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WATER COOLANT LOOP SYSTEM

WATER COOLANT LOOP SYSTEM

The WCLS provides thermal conditioning of the crew cabin by collecting heat at the cabin-air-to-water-coolant-loop heat exchanger and transfers heat to the water coolant loops. The water coolant loops transfer the heat at the water and Freon-21 coolant loop interchanger. The WCLS also provides thermal conditioning for the three avionics bays by an air-to-water heat exchanger in each avionics bay, the cabin heat exchanger, liquid-cooled garament and water chiller, which transfers heat to the water coolant loops. The IMU air-to-water heat exchanger also transfers heat to the water coolant loops.

There are two complete and separate water coolant loops that flow side by side and can operate at the same time. The only difference between water coolant loops 1 and 2 is that loop 1 has two water pumps and loop 2 has one pump.

Some electronic units in each of the avionics equipment bays are mounted on cold plates. The water coolant loops flow through the cold plates, and the heat generated by the electronics unit is transferred to the cold plate and then to the water coolant loop, which carries heat from the electronic unit. The cold plates mounted on the shelves in each avionics equipment bay are connected in a series-parallel arrangement with respect to the water coolant loop flow.

The water pumps in coolant loop 1 are controlled by the H2O pump loop 1 A and B switch on panel L1 in conjunction with the H 2 O pump loop 1 GPC off and on switch on panel L1. The GPC position enables the general-purpose computer to command the loop 1 pump, which is selected by the H2O pump loop 1 A or B switch, to circulate water through water coolant loop 1. The on position energizes the loop 1 pump. A ball-type check valve downstream of each water pump prevents reverse flow through the non-operating pump. The off position removes electrical power from both the A and B pumps of loop 1.

Water pump 2 is controlled by the H 2 O pump loop 2 GPC on, off switch on panel L1. When the switch is positioned to GPC , water pump 2 is commanded by the GPC to circulate water through water coolant loop 2. The on position energizes the water pump 2 to circulate water through water coolant loop 2. The off position removes electrical power from water coolant loop 2 pump.

Water loops 1 and 2 flow side by side through the same areas when both loop pumps are in operation. Downstream of the water pump in each loop, water flow splits into three parallel paths: one through the avionics bay 1 heat exchanger and cold plates; another through the avionics bay 2 heat exchanger and cold plates, payload bay floodlight cold plates and thermal conditioning of the crew cabin windows; and the third through the crew cabin multiplexer/demultiplexer flight deck cold plates, the avionics bay 3A heat exchanger and cold plates and avionics bay 3B cold plates. The three parallel paths in each coolant loop then rejoin.

The water coolant loops 1 and 2 flow toward the Freon-21 coolant loops 1 and 2 and water heat exchanger and split into two parallel paths. One parallel path in each water coolant loop flows through the Freon-21 coolant loops 1 and 2 and water interchanger, liquid-cooled garment heat exchanger, potable water chiller, cabin heat exchanger and IMU heat exchanger to the respective water coolant loop 1 and 2 pump. The other parallel path in each water coolant loop flows to a water coolant loop bypass in that loop.

The bypass controller in each water coolant loop is enabled by its corresponding H2O loop 1 and 2 bypass mode auto/man switch on panel L1. When a coolant loop's H 2 O loop bypass mode auto/man switch is positioned to auto , the water bypass controller and bypass valve automatically control the amount of water in the coolant loop that bypasses the water/Freon-21 coolant loop interchanger. When the bypass controller's outlet temperature is 65.5 F, the loop's bypass valve is fully closed, and the excess heat in the loop is transferred to the corresponding Freon-21 coolant loop at the coolant water interchanger. Cooled water flows through the LCG heat exchanger, cabin heat exchanger and IMU heat exchanger, which joins with the bypass flow parallel path. When the bypass controller senses that the coolant loop water pump's outlet temperature is 60.5 F, the controller bypasses a maximum amount of water around the Freon-21 coolant loop/water interchanger and allows the water at that coolant loop pump to be warmed from the parallel path of water flowing from the interchanger and corresponding LCG heat exchanger, cabin heat exchanger and IMU heat exchanger. When the H2O loop bypass mode auto/man switch for the coolant loop is positioned to man , the flight crew sets the corresponding H2O loop man incr/decr switch on panel L1 to manually control the bypass valve in that water coolant loop.

