Supply and Waste Water

The supply and waste water systems provide water for the flash evaporator, crew consumption and hygiene. The supply water system stores water generated by the fuel cell power plants, and the waste water system stores waste from the crew cabin humidity separator and from the flight crew. There are four supply water tanks and one waste water tank located beneath the crew compartment middeck floor.

Each of the four potable water tanks has a usable capacity of 165 pounds, is 35.5 inches in length and 15.5 inches in diameter, and weighs 39.5 pounds dry.

The waste water tank's usable capacity is 165 pounds. It is 35.5 inches in length and 15.5 inches in diameter and weighs 39.5 pounds dry.

The three fuel cell power plants generate a maximum of 25 pounds of potable water per hour. The product water from all three fuel cell power plants flows to a single water relief control panel. The water can be directed to potable water tank A or to the fuel cell power plant water relief nozzle. Normally, the water is directed to water tank A. If a line ruptured in the vicinity of the single water relief panel, water could spray on all three water relief panel lines, causing them to freeze and preventing the fuel cell power plants from discharging water, which would cause flooding of the fuel cell power plants. The product water lines from all three fuel cell power plants were modified to incorporate a parallel (redundant) path of product water to potable water tank B in the event of a freeze-up of the single water relief panel. In the event of a water freeze-up, pressure would build up and relieve through the redundant paths to potable water tank B. Temperature sensors are installed on each of the redundant paths in addition to a pressure sensor that is transmitted to telemetry.

A water purity sensor (pH) was added at the common product water outlet of the water relief panel. It provides a redundant measurement of water purity-a single measurement of water purity in each fuel cell power plant was provided previously. If the single fuel cell power plant pH sensor failed, the flight crew was required to sample the potable water.

The hydrogen-enriched water from the fuel cell power plants that flows through the single water relief panel to potable tank A passes through two hydrogen separators, where 85 percent of the excess hydrogen is removed. The hydrogen separators consist of a matrix of silver palladium tubes, which have an affinity for hydrogen. The hydrogen is dumped overboard through a vacuum vent.

Water passing through the hydrogen separators can be stored in all four potable water tanks. The four potable water tanks are identified as tanks A, B, C and D. The water entering tank A passes through a microbial filter that adds approximately one-half parts per million iodine to the water. The water stored in tank A is normally used for flight crew consumption but could also be used for flash evaporator cooling. The water from the microbial check valve is also directed to a galley supply valve. If the water tank A inlet valve is closed or tank A is full, water is directed to tank B through a 1.5-psid check valve where it branches off to tank B. If the tank B inlet valve is closed or tank B is full of water, the water is directed through another 1.5-psid check valve to the inlets to tanks C and D.

Each potable water tank has an inlet and outlet valve that can be opened or closed selectively to use water; however, the tank A outlet valve normally remains closed since the water has been treated by passage through the microbial filter for flight crew consumption.

The controls and displays for the potable water tank supply system are located on panels R12 and ML31C. Potable water tanks A, B and C are controlled from panel R12, and tank D is controlled from panel ML31C.

When the supply H 2 O inlet tk A , B or C switch on panel R12 is positioned to open , the inlet valve for the tank permits water into that tank. A talkback indicator next to the corresponding switch on panel R12 indicates op when the corresponding valve is open, barberpole when the valve is in transit and cl when that valve is closed. When the switch is positioned to close, the water inlet to that tank is isolated from the inlet water supply. The supply H 2 O tk inlet D switch and talkback indicator are located on panel ML31C and operate in the same manner as the switches and talkbacks for tanks A, B and C.

Each potable water and waste water tank is pressurized with gaseous nitrogen from the crew compartment nitrogen supply system. Nitrogen supply systems 1 and 2 can be used individually to pressurize the tanks with nitrogen at 16 psig. Nitrogen supply system 1 is controlled by the water tank nitrogen regulator inlet and water tank nitrogen isolation 1 manual valves from panel M010W. Nitrogen supply system 2 is controlled by the water tank nitrogen regulator inlet and water tank nitrogen isolation 2 manual valves from panel M010W. The regulator in each nitrogen supply system controls the nitrogen pressure to the tanks at 16 psig, and a relief valve in each nitrogen supply system will relieve into the crew cabin if the nitrogen supply increases to 18.5 psig, plus or minus 1.5 psig, to protect the tanks from overpressurization.

For only tank A, inlet nitrogen pressure is controlled by pressure and vent manual valves on panel ML26C. When the tank A isolation valve is closed, the tank A vent valve is opened to the crew cabin atmosphere. For launch the tank A isolation valve is closed, which lowers tank A pressure so the fuel cell power plants' water head pressure is lower to help prevent flooding of the fuel cell power plants during ascent. On orbit the tank A isolation valve is opened, and the tank A vent to the cabin is closed, allowing nitrogen supply pressure to tank A and inhibiting cabin atmosphere to tank A. Nitrogen supply pressure is supplied to tanks B, C and D to support flash evaporator operation.

If neither nitrogen supply system 1 nor 2 can be used to pressurize the water tanks, the H 2 O alternate press switch on panel L1 can be positioned to open, which would reference the water tank pressurization system to the crew compartment ambient pressure. Normally, this switch is positioned to close to isolate the cabin pressurization system from the water tank pressurization system.

