In the August 2020 Issue of Principium, Richard Soilleux summarizes current research on the feasibility of interstellar voyages via multi-generation worldships. The starting point is assumed to be free flying orbital settlements as envisioned by Gerard K. O’Neill that will eventually be tooling around the solar system way before a trip to the stars would be possible. The baseline for the analysis was an orbital space settlement called Avalon, the result of a complex study by the British Interplanetary Society called the BIS Space Project which took a fresh look at O’Neill’s smallest habitat Island 1, a settlement that would house 10,000 inhabitants.
Much of the technology needed for an interplanetary ship like Avalon could be leveraged for an interstellar craft, but there are several challenges for permanent occupation over many generations as would be needed for a trip to the stars. For example, the ships would obviously have to be much more robust and reliable. Design lifetimes of 1000 years, as what is estimated to be needed, would require rigorous maintenance and repair schedules. Major periodic replacement of damaged or worn components and obsolete parts would also be required.
Soilleux’s analysis breaks down the key features of the settlement in terms of technology readiness and extrapolates to the interstellar case. One key element of the design is the environmental control and life support system (ECLSS). Avalon’s ECLSS does not need to be fully closed when voyages are limited to within the solar system as there are plenty of resources to replace nutrients and materials that cannot be recycled. Interstellar voyages are another matter all together and the study found that the recycling rate needs to be better than 90% for at least 36% of a material to remain useable after 100 years. This ratio would have to be significantly higher for an interstellar journey, the duration of which could be an order of magnitude longer. Soilleux concludes that “Recycling must therefore be managed carefully, and a detailed inventory maintained of all materials and nutrients wherever they are in the system.”
ECLSS technology is clearly one of the gating items for space settlement in the solar system and for journeys beyond. More information and research can be found in the Life Support Section.