Because of changes in heat loads from the initial design, the water bypass controllers are not able to control temperatures automatically as originally intended. As a result, the water bypass control valve is manually controlled by the flight crew by positioning the H 2 O loop bypass mode auto/man switch in man and the H 2 O loop bypass man incr/decr switch for that water coolant loop on panel L1. The bypass valve is adjusted before launch to provide a flow of 900 to 1,000 pounds per hour through the Freon-21 coolant loop/water interchanger, and the control system remains in the manual mode for the entire flight.

The accumulator in each water coolant loop provides a positive pressure on the corresponding water pump inlet and accommodates thermal expansion and dampening pressure surges in that water coolant loop when the pump is turned on or off. Each accumulator is pressurized with gaseous nitrogen at 19 to 35 psi.

The pressure at the outlet of the water pump in each water coolant loop is monitored and transmitted to the H 2 O pump out press loop 1 and loop 2 switches on panel O1. When the switch is positioned to loop 1 or loop 2, the corresponding water coolant loop's pressure is monitored on the H 2 O pump out press meter on panel O1 in psia.

The yellow H2O loop C/W light on panel F7 will be illuminated if the outlet pressure of the water coolant loop 1 pump is below 45 psi or above 79.5 psi or if the outlet pressure of the loop 2 pump is below 45 psi or above 81 psi. The pump inlet and outlet pressure of each coolant loop is monitored and transmitted to the systems management GPC for CRT readout.

In summary, with the crew cabin's structural thermal capacity, its temperature will not exceed 95 F during entry or until flight crew egress.

ACTIVE THERMAL CONTROL SYSTEM

    The ATCS removes heat from the ARS at the water coolant loop/Freon-21 coolant loop interchanger and from each of the fuel cell power plant heat exchangers and warms the PRSD cryogenic oxygen in the ECLSS oxygen supply line and the hydraulic fluid systems at the hydraulic heat exchanger. The ATCS consists of two complete and identical Freon-21 coolant loop systems; cold plate networks for cooling avionics units; liquid/liquid heat exchangers; and three heat sink systems-radiators, flash evaporator and ammonia boiler.

    During ground operations (checkout, prelaunch, and post landing), orbiter heat rejection is provided by the GSE heat exchanger in the Freon-21 coolant loops through ground system cooling.

    From lift-off to an altitude of less than 140,000 feet-approximately 125 seconds-thermal lag is used. Approximately 125 seconds after lift-off, the flash evaporator subsystem is activated and provides orbiter heat rejection of the Freon-21 coolant loops via water boiling. Flash evaporator operation continues until the payload bay doors are opened in orbit.

    When the payload bay doors are opened, radiator panels attached to the forward payload bay doors may or may not be deployed depending on the flight. If deployed away from the payload bay doors, the forward two panels on each side of the orbiter will radiate from both sides. If not deployed, they will radiate only from one side. The aft radiator panels on the forward portion of the aft payload bay doors are affixed to the doors and radiate only from the upper surface. On-orbit heat rejection is provided by the radiator panels; however, during orbital operations when a combination of heat load and spacecraft attitude exceeds the capacity of the radiator panels, the flash evaporator subsystem is automatically activated to meet total system heat rejection requirements.

    At the conclusion of orbital operations, the flash evaporator subsystem is activated, and the payload bay doors are closed with the radiator panels retracted, if they were deployed, in preparation for entry.

    The flash evaporator subsystem operates during entry to an altitude of 100,000 feet, at which point boiling water can no longer provide adequate Freon-21 coolant temperatures. Through the remainder of the entry phase and after landing until ground cooling is connected, heat rejection of the Freon-21 coolant loops is provided by the evaporation of ammonia through the use of the ammonia boilers. When ground cooling is initiated after landing, the ammonia boilers are shut down, and heat rejection of the Freon coolant loops is provided by the GSE heat exchanger.

    Each Freon-21 coolant loop has a pump package consisting of two pumps and an accumulator. One Freon-21 coolant pump in each coolant loop is active at all times. The metal bellows-type accumulator in each coolant loop is pressurized with gaseous nitrogen to provide a positive suction pressure on the pumps and permit thermal expansion in that coolant loop. A ball check valve downstream of the pumps in each coolant loop prevents a reverse flow through the non-operating pump in the loops. The Freon pumps in each Freon coolant loop are controlled individually by the Freon pump loop 1 and loop 2 switches on panel L1. When either switch is positioned to A or B, the corresponding Freon pump in that loop operates. The off position of each switch prohibits either Freon pump in that coolant loop from operating.

