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Methods of Water Management, Water Recovery, and Quality Monitoring

  • Scott RitterEmail author
Living reference work entry

Abstract

To address the water needs of crew members, several methods for water management, recovery, and quality monitoring have been developed for manned space missions. This chapter provides an overview of these methods and their evolution across the manned spaceflight programs.

Keywords

Water management Water recovery Water quality Humidity condensate Urine distillation Fuel cells Biocide Life support systems 

Introduction

In one day, a 75 kg (165 lb) person requires approximately 3.6 kg (7.9 lb) of potable water (e.g., for drinking and preparing food) and 26 kg (57 lb) of hygiene water (e.g., for showers, sink, toilet flushing, laundry, and washing dishes) (Eckart 1994; Schubert et al. 1984). Over one year, this amounts to approximately 1,300 kg (2,866 lb) of potable water and 9,490 kg (20,922 lb) of hygiene water, or 10,790 kg (23,788 lb) in total. To address this need, numerous methods for water management, recovery, and quality monitoring have been developed for manned space missions (Table 1). During the early manned space missions, crews relied entirely on consumables for water management, which were designed to be discarded after use. Over time, these expendable technologies evolved to include regenerative systems, which allow for easy maintenance, component replacement, reduced resupplies, in situ quality monitoring, and minimal mass, volume, and power consumption. These technologies, and their iterative evolution, have enabled space missions of incrementally longer duration, larger crew size, and reduced resupply and waste return cost. Reducing these costs (approximately $50,000/L ($10,000/lb)) by improving water recovery and monitoring systems are critical constraints for future long-duration space missions (Czupalla et al. 2004; NASA Facts 2008).
Table 1

Evolution of space program water management strategies

Program

Potable water

Storage

Wastewater

Condensate

Microbial control

Quality monitoring

Mercury

Ground launched and stored

Tank with flexible bladder

Vented to space

Vented to space

Residual disinfectant (chlorine) in the Cocoa Beach, Florida, public water supply

None

Gemini

Ground launched and stored

Tank with pressurized bladder

Vented to space

Vented to space

Chlorine biocide

Pre- and postflight

Apollo Command Module

Fuel cell byproduct water

Tank with pressurized bladder

Vented to space

Stored for cooling, vented excess

Chlorine biocide injected every 24 h

Pre- and postflight

Apollo Lunar Module

Ground launched and stored

Tank with pressurized bladder

Stored (no lunar dumping allowed)

Stored (no lunar dumping allowed)

Iodine biocide

Pre- and postflight

Skylab

Ground launched and stored

Pressurized steel tank

Stored, vented when full

Vented to space

Iodine biocide injection

Iodine sampler

Space Shuttle

Fuel cell byproduct water

Pressurized steel tank

Stored

Stored

Iodine biocide

On orbit pH

Vostok

Ground launched and stored

Two-layer container in a hermetically sealed metal cylinder

Vented to space

Vented to space

Water boiled prelaunch, silver biocide added

Pre- and postflight

Voskhod

Ground launched and stored

Two-layer container in a hermetically sealed metal cylinder

Vented to space

Vented to space

Water boiled prelaunch, silver biocide added

Pre- and postflight

Soyuz

Ground launched and stored

Two-layer container in a hermetically sealed metal cylinder

Vented to space

Vented to space

Water boiled prelaunch, silver biocide added

Pre- and postflight

Salyut

Ground launched and recovered from condensate

Rodnik “spring” tank system

Stored, vented when full

Recovered

Water heated, silver biocide added

Pre- and postflight

Mir

Ground launched and recovered from condensate

Tanks with pressurized bladders

Urine recovered for oxygen generation, hygiene water recovered for hygiene reuse

Recovered

Water heated, silver biocide added

On orbit pH and salinity

Shenzhou

Ground launched and stored

Pressurized steel tank

Vented to space

Vented to space

Silver biocide added

Pre- and postflight

Tiangong

Ground launched and stored

Pressurized steel tank

Stored, vented when full

Vented to space

Silver biocide added

Pre- and postflight

ISS

Majority recovered, some ground launched

Metal bellows with supply and delivery pumps (USA), tanks with pressurized bladders (Russia)

Recovered

Recovered

Iodine biocide and heat sterilization (USA), silver biocide (Russia)

On orbit and ground monitoring

Early Manned Missions

Methods for water management, recovery, and quality monitoring in space were first studied and developed by the US Air Force in the 1950s. In 1952, the US Air Force designed a sealed chamber for space medicine research that duplicated all aspects of life inside a spacecraft, except weightlessness. This chamber, called the “space cabin simulator,” had environmental control systems, included a system for urine distillation and recycling with air moisture to provide drinking water. From 1956 to 1958, isolation tests were successfully conducted in the chamber, and these tests gradually increased in duration from 24 h to 1 week. However, cost, weight, and design constraints meant that these methods would not be used in spacecraft until decades later (Swenson et al. 1998).

