In 1997, they put 2 men and 2 women in a 30-foot chamber for 91 days (Schreckenghost et al. 1998b). A physical-chemical air revitalization system recycled the air for 3 of the 4 people, and a wheat crop in the 10-foot chamber did the same for the fourth. The ALS team also experimented with a solid-waste incinerator. Our second ALS AI control system managed the transfer of O2 and CO2 among the gas reservoirs for this test to ensure crew and crop health and to recycle gases produced by waste incineration. These reservoirs included a crew habitat, a plant chamber, an airlock, and a number of pressurized tanks (figure 1). Operating 24 hours a day, 7 days a week, the AI system also used a generative planner that scheduled waste incinerations and crop planting and harvesting, coordinating these tasks with the day-to-day product gas transfer. For both these projects, we used a three-layer architecture (Gat 1998) to design, organize, and develop the control software. AR&SD had used a particular implementation of this architecture known as 3T (see The 3T Intelligent Control System) in a number of robot projects prior to 1995 (Bonasso et al. 1997), and because life support systems are a form of immobots (Williams and Nayak 1996), its application to ALS projects was straightforward.

[FIGURES 4 & 6 OMITTED]Next, the sequencer procedures for the subsystem (RAPS) were installed on the Al workstation and tested with the validated skills. An example of the resulting RAPs is shown in figure 7. There are several methods associated with the processing-start RAP, each indexed by a context clause. The method shown is valid when the required reverse-osmosis stage is purged, and the pps-select valve is open to the postprocessing systems (PPSs). In this case, the RAP starts the reverse-osmosis main feed pump, stops the recirculation pump, and turns the pps-select valve to reject (relieving downstream pressure). Then, the RAP turns the reverse-osmosis process valve to the purge position and turns the pps-select valve to the tank position.

In Colorado, HFH of Metro Denver also builds homes that incorporate passive-solar heating. Large, south-facing windows allow the low-angled winter sun to warm the interiors. Energy-efficient windows and well-insulated walls, floors and foundations retain the solar warmth, reducing demand for auxiliary heating. Because the houses are well-insulated and solar-heated, the furnaces can be downsized substantially. Energy-efficient models are standard. Programmable thermostats regulate backup heating and cooling systems, reducing demand when the house is unoccupied or residents are asleep. Insulation that keeps the houses warm in the winter also helps to maintain a cool interior in Denver''s dry, hot summers. Plus, 2-foot-wide overhangs block the high-angled summer sun and provide shade for walls and windows.

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