    When a Freon coolant pump is operating, Freon is routed in parallel through the three fuel cell heat exchangers and the midbody cold plate network to cool electronic avionics units. The Freon coolant reunites in a series flow path before entering the hydraulics heat exchanger. It then extracts energy from the Freon-21 coolant loop to heat hydraulic system fluid during on-orbit hydraulic circulation thermal-conditioning operations. During the prelaunch and boost phase of the mission and during the atmospheric flight portion of entry through landing and rollout, the hydraulic system heat exchanger transfers excess heat from the hydraulic systems to the Freon-21 loops. The Freon flows from the hydraulic fluid heat exchanger to the radiators, which are bypassed through a bypass valve during ascent and entry because the payload bay doors are closed. The radiators are located on the underside of the payload bay doors. When the payload bay doors are opened in orbit, the radiators are used for heat rejection to space. The Freon coolant flows through the GSE heat exchanger, ammonia boilers and flash evaporator. It is then divided into two parallel paths. One path flows through the ECLSS oxygen restrictor to warm the PRSD oxygen for the ECLSS to 40 F. It then flows through a flow-proportioning valve into parallel paths to the payload heat exchanger and ARS interchanger and returns to a series flow. The other path flows through aft avionics bays 4, 5 and 6 to cool some electronic avionics equipment in each avionics bay. It also flows through cold plates to cool rate gyro assemblies 4, 3, 2 and 1 and then returns to a series flow. The parallel paths return in series to the Freon coolant pump in that Freon coolant loop.

    The Freon-21 coolant pumps, ARS interchanger, three fuel cell power plant heat exchangers, payload heat exchanger, flow-proportioning valve modules and midbody cold plates are located in the lower forward portion of the midfuselage. The radiators are attached to the underside of the payload bay doors. The cold plates for the hydraulic system heat exchangers; ground support equipment heat exchanger; ammonia boilers; flash evaporator; and aft avionics bays 4, 5 and 6 are located in the aft fuselage of the orbiter. The radiator flow control assemblies and RGAs are located in the lower aft portion of the midfuselage.

    The radiator system consists of three radiator panels for a baseline mission configuration under the right and left payload bay doors. During ascent and entry the radiator panels are secured to the payload bay doors. The two radiator panels attached to the forward right and left payload bay doors are deployable from the forward payload bay doors when the doors are opened on orbit. The heat rejection requirements of the orbiter for a specific mission will determine if the forward radiators are to be deployed. The third radiator panel is fixed to the forward underside of the aft right and left payload bay doors and is not deployable. The baseline radiator panels are designed for missions requiring heat rejection of 21,500 Btu per hour. A fourth radiator panel, which is deployable, may be required for a specific mission and would be fixed to the aft underside of the aft right and left payload bay doors. With the addition of the fixed fourth radiator panel, the heat rejection capability is 29,000 Btu per hour. When the payload bay doors are closed, the radiators are bypassed.

    The deployable radiators are secured to the right and left payload bay doors by six motor-operated latches. When the payload bay doors are opened on orbit and the mission dictates that the deployable radiators be deployed, the six motor-driven latches unlatch the radiators from the payload bay doors, and the motor-driven torque-tube-lever arrangement deploys the forward radiators at 35.5 degrees from the payload bay doors. The forward radiators would then provide heat rejection from both sides of the radiator panels.

    The aft fixed radiator panels are attached to the payload bay doors by a ball joint arrangement at a maximum of 12 locations to compensate for movement of the payload bay door and radiator panel caused by the thermal expansion and contraction of each member.

