The biosphere 2 project and its potential role in assisting space exploration
Abstract Space Biospheres Ventures is developing technologies for its Biosphere 2 project — a 3 acre materially closed ecological system with human habitat, intensive agriculture and five wilderness biomes — and other life-support testbeds for space habitats in microgravity and the Moon and Mars, as well as for ecological research pertinent to the biosphere of Earth. These include soil bed reactors for air purification and biomass production; aquatic waste processing systems; real-time analytic systems; and computer systems of control and management. A space policy pursuing joint Earth and ‘space biospheres’ objectives and implications is discussed.
Sustainable food production for a complete diet
Home gardens provide relatively little supplemental food or in come for most practitioners in the United States (Utzinger and Connolly, 1978; Wishnetsky and Cash, 1976). but they can be important sources of supplemental nutrition and income for people in developing countries (Gershon and Yen-Ching. 1984; Mullane, 1981; O’Brien-Place, 1987; Yoon, 1983). Family gardens can provide a form of food security if they are keyed to specific nutritional needs (Gershon and Yen-Ching. 1984; Popkin et al.. 1980). The extent to which it is practical to produce a complete diet in a garden is unknown. Duhon and Gebhard (1985) are representative of an organic fanning movement that advocates complete food independence through sustainable family gardens. They estimate that a complete diet can be produced on as little as 100 m of land with few external inputs. NASA estimates of the space to produce a complete diet are as low as 25 m (Hoff et al., 1982). To our knowledge, these estimates have not been verified experimentally. We have helped to develop the food production system for Biosphere II. a closed, I-ha ecosystem in which eight people will grow their own food using natural desert soil and sustainable meth ods. As a pretest of the system, we have attempted to produce all of the elements of a complete diet. made up of a diverse collection of food crops, on a minimal area in Tucson, Ariz. The experiment tested the feasibility of producing all or most of a family’s nutritional needs on a small piece of soil using manual labor and no outside inputs. The experiment was conducted in a greenhouse to simulate the continuous cropping conditions that exist in tropical locations (Sanchez and Benites. 1987) as well as the conditions expected in Biosphere II and possible future space habitations (Hoff et al., 1982).
Velocity moments in alongshore bottom stress parameterizations
The time-averaged alongshore bottom stress is an important component of nearshore circulation models. In a widely accepted formulation the bottom stress is proportional to , the time average of the product of the instantaneous velocity magnitude |u→| and the instantaneous alongshore velocity component υ. Both mean and fluctuating (owing to random, directionally spread waves) velocities contribute to . Direct estimation of requires a more detailed specification of the velocity field than is usually available, so the term is parameterized. Here direct estimates of based on time series of near-bottom currents observed between the shoreline and 8-m water depth are used to test the accuracy of parameterizations. Common parameterizations that are linear in the mean alongshore current significantly underestimate for moderately strong alongshore currents, resulting in overestimation of a drag coefficient determined by fitting modeled (with a linearized bottom stress) to observed alongshore currents. A parameterization based on a joint-Gaussian velocity field with the observed velocity statistics gives excellent overall agreement with the directly estimated and allows analytic investigation of the statistical properties of the velocity field that govern . Except for the weakest flows, depends strongly on the mean alongshore current and the total velocity variance but depends only weakly on the mean wave angle, wave directional spread, and mean cross-shore current. Several other nonlinear parameterizations of are shown to be more accurate than the linear parameterizations and are adequate for many modeling purposes.