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Waste Collection System

The waste collection system is an integrated, multifunctional system used primarily to collect and process biological wastes from crew members in a zero-gravity environment. The WCS is located in the middeck of the orbiter crew compartment in a 29-inch -wide area immediately aft of the crew ingress and egress side hatch. The commode is 27 by 27 by 29 inches and is used like a standard toilet.

The system collects, stores and dries fecal wastes and associated tissues; processes urine and transfers it to the waste water tank; processes EMU condensate water from the airlock and transfers it to the waste water tank if an extravehicular activity is required on a mission; provides an interface for venting trash container gases overboard; provides an interface for dumping ARS waste water overboard in a contingency situation; and transfers ARS waste water to the waste water tank.

A door on the waste management compartment and two privacy curtains attached to the inside of the compartment door provide privacy for crew members. One curtain is attached to the top of the door and interfaces with the edge of the interdeck access, and the other is attached to the door and interfaces with the galley, if installed. The door also serves as an ingress platform during prelaunch (vertical) operations since the flight crew must enter the flight deck over the waste management compartment. The door has a friction hinge and must be open to gain access to the waste management compartment.

The WCS consists of a commode, urinal, fan separators, odor and bacteria filter, vacuum vent quick disconnect and waste collection system controls. The commode contains a single multilayer hydrophobic porous bag liner for collecting and storing solid waste. When the commode is in use, it is pressurized, and transport air flow is provided by the fan separator. When the commode is not in use, it is depressurized for solid waste drying and deactivation. The urinal is essentially a funnel attached to a hose and provides the capability to collect and transport liquid waste to the waste water tank. The fan separator provides transport air flow for the liquid. The fan separators separate the waste liquid from the air flow. The liquid is drawn off to the waste water tank, and the air returns to the crew cabin through the odor and bacteria filter. The filter removes odors and bacteria from the air that returns to the cabin. The vacuum quick disconnect is used to vent liquid directly overboard from equipment connected to the quick disconnect through the vacuum line.

The urinal can accommodate both males and females. The urinal assembly is a flexible hose with attachable funnels for males or females. It can be used in a standing position or can be attached to the commode by a pivoting mounting bracket for use in a sitting position.

All waste collection system gases are ducted from the fan separator into the odor and bacteria filter and then mixed with cabin air. The filter can be removed for in-flight replacement.

The system employs various restraints and adjustments to enable the user to achieve the proper body positioning to urinate or defecate in a zero-gravity environment. Two foot restraints are provided. A toe bar is located at the commode base and is used to urinate standing. It consists of two flexible cylindrical pads on a shaft that can be adjusted to various heights by releasing two locking levers that are turned 90 degrees counterclockwise. The crew member is restrained by slipping the feet under the toe bar restraint. A footrest restrains the feet of a crew member sitting on the commode. It consists of an adjustable platform with detachable Velcro straps for securing the feet. The Velcro straps are wrapped crosswise over each foot and secured around the back. The footrest can be adjusted to various angles and heights. Two locking handles pulled outward adjust the angle; two other locking levers adjust the height of the footrest.

Two body restraints are provided for use when crew members are seated on the commode. The primary restraint is a thigh bar that the crew member lifts up out of the detent position, rotates over the thigh and releases. It exerts a preloaded force on each thigh of approximately 10 pounds. The second restraint is a backup method. It consists of four Velcro fabric thigh straps with a spring hook on one end. Two of the straps are attached to the top front commode surface mating attach points, and the other two are installed on a bracket with five holes on the upper sides of the commode, below and outboard of the thigh bars. The crew member is secured in position by wrapping two straps over each thigh and attaching the mating Velcro surfaces.

Handholds are used for positioning or stabilizing the crew member while using the WCS and form an integral part of the top cover of the waste management collection system assembly.

The controls on the waste collection system are the vacuum valve, fan separator select switch, mode switch, fan separator bypass switches and commode control handle. The system uses dc power to control the fan separators and ac power for fan separator operations. The mode switch and the commode control handle are mechanically interlocked to prevent undesirable system configurations. The remaining controls operate independently. The fan separator bypass switches allow the crew member to manually override a fan separator limit switch failure.

For launch and entry the vacuum valve is closed. During on-orbit operations when the WCS is not in use, the vacuum valve is opened. This exposes the commode (overboard) via the vacuum vent system, and any solid wastes in the commode are dried. The hydrophobic bag liner in the commode allows gas from the commode to vent overboard, but does not allow the passage of free liquid.

In the urine collection mode, the vacuum valve remains in open. The fan sep select switch is positioned to 1 or 2 . When positioned to 1, main bus A dc power is supplied to the mode switch; and when positioned to 2 , MNB dc power is supplied to the mode switch. The mode switch positioned to WCS/EMU energizes a relay for a fan separator (dependent on fan sep 1 or 2 position). The active fan separator pulls cabin air flow through the urinal at 8 cubic feet per minute and ballast cabin air through the wet-trash storage modules at 30 cubic feet per minute. The ballast air mixes with the urine transport air flow in the fan separator. The fan separator is designed to operate at 38 cubic feet per minute and thus requires the 30-cubic- feet-per-minute ballast air flow. Liquid check valves at the waste water outlet from each fan separator provide a back pressure for proper separator operation and prevent backflow through the non-operating separator.