    The radiator panels are constructed of an aluminum honeycomb face sheet 126 inches wide and 320 inches long. The forward deployable radiator panels are two-sided and have a core thickness of 0.9 of an inch. They have longitudinal tubes bonded to the internal side of both face sheets. Each of the forward deployable panels contains 68 tubes spaced 1.9 inches apart. Each tube has an inside diameter of 0.131 of an inch. Each side of the forward deployable radiator panels has a coating bonded by an adhesive to the face sheet consisting of silver-backed Teflon tape for proper emissivity properties. The aft fixed panels are one-sided, and their cores are 0.5 of an inch thick. They have tubes only on the exposed side of the panel and a coating bonded by an adhesive to the exposed face sheet. The aft panels contain 26 longitudinal tubes spaced 4.96 inches apart. Each tube has an inside diameter of 0.18 of an inch. The additional thickness of the forward radiator panels is required to meet deflection requirements when the orbiter is exposed to ascent acceleration.

    The radiator panels on the left and right sides are configured to flow in series, while flow within each panel is parallel through the bank of tubes connected by an inlet and outlet connector manifold. The radiator panels on the left side are connected in series with Freon-21 coolant loop 1. The radiator panels on the right side are connected in series with Freon-21 coolant loop 2.

    If the two deployable and two fixed radiators are installed on the payload bay doors, the radiator panels will provide an effective heat dissipation area of 1,195 square feet on orbit. Each radiator panel is 10 feet wide and 15 feet long. The Freon tubing in the radiator panels is more than 1 mile long.

    A radiator flow control valve assembly in each Freon coolant loop controls the temperature of that loop through the use of the variable flow control, which mixes hot bypassed Freon coolant flow with the cold Freon coolant from the radiators. The radiator flow control valve assemblies can be controlled automatically or manually by the flight crew.

    In the automatic operation the rad controller loop 1 and loop 2 auto A, off, auto B switch on panel L1 is positioned to auto A or auto B to apply electrical power to the corresponding radiator flow controller assembly. The rad controller loop 1 and loop 2 mode auto , man switch on panel L1 is positioned to auto, and the rad controller out temp switch on panel L1 is positioned to norm or hi. With the rad controller out temp switch on panel L1 in norm , the radiator outlet temperature in Freon coolant loops 1 and 2 is automatically controlled at 38 F; in hi, the temperature is automatically controlled at 57 F. It should be noted that the flash evaporator is activated automatically when the radiator outlet temperature exceeds 41 F to supplement the radiators' ability to reject excess heat.

    The radiator talkback indicator next to the rad controller loop 1 and loop 2 auto A , off and auto B switches on panel L1 indicates the position of the bypass valve in that Freon coolant loop. The indicator indicates byp when the bypass valve in that Freon coolant loop is in the bypass position, barberpole when the motor-operated bypass valve is in transit and rad when the bypass valve is in the radiator flow position.

    When the rad controller loop 1 and loop 2 mode auto , man switch on panel L1 is positioned to man for the Freon coolant loop selected, the automatic control of the radiator flow control valve assembly in that loop is inhibited; and the flight crew controls the flow control valve assembly manually using the rad controller loop 1 , loop 2, rad flow and bypass switches on panel L1. When the switch is positioned to bypass , the loop's motor-operated bypass valve permits that Freon coolant loop to bypass the radiators. When the switch is positioned to rad flow, the valve permits coolant to flow through the radiators. The rad controller loop 1 and 2 talkback indicator for the Freon coolant loop indicates byp when the bypass valve in that loop is in bypass and barberpole when it is in transit.

    The flash evaporators reject heat loads from Freon-21 coolant loops 1 and 2 during ascent above 140,000 feet and supplement the radiators on orbit if required. They also reject heat loads during deorbit and entry to an altitude of approximately 100,000 feet.

    The flash evaporators are located in the aft fuselage of the orbiter. There are two evaporators in one envelope. One is the high-load evaporator; the other is the topping evaporator. There are two major differences between the evaporators. The high-load evaporator has a higher cooling capacity than the topping evaporator, and its overboard vent is only on the left side. The topping evaporator vents steam equally to the left and right sides of the orbiter, which is non-propulsive. The evaporators are cylindrical and have a finned inner core. The hot Freon-21 from the coolant loops flows around the finned core, and water is sprayed onto the core by water nozzles from either evaporator. The water vaporizes, cooling the Freon-21 coolant loops. In the low-pressure atmosphere above 100,000 feet, water vaporizes quickly. Changing water liquid to vapor removes approximately 1,000 Btu per hour per 1 pound of water. The water for the evaporators is obtained from the potable water storage tanks through water supply systems A and B.