The supply H2O outlet tk A, B or C switch on panel R12 positioned to open permits water from the corresponding tank to flow from the tank into the water outlet manifold by the tank nitrogen pressurization system. A talkback indicator next to the switch would indicate op when that valve is open, barberpole when it is in transit and cl when it is closed. The close position of each switch isolates that water tank from the water outlet manifold. The supply H 2 O tk inlet D switch and talkback indicator are located on panel ML31C and operate in the same manner as the tank A, B and C switches and talkback indicators on panel R12.

If the potable water tank A or B outlet valve is opened, water from the corresponding tank is directed to the water outlet manifold. The tank A and B water is then available to the extravehicular mobility unit fill in the airlock, to the flash evaporator water supply system A and to the water dump. As stated previously, the tank A outlet valve is normally closed to prevent contamination of the water in tank A. Thus, tank B would supply water to flash evaporator water supply system A and to the EMU fill in the airlock. If it is necessary to provide space for storing water in tank A and/or B, tank A and/or B water can be dumped overboard.

Tank C or D is normally saved full of water for contingency purposes. If the tank C or D outlet valve is opened, water from either tank is directed to the water outlet manifold. The water is then available to the flash evaporator water supply system B.

A crossover valve installed in the water outlet manifold is controlled by the supply H2O crossover vlv switch on panel R12. When the switch is positioned to open , the crossover valve opens and allows tank A or B to supply flash evaporator water supply systems A and B, the EMU fill in the airlock and water dump. It would also allow tank C or D to supply flash evaporator water supply systems A and B, the EMU fill in the airlock and water dump. A talkback indicator next to the switch indicates op when the crossover valve is opened, barberpole when the valve is in transit and cl when the valve is closed. The close position isolates the water manifold between the tank A and B outlets and the tank C and D outlets.

Water from supply system A is routed directly to the flash evaporator. Water from system B is routed to an isolation valve in the system. The valve is controlled by the supply H 2 O B supply isol vlv switch on panel R12. When the switch is positioned to open , water from supply system B is directed to the flash evaporator. A talkback indicator next to the switch indicates op when the valve is opened, barberpole when it is in transit and cl when the valve is closed. The close position isolates water supply system B from the flash evaporator.

Potable water from tank A or B can be dumped overboard, if necessary, through a dump isolation valve and a dump valve. Potable water from tank C or D can also be dumped overboard, if necessary, through the crossover valve and through the dump isolation valve and dump valve. The overboard dump isolation valve is located in the crew cabin, and the dump valve is located in the midfuselage. The dump isolation valve is controlled by the supply H2O dump isol vlv switch on panel R12; the dump valve is controlled by supply H2O dump vlv switch on panel R12. The supply H2O dump valve enable/noz htr switch on panel R12 must be positioned to on to supply electrical power to the supply H 2 O dump vlv switch. When each switch is positioned to open , the corresponding valve is opened, which allows potable water to be dumped overboard. A talkback indicator next to each switch indicates op when the corresponding valve is open, barberpole when it is in transit and cl when it is closed. Closing either valve inhibits the dumping of potable water. At the completion of the dump, each switch is positioned to close to close the corresponding valve.

A contingency crosstie valve, in the supply water overboard dump line between the dump isolation valve and dump valve, permits the joining of the waste water system through a flexible hose to the supply water system for emergency dumping of waste water through the supply water dump or the use of waste water for the flash evaporators.

The potable supply water dump nozzle employs a heater to prevent freezing of the supply water dump nozzle at the midfuselage. The dump nozzle heater is powered when the supply H 2 O dump vlv enable/noz htr switch on panel R12 is positioned to on . When the switch is positioned to off, it removes electrical power from the nozzle heater as well as the supply H2O dump vlv switch, which causes the dump valve to close.

The potable supply water line upstream of the water dump nozzle has electrical heaters on the line to prevent supply water from freezing. The A and B heaters on the line are thermostatically controlled and are powered by the H2O line heater A and B circuit breakers on panel M186B. (These circuit breakers also provide power to thermostatically controlled heaters on the waste water line and the waste collection system vacuum vent line.)

The potable supply water feed lines to the flash evaporators are approximately 100 feet long. To prevent the water in the lines from freezing, redundant heaters are installed along the length of the water lines. The heaters are controlled by the flash evap feed-line heater A supply and B supply switches on panel L2. When a switch is positioned to 1, it enables the thermostatically controlled heaters on the corresponding supply line to automatically control the temperature on that line. When a switch is positioned to 2, it enables another thermostatically controlled heater system on the corresponding supply line. The off position of each switch inhibits heater operation on the corresponding supply line.

The galley supply valve in the supply water line from the microbial filter permits or isolates the supply water from the microbial filter to the middeck ECLSS supply water bay. When the switch is positioned to open , supply water is routed through parallel paths; one path flows through the ARS water coolant loop water chiller to cool the supply water, and the other path bypasses the water chiller with ambient water. A talkback indicator next to the switch indicates op when the valve is open, barberpole when the valve is in transit and cl when the valve is closed. The close position of the switch isolates the potable supply water from the middeck ECLSS supply water panel.

If a payload is installed in the middeck in lieu of the galley, the chilled water and ambient water are connected to an Apollo water dispenser to dispense ambient and chilled water for drinking and food reconstitution. The temperature of the chilled water is within the range of 43 to 55 F, and the ambient water's temperature is between 65 to 95 F. A personal hygiene dispenser is also provided with ambient water.

If the galley is installed in the middeck of the crew cabin, the water supply is directed to the galley. A hot-water heater heats water to 155 to 165 F. Chilled water is also provided at 45 to 55 F.