The liquid and air mixture from the urinal line enters the fan separator axially and is carried to a rotating chamber. The mixture first contacts a rotating impact separator that throws the liquid to the outer walls of the rotating fluid reservoir. Centrifugal force separates the liquid and draws it into a stationary pitot tube in a reservoir and directs the liquid to the waste water tank. Air is drawn out of the rotating chamber by a blower that passes the air through the odor and bacteria filter, where it mixes with cabin air and re-enters the crew cabin.

In the EMU and airlock water collection mode, a guard is rotated over the mode switch to preclude WCS use or deactivation during the EMU and airlock water collection mode. A urinal protective screen cap is installed on the urinal because it cannot be used during the EMU dump because of possible separator flooding. The EMU dump will be used only if an EVA is required on a mission. The EMU waste water is dumped through waste water valves in the airlock. Other than these requirements, EMU dump is the same as the urine collection mode.

In the urine and feces collection mode, the commode control handle is pulled up, and the commode is pressurized with cabin air through the debris screen and flow restrictor in approximately 20 sec onds. (Note that if the mode switch is positioned to off , the handle cannot be pulled up because of a mechanical interlock.) The commode control handle is positioned to push fwd after 20 sec onds (it cannot be pushed forward until after 20 seconds because of the delta pressure across the sliding gate valve, and it cannot be pushed forward unless the mode switch is positioned all the way to the WCS/EMU position). When the commode control handle is pushed forward, the sliding gate valve on the commode is opened. The commode outlet control valve and ballast air control valves are positioned to connect the commode to the fan separator, and the commode pressurization valve is closed. The WCS is used like a normal toilet. The commode seat is made of a contoured, compliant, semisoft material that provides proper positioning of the user and is sealed to minimize air leakage. Feces enter the commode through the 4-inch-diameter seat opening and are drawn in by cabin air flowing through holes under the seat at 30 cubic feet per minute. Fecal matter and tissues are deposited on the porous bag liner, and the air is drawn through the hydrophobic material to the fan separator. The hydrophobic liner material prevents free liquid and bacteria from leaving the collector. (Toilet tissue is the only paper item permitted to be disposed of in the commode.) Urine is processed as in the urine collection mode. The off/down position closes the sliding gate valve and depressurizes the commode for deactivation and solid waste drying. If the handle is left partially up, it would cause loss of cabin air through the vacuum vent. After usage, the WCS should be cleaned with wet wipes, if required, to maintain an odorless and sanitary environment. The seat can be lifted for cleaning, and the WCS should be cleaned once a day with a biocidal cleanser. The urinal should also be cleaned and flushed with water once a day.

The vacuum vent quick disconnect provides the capability to dump ARS waste water overboard through the vacuum vent by connecting a water transfer hose to the vacuum vent quick disconnect and the waste water crosstie quick disconnect.

If fan separator 1 is inoperative or fails to achieve proper operational speed (which can be verified by a reduced noise level or lack of air flow), the fan sep switch is positioned from 1 to 2, and fan separator 2 will operate in the same manner as 1.

The fan sep 1 bypass and fan sep 2 bypass switches permit the crew members to manually override a fan separator limit switch failure either in the fan sep or mode switches. The bypass switches are located on the waste collector and are lever-locked. When either switch is positioned to on, dc power is applied to the corresponding relay, energizing it and providing ac power to activate the corresponding fan separator. Both separator bypass switches should not be on at the same time. Before the fan sep bypass switch is activated, the fan sep select switch should be positioned in the corresponding fan separator position to preset the fan separator inlet valve, and the mode switch should be positioned to WCS/EMU to preset the urine collection valve.

A vacuum vent isolation valve is located in the vacuum vent line from the waste collector to the overboard vacuum line. It is controlled by the vacuum vent control switch on panel ML31C. This switch receives electrical power from the vacuum vent bus select switch on panel ML31C when the bus select switch is positioned to MNA or MNB . When the control switch is positioned to open , the vacuum vent isolation valve is opened, allowing the vacuum vent line to be open to vacuum. A talkback indicator next to the control switch indicates op when the valve is open, barberpole when the valve is in transit and cl when the valve is closed. The off position of the control switch closes the valve.

Thermostatically controlled heaters are installed on the vacuum vent line. Electrical power for the A and B heaters are from the respective H2O line htr A and B circuit breakers on panel ML86B. (These circuit breakers also supply electrical power to supply water dump line A and B heaters and waste water line A and B heaters.)

Heaters are also installed on the vacuum vent nozzle and are controlled by the vacuum vent noz htr switch on panel ML31C. Electrical power is supplied to the vacuum vent nozzle heaters when the switch is positioned to on. The off position removes electrical power from the vacuum vent nozzle heaters.

If both fan separators in the waste collection system fail, feces are collected by the Apollo fecal bag. To dispose of the Apollo fecal bag, the waste collection system is configured as in the urine and feces collection mode and the bag is stowed in the commode.

If both fan separators in the waste collection system fail and it is not possible to dump urine overboard, urine may be collected using a contingency urine collection device.


Curator: Kim Dismukes | Responsible NASA Official: John Ira Petty | Updated: 04/07/2002
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