    The flash evaporators have three controllers. The primary A controller has two separate, functionally redundant shutdown logic paths (undertemperature rate of cooling). Primary B has a single shutdown logic path; secondary has no shutdown. The flash evaporator controllers are enabled by the flash evaporator controller switches on panel L1. The flash evap controller pri A switch controls controller A, the pri B switch controls controller B, and the sec switch controls the secondary controller. When the pri A , pri B or sec switch is positioned to GPC, the corresponding controller is turned on automatically during ascent by the backup flight system computer as the orbiter ascends above 140,000 feet. During entry the BFS turns the corresponding controller off as the orbiter descends to 100,000 feet. The on position of the switch provides electrical power directly to the corresponding flash evaporator controller. The off position of the switch removes all electrical power and inhibits flash evaporator operation.

    The primary A controller controls water flow to the flash evaporator from water supply system A through water feed line A. The primary B controller controls water flow to the flash evaporator from water supply system B through water feed line B. Note that when a primary controller is enabled, both evaporators can be used simultaneously.

    The secondary controller controls water flow to the flash evaporator from water supply system A through feed line A if the flash evaporator controller sec A sply switch on panel L1 is in the sply A position and if the hi load evap switch on panel L1 is in the enable position. If the sec B sply switch is in the sply B position and the hi load evap switch is in the enable position, the secondary controller controls water flow to the flash evaporator from water supply system B through feed line B. When the secondary controller is used and the hi load evap switch is off , both the A and B water supply systems will feed the topping evaporator in an alternate pulsing fashion. When the secondary controller is used and the hi load evap switch is in the enable position, the topping evaporator is disabled.

    The primary A and B controllers modulate the water spray in the evaporator to control the Freon-21 coolant loops' evaporator outlet temperature at 39 F. The secondary controller modulates the water spray in the evaporator to control the Freon-21 coolant loops' evaporator outlet temperature at 62 F. The temperature sensors are located at the outlets of both evaporators.

    The applicable flash evaporator controller pulses water into the evaporators, cooling the Freon-21. The steam generated in the topping evaporator is ejected through two sonic nozzles at opposing sides of the orbiter aft fuselage to reduce payload water vapor pollutants on orbit and to minimize venting thrust effects on the orbiter's guidance, navigation and control system. The high-load evaporator is used in conjunction with the topping evaporator during ascent and entry when higher Freon-21 coolant loop temperatures impose a greater heat load that requires a higher heat rejection. The hi load evap switch on panel L1 must be in the enable position for high-load evaporator operation. After leaving the high-load evaporator, Freon-21 flows through the topping evaporator for additional cooling. The steam generated by the high-load evaporator is ejected through a single sonic nozzle on the left side of the orbiter aft fuselage. The high-load evaporator would not normally be used on orbit because it has a propulsive vent and might pollute a payload.

    Each primary controller has an automatic shutdown capability to protect the evaporator from over- or undertemperature conditions. The evaporator's outlet temperature is monitored to determine if a thermal shutdown of the evaporator is warranted. If the evaporator's outlet temperature goes below 37 F for 20 seconds or more, an undertemperature shutdown of the evaporator occurs. If the evaporator outlet temperature is greater than 41 F for 40 seconds, an overtemperature shutdown of the evaporator occurs. If the evaporator is shut down because it is over- or undertemperature, electrical power to the affected controller must be recycled to re-enable operations. The secondary controller does not have any automatic shutdown capability.

    The evaporator outlet temperature of Freon-21 coolant loops 1 and 2 is transmitted to panel O1. When the Freon loop 1 or 2 switch on panel O1 is positioned to loop 1 or 2 , the evaporator outlet temperature of Freon coolant loops 1 or 2 can be monitored on the Freon evap out temp meter on panel O1 in degrees Farenheit. If the outlet temperature drops below 32 F or rises above 60 F, the red Freon loop C/W light on panel F7 will be illuminated.

    The flash evaporator topping evaporator can be used to dump excess potable water from the potable water storage tanks, if required, on orbit. The radiator flow control valve assembly has an alternate control temperature of 57 F that is used for this excess water dump into the topping evaporator.

