World ships: Feasibility and Rationale

Abstract: World ships are hypothetical, large, self-contained spacecraft for crewed interstellar travel, taking centuries to reach other stars. Due to their crewed nature, size, and long trip times, the feasibility of world ships faces an additional set of challenges compared to interstellar probes. Despite their emergence in the 1980s, most of these topics remain unexplored. This article revisits some of the key feasibility issues of world ships. First, definitions of world ships from the literature are revisited and the notion of world ship positioned with respect to similar concepts such as generation ships. Second, the key question of population size is revisited in light of recent results from the literature. Third, socio-technical and economic feasibility issues are evaluated. Finally, world ships are compared to potential alternative modes of crewed interstellar travel. Key roadblocks for world ships are the considerable resources required, shifting its economic feasibility beyond the year 2300, and the development of a maintenance system capable of detecting, replacing, and repairing several components per second. The emergence of alternative, less costly modes of crewed interstellar travel at an earlier point in time might render world ships obsolete.

• The paper’s main finding is that world ships face significant biological, technical, and economic hurdles for sustainable interstellar journeys.
• It employs agent-based models and historical perspectives to refine minimum viable populations and habitat maintenance strategies.
• The research also considers alternatives like sleeper and seed ships, which may offer more practical approaches to crewed interstellar travel.

An In-Depth Analysis of World Ships: Feasibility and Implications

The concept of world ships, large self-contained spacecraft designed for centuries-long interstellar journeys, has been a subject of fascination since the 1980s. These ships offer a unique proposition for crewed interstellar travel, yet face significant feasibility challenges, distinct from those encountered by interstellar probes due to the requirements of size, self-sufficiency, and long-duration habitats. This paper revisits the concept and evaluates the multifaceted feasibility of world ships, encompassing biological, technical, economic, and alternative considerations.

Definitional Context and Historical Perspectives

World ships are distinguished by their substantial population sizes, covering over 100,000 individuals, traveling at velocities below 1% of the speed of light. The paper revisits definitions from key literature, extending them to include new potential designs, such as planet-sized habitats analogous to a McKendree Cylinder.

The notion of world ships first gained extensive attention in the 1984 issue of the Journal of the British Interplanetary Society. These discussions highlighted fundamental engineering challenges, including habitation environments and societal stability over millennia.

Feasibility Challenges: An Analytical Framework

The examination of world ships is decomposed into several feasibility domains.

Biological and Cultural Feasibility

The paper explores the minimum viable population necessary for genetic health and socio-cultural continuity. Earlier estimates ranged broadly from 80 individuals to multiple thousands. Recent advancements using agent-based models have refined these numbers, with Marin et al. indicating that as few as 98 may suffice, albeit with significant social engineering. Nevertheless, the practicality of sustaining a genetically and socially healthy population necessitates further empirical research.

Socio-Technical Considerations

World ships must fulfill reliability standards capable of autonomous maintenance over centuries. The replacement and repair system must function continuously, suggesting the potential need for an advanced AI-driven maintenance protocol. Furthermore, the balance between population size and trip duration emphasizes the necessity for spacecraft velocities exceeding 1% of the speed of light to remain viable.

Economic and Alternative Modes

The feasibility from an economic lens emphasizes the resource-intensive nature of world ships, placing their realistic construction and launch beyond 2300 under stable economic growth models. Alternatives such as sleeper ships, carrying humans in cryogenic states, seed ships utilizing embryos, and digital emulation ships, present potentially less costly crewed interstellar travel methods. These alternatives might surpass world ships in practical desirability due to reduced resource dependencies.

Implications and Future Trajectories

The paper concludes by evaluating the implications of existing world ship models against broader interstellar travel paradigms. While their feasibility might wane in light of emerging technologies, they represent a compelling vision for mobile habitats within Solar System bounds. The research underscores the necessity of considering socio-cultural and technical reliability factors, which are not solely technical challenges but essential to any long-term space habitation endeavor.

Overall, this paper offers a rigorous exploration of the current and future potential of world ships, advocating for continued research into their biological, societal, and technical aspects. As humanity approaches an era of increased space exploration capability, understanding these concepts will be critical for engaging with the possibilities of interstellar colonization.