In 1966, in the midst of Cold War anxiety, the British economist and political scientist Barbara Ward took up the image of the earth as seen from outer space to describe the delicate political situation of the world: "Modern science and technology have created so close a network of communication, transport, economic interdependence – and potential nuclear destruction – that planet earth, on its journey through infinity, has acquired the intimacy, the fellowship, and the vulnerability of a spaceship." The spaceship reconciled a number of divergent visions of future earth. Next to presenting a 'one-boat' image of humankind, of community and balance of power, the spaceship became a model for sustainable environmental management. At a time of rising environmental consciousness the spaceship combined sufficiency and efficiency ideals of environmental sustainability. While advocates of sufficiency stressed the need for stability through careful resource use and complete material recycling, promoters of efficiency built on development and growth through proficient technological design. Both visions borrowed from the Space Age imagery and the ecologically sufficient and technologically efficient space capsule. Against this background the paper explores the intersections of space technology and ecological research in the decades between 1960 and 1990 with a focus on the design of closed metabolic systems. The paper compares two projects in which the earthly biosphere was experimentalized in the form of self-contained and self-maintained "life-support systems" that could be operated on earth and beyond. Both projects inserted humans into these short-circuited supply systems, for "long-range survival", as system ecologist Howard Odum claimed in 1971. BIOS 3 (USSR, 1960s-1970s) conceptualized human life as biotic mass. In a closed habitat human elements and chlorella algae entered a symbiotic relationship to maintain a viable atmosphere. Biosphere 2 (USA, 1980s-1990s) technologically recreated the major biospheric cycles of the earth on a miniature scale, complete with cycles of soil, air, mineral, water and waste. The figure of the spaceship, so the paper argues, united divergent visions for environmental sustainability through merging subsistence and innovation-based economies. Both projects reconsidered humans' place in nature in different yet related ways, as part of the earth’s life cycles and as top of and in control of its food chains.