    Electrical heaters are employed on the topping and high-load flash evaporators' steam ducts to prevent freezing. The flash evap hi load duct htr rotary switch on panel L1 selects the electrical heaters. Switch positions A and B provide electrical power to the corresponding thermostatically controlled heaters on the high-load evaporator steam duct and steam duct exhaust. The A/B position provides electrical power to both thermostatically controlled heaters. The C position provides electrical power to the thermostatically controlled C heaters. The off position removes electrical power from all the heaters.

    The flash evap topping evaporator duct rotary switch on panel L1 selects the thermostatically controlled electrical heaters on the topping evaporator. Positions A and B provide electrical power to the corresponding heaters, while A/B provides electrical power to both A and B heaters. The C position provides power to the C heaters. The off position removes electrical power from all the heaters.

    The topping evaporator's left and right nozzle heaters are controlled by the topping evaporator heater l and r switches on panel L1. When the left and right switches are positioned to auto A or auto B, electrical power is provided to the corresponding left and right nozzle heaters, and the corresponding nozzle temperature is maintained between 40 and 70 F. The off position removes electrical power from both heater systems.

    The ammonia boilers use the low boiling point of ammonia to cool the Freon-21 coolant loops when the orbiter is below 100,000 feet during entry. There are two complete, individual ammonia storage and control systems that feed one common boiler containing ammonia passages and the individual Freon-21 coolant loops 1 and 2.

    Each ammonia boiler storage tank contains a total of 49 pounds of ammonia, all of which may be used for cooling. Each ammonia tank is pressurized with gaseous helium at an operating pressure between 550 psia to 83 psia. Downstream of each ammonia storage tank to the common boiler are three control valves: a normally closed isolation valve, a normally open secondary control valve and a primary control valve. A relief valve in each ammonia boiler storage system provides overpressurization protection of that ammonia storage tank.

    Ammonia boiler supply systems A and B are enabled by the corresponding NH3 controller A and B switches on panel L1.

    When the NH3 controller A switch is positioned to pri/GPC before entry, it enables the computer to control electrical power to the primary and secondary controller within ammonia controller A. When the orbiter descends through 100,000 feet, the backup flight system computer commands the ammonia system A controller on. The primary controller in the ammonia system A controller energizes the ammonia A system isolation valve open, permitting ammonia to flow to two motor-operated controller valves and commands the primary motor-operated valve to regulate the flow to the ammonia boiler. Three temperature sensors are located on each Freon-21 coolant loop. One sensor on each Freon-21 coolant loop is associated with the primary controller and its motor-operated valve to regulate ammonia system A flow to maintain Freon-21 coolant loop 1 and 2 temperatures at the outlet of the ammonia boiler at 34 F. One sensor on each Freon-21 coolant loop is associated with the ammonia system A controller fault detection logic. If the Freon-21 coolant loop 1 and 2 temperatures drop below 31 F for greater than 10 seconds, the fault detection logic automatically inhibits the primary controller, which removes power from the ammonia system A isolation valve and the primary controller's motor-operated valve. The fault detection logic switches to the secondary controller in the ammonia system A controller, which energizes a redundant coil in the ammonia system supply A isolation valve. It opens the valve and commands the primary motor-operated valve to full open and allows the secondary controller to control the secondary motor-operated valve to regulate the ammonia A flow to the ammonia boiler. The third sensor on each Freon coolant loop is associated with the secondary controller and secondary motor-operated valve. It regulates ammonia supply system A flow to maintain the Freon-21 coolant loop 1 and 2 temperatures at the outlet of the ammonia boiler at 34 F. This automatic switchover is only from the primary to the secondary.

    The ammonia boiler is a shell-and-tube system with a single pass of ammonia on the ammonia side and two passes of each Freon-21 coolant loop through the boiler. The ammonia flows in the ammonia tubes and the Freon-21 coolant loop flows over the tubes, cooling the Freon-21 coolant loops. When the ammonia is sprayed on the Freon-21 coolant lines in the boiler, it immediately vaporizes, and the heat and boiler exhaust is vented overboard in the upper aft fuselage of the orbiter next to the bottom right side of the vertical tail. The ammonia boiler operations continue through the remainder of entry, landing and rollout until a ground cooling cart is connected to the GSE heat exchanger.

