of humans could survive on their own before sending them beyond the reach of help. Small artificial closed ecosystems, such as Biosphere 2, have been built in an attempt to examine the engineering challenges of such a system, with mixed results.

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