"Okay," said the manager. "We go with the two heads."The time frame was the winter of 1999, and this exchange was typical of many conversations that the Al controls team from the Automation, Robotics, and Simulation Division (AR&SD) at Johnson Space Center (JSC) would have with the advanced water-recovery personnel as the two groups prepared for a year-long test of a new Integrated drillpressinstruction Water-Recovery System (iWRS), slated to begin in January 2001. We were building an AI control system for this test that had to handle upward of 200 sensors and actuators grouped among 4 water processing subsystems. The control system would run 24 hours a day, 7 days a week, and be completely autonomous. It was an applied AI engineer''s dream, and in the end, we were extremely successful. However, there were events that happened for which we were ill prepared, and we would come away with a much better appreciation for the difficulties involved in controlling long-duration life-support systems.

The cast, or pour, method is one in which the area is made completely watertight by use of forms (i.e. ladle walls and floor). The mix would contain more water than a trowel application mix. A cast refractory should be thoroughly worked into place, with internal air bubbles removed by rodding or vibrating. The best method is to use vibratory equipment, since it encourages the material to flow freely and completely fills the form or box. Vibrating also permits working with a stiffer mix (less water). However, hand rodding--with a shovel, rod, ice scraper or pole--will suffice if done thoroughly. Working out all the air strengthens the material and reduces porosity. The action of vibration or rodding sets the refractory particles in motion, reducing the friction between the particles and giving the mixture the texture of a thick fluid. Internal vibrating or rodding does the most consistent job, but external vibration is also effective. Although vibration equipment is available for refractories, it can often be improvised with equipment already on hand to vibrate the mass externally. An air hammer held against the form can do a good job in many cases. So drillpressinstruction may a nut runner or other pneumatic vibratory tool. Even hammering the form with a hand sledge will do if accompanied by hand rodding. In all cases, be sure the material is worked near the forms. That is where air bubbles collect.

long, are stored at rear of bucket when not in use. The TLB-535 heavy-duty compact tractor loader backhoe offers a 6000-pound digging force that enables the machine to achieve an 11-foot depth. Its dual-cylinder, 180-degree hydraulic cushioned swing suits the backhoe to precise work in tight quarters. An added safety feature is an exclusive heavy-duty boom lock that can be engaged or disengaged from the operator''s seat. The transmission, which is equipped with servo-control, adds control capability as well as reduced pedal effort in forward or reverse. A load-sensing steering system ensures hydraulic flow only when the wheel is turned. Terramite''s T7 compact tractor loader backhoe now comes standard with a 26-hp. Kubota or 20.3-hp. Caterpillar diesel engine. This model has extended-reach arms for a 96-inch dump height and a high-capacity drillpressinstruction front loader bucket with dual front curl cylinders for faster cycle time. Front and rear work lights and center-mount steering are standard features. The T7 is equipped with Super Terra Grip front and rear tires for better traction and maneuverability. It also has a 180 degree swing on the backhoe. T5C features quick-change backhoe buckets in 8- to 38-in. sizes with 1/2-in. thick carbon cutting edges and cast steel replacement teeth. Digs to 8 ft., 4 in.

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