    When the NH3 controller A switch is positioned to sec/on, the ammonia system A controller is electrically powered and enabled directly (no computer command is required). The primary controller in the ammonia system A controller energizes the system's isolation valve open, permitting ammonia to flow to two motor-operated controller valves. The primary controller commands the secondary controller's motor-operated valve to the open position and the primary controller's motor-operated valve to regulate the ammonia flow to the ammonia boiler. The three temperature sensors on each Freon-21 coolant loop operate and control Freon-21 coolant loop 1 and 2 temperature in the same manner as in the primary/GPC mode. The fault detection logic also operates in the same manner as in the primary/GPC mode.

    The off position removes all electrical power from the ammonia system A controller, rendering ammonia system A inoperative.

    The NH3 controller B switch controls the ammonia system B controller and ammonia supply system B in the same manner as the ammonia system A controller and ammonia supply system A are controlled by the A switch.

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.

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.

WASTE WATER TANK

    A single waste water tank receives waste water from the ARS humidity separator and the waste collection system. The tank is located beneath the crew compartment middeck floor next to the potable water tanks.

    The waste water tank holds 165 pounds, is 35.5 inches long and 15.5 inches in diameter, and weighs 39.5 pounds dry. It is pressurized by gaseous nitrogen from the same source as the potable water tanks.

    Waste water is directed to the waste water tank 1 inlet valve, which is controlled by the waste H 2 O tank 1 switch on panel ML31C. When the switch is positioned to open , waste water is directed to the waste water tank. 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 switch positioned to off closes the waste water tank inlet, isolating the waste water tank from the waste water collection system. When the valve is open, waste water from the tank can also be directed to the waste water dump for overboard dumping.

    The waste water dump isolation valve and waste water dump valve in the waste water dump line allow waste water to be dumped overboard through the waste water dump. The waste H 2 O dump isol valve switch on panel ML31C positioned to open allows waste water to be directed to the waste water dump valve. A talkback indicator above the waste H2O dump isol valve switch indicates op when the valve is open, barberpole when the valve is in transit and cl when the valve is closed.

    In order for waste water to be dumped overboard, the waste water dump valve must be opened. It is controlled by the waste H 2 O dump valve enable/nozzle heater switch and the waste H 2 O dump valve switch on panel ML31C. When the waste H 2 O dump valve enable/nozzle heater switch is positioned to on , electrical power is supplied to the waste water dump heaters and the waste H 2 O dump valve switch. When the waste H 2 O dump valve switch is positioned to open, the dump valve allows waste water to be dumped overboard. A talkback indicator above the dump switch indicates op when the valve is open, barberpole when the valve is in transit and cl when the valve is closed. If waste water is dumped overboard, the dump isolation valve switch is positioned to cl upon completion of the dump. The waste H2O dump valve is positioned to cl , and the waste H2O dump valve enable/nozzle heater switch is set to off . (If the heater switch is positioned to off before the dump valve switch is positioned to close, the dump valve will remain open.) The heaters at the waste water dump prevent waste water from freezing at the overboard dump.

    The waste water dump line, upstream of the waste dump nozzle, has electrical heaters on the line to prevent waste water from freezing. The A and B heaters are powered by the H 2 O line htr A and B circuit breakers on panel ML86B and are thermostatically controlled. (These circuit breakers also provide power to thermostatically controlled heaters on the supply water line and waste collection system vacuum vent line.)

    The contingency crosstie quick disconnect in the waste water overboard dump line between the dump isolation valve and dump valve permits waste water to be joined with the supply water system through a flexible hose for emergency dumping of supply water through the waste water dump or using waste water for the flash evaporators.

    The waste water tank 1 drain valve controls the draining of the waste water tank during ground operations through the ground support equipment flush and drain. When the waste H 2 O drain tank 1 valve switch on panel ML31C is positioned to open , the valve permits the draining and flushing of the waste water tank. The drain line is capped during flight. A talkback indicator above the switch indicates op when the valve is open, barberpole when the valve is in transit and cl when the valve is closed.

    Personal hygiene accommodations for flight crew members include personal hygiene kits, pressure-packed personal hygiene agents and towel tissue dispensers. The personal hygiene kits have provisions for tooth brushing, hair care, shaving, nail care, etc. The pressure-packaged personal hygiene agents are for cleaning the hands, face and body.

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    Last Updated Wednesday January 12 09:54:36 EDT 1994
    Jim Dumoulin (dumoulin@titan.ksc.nasa.gov)



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