Talking about Mason Peck’s notions of ‘swarm’ spacecraft — probes on a chip that might reach interstellar speeds — I’m inescapably drawn to the other end of the spectrum. A ‘worldship’ is a mighty creation that may mass in the millions of tons, a kilometer (or more) long vehicle that moves at a small fraction of the speed of light but can accommodate thousands, if not hundreds of thousands, of inhabitants. What promises to be the first scientific conference devoted solely to worldships is about to take place on Lambeth Road in London at the headquarters of the British Interplanetary Society. The day-long conference gets down to business on the morning of August 17. This BIS page offers a draft of the program.
As the BIS has done in the past, all presentations from the conference will be written up in a special issue of the Journal of the British Interplanetary Society, where much of the early speculation on worldships has taken place. Several of the Project Icarus team will be presenting papers and I notice that solar sail expert Gregory Matloff, one of the analysts of worldship ideas in the pages of JBIS back in the 1980s, will be represented with a paper on sail options for such a mission. Beyond that, the conference aims, in the words of its organizers, “to reinvigorate thinking on this topic and to promote new ideas.” It will “focus on the concepts, cause, cost, construction and engineering feasibility as well as sociological issues associated with the human crew.”
Image: A worldship may eventually take shape by drawing on the design of space habitats built closer to home. Credit: Don Davis.
Those of you who are familiar with The Starflight Handbook, Matloff’s seminal work on interstellar concepts (John Wiley & Sons, 1989) may recall a write-up on a mission called Sark-1, described as a ‘solar sail interstellar ark’ and named in honor not only of the sailing vessel Cutty Sark but the whiskey that now bears its image. The latter reference is a nod to the fact that a generous store of spirits would not go amiss for those involved in a journey scheduled to last at least a thousand years.
The Sark-1 would be, in comparison to some of the behemoth worldship concepts that have followed, a relatively small vessel, carrying a ‘modest’ crew of 1000 to the Alpha Centauri system. Working with Eugene Mallove, Matloff went on to allot roughly 40 square yards of living space for each person, lodged within a toroidal cabin structure that would weigh 2500 metric tons on the Earth’s surface. Now figure 1000 tons of atmosphere, supplies and power plant adding up to 2000 tons, giving you a basic 5500-ton space colony minus the essential sail. The authors then round the number up to 10,000 tons, thus providing for supplies needed upon arrival.
You make a lot of assumptions when trying to design something that only futuristic technology can deliver. Matloff and Mallove divide the colony into a fleet of six starships, each towed by a circular sail 380 kilometers in diameter, and assume micro-fine filaments of diamond for support cables. For propulsion, a close solar pass would involve an initial perihelion velocity of 0.0014 c, making travel time to Alpha Centauri about 1350 years. The sail — folded and stowed during the cruise phase — would be redeployed upon approach to the Centauri stars, electrically charged and used for deceleration. What the authors say next meshes nicely with the upcoming conference:
Missions by solar sail starship habitats lasting millennia may never be attractive to terrestrials. However, long-term residents of space colonies in the solar system or members of other spacefaring civilizations in the galaxy may not feel equally constrained. Furthermore, as we have seen, there may be undiscovered stars much closer than Alpha Centauri, so we may eventually discover destinations only a few centuries away via inhabited solar sail starships. So in addition to research on solar sail materials, starship dynamics, and logistics, it is not too soon to undertake sociological studies of the problems of maintaining interstellar colonies. Whether clipper ships of the galaxy will ply the interstellar ocean in the twenty-first century, as white-sailed Yankee clippers once did in the nineteenth, is a question our children may be able to answer.
Moving well beyond Sark-1, a true worldship would need to approximate a terrestrial environment inside a far larger vessel. The idea, after all, is to deliver a population of colonists who are not only equipped for the job but sane enough to accomplish it. That may well require structures on the scale of an O’Neill habitat, gigantic vessels housing many of the amenities we take for granted on a planetary surface — parks, lakes, farms — with ample room for living and carrying out a rewarding life as the interminable journey progresses. The typical Earth-dweller isn’t designed for such a mission, but long-term colony structures in the Solar System may one day breed a population for which living on a planetary surface is something of an anomaly. Will the descendants of this kind of habitat head out to become our first interstellar colonists?
For more, see Matloff and Ubell, “Worldships: Prospects for Non-nuclear Propulsion and Power Sources,” JBIS 38 (June 1985), pp. 253-261. See also Matloff and Mallove, “The First Interstellar Colonization Mission,” JBIS 33 (March, 1980), pp. 84-88.