During the planning stages of Project Mercury (1959–1960), it was estimated that perspiratory and respiratory water production within the space capsule could amount to 2.7–3.2 kg (6–7 lb) per day. So, mission planners designed a water separator system (Fig. 1) to remove water vapor from perspiration and respiration and store it in a condensate tank for later disposal or venting to space (Swenson et al. 1998; Hubbard 1959). Throughout the Project Mercury manned spaceflight period (1961–1963), 2.7 kg (6 lb) of ground-launched drinking water was supplied to each astronaut for each of the six manned missions to space. These six pounds of drinking water were divided into two flexible pouches, which were fitted to flexible hoses that led to a drinking tube. Squeezing the flexible pouches drew the water into the tube for drinking. This simple “fill and draw” system was used because the first three manned Mercury missions were short (i.e., 15 min to 4 h) and primarily concerned with achieving short duration space entry and orbit. Astronauts on the subsequent, longer duration 9- and 34-hour Mercury 8 and 9 missions required more ground-launched water and could use the recovered water in the condensate tank as backup. Urine and condensate water samples began to be collected for ground testing during the last Mercury mission, in which Gordon Cooper spent 34 h completing 22 orbits (Sauer and Calley 1975; Swenson et al. 1998).
Fig. 1

Mercury capsule water separator (Hubbard 1959)

Gemini (1964–1966) was the first manned space program to use fuel cells for spacecraft electricity generation. Fuel cells use gaseous hydrogen and oxygen to produce electricity, with water as the byproduct. Considerable effort was made to treat this byproduct water with filtration, carbon sorption, and ion exchange resins to achieve potable water quality standards. However, there were water acidity problems, despite these efforts. Consequently, a fill and draw system similar to that used during Project Mercury was used as backup. Additionally, ground-launched water was also supplied to the spacecraft cooling system, for contingency situations, along with humidity condensate. This interconnectedness of the ground-launched water and humidity condensate systems introduced a risk of microbial contamination. Therefore, chlorine was added to ground-launched water as a biocide to minimize this hazard. A schematic of the Gemini water management system is shown in Fig. 2 (Grimwood and Hacker 1969; Sauer and Calley 1975).
Fig. 2

Gemini 8 water management system (Gemini 1966)

The Apollo Program (1966–1972) resolved the fuel cell water quality problems associated with Gemini, and fuel cell water subsequently became the primary source of drinking and hygiene water in the Apollo Command Module (Fig. 3). This resolution was reached by replacing Gemini’s organic electrodes with sintered nickel electrodes, which produced high quality water because they did not degrade. Fuel cell water was then routed to the potable water tank, or if full, the wastewater tank. From the potable water tank, water was routed to either the food preparation unit (after passing through a heater) or the drinking water gun (after passing through a chiller). Humidity condensate from the cabin atmosphere and the crew’s pressure suits was also sent to the wastewater tank, and excess wastewater was dumped overboard. Similar to Gemini, chlorine was added to the potable water system to minimize risk of microbial contamination (Sauer and Calley 1975).
Fig. 3

Apollo Command Module water system (Sauer and Calley 1975)

Altogether, the functional components of the Apollo command module water management system included: (1) aluminum potable water tank with 16 kg (36 lb) water capacity; (2) aluminum wastewater tank with 25 kg (56 lb) capacity; (3) water chiller of 227 g (0.5 lb) capacity and temperature reduction of 298 to 280 K (76 to 45 °F), and water heater of 1.1 kg (2.5 lb) capacity and temperature increase of 289 to 341 K (60 to 154 °F); (4) food preparation unit, which dispensed water in 28 g (1 oz) aliquots into dehydrated food and beverages using two valves (hot or cold) and one nozzle, similar to the water gun; (5) drinking water gun with a 178 cm (70 in) flexible synthetic rubber hose, and a dispense volume of 14 g (0.5 oz) per activation; and (6) aluminum transfer lines of 0.64 cm (0.25 in) diameter (Sauer and Calley 1975).

In contrast to the Apollo Command Module, the Apollo Lunar Module was supplied by batteries instead of fuel cells and therefore used ground-launched water stored in tanks for drinking and hygiene, similar to Gemini (Fig. 4). Water was stored in three tanks: a 151 kg (332 lb) tank for descent during lunar orbit and lunar surface exploration and two 19 kg (42 lb) tanks for ascent, rendezvous, and linkup phases. The module’s cooling system used the potable water supply to sublimate ice to the space vacuum using a sintered nickel plate. To prevent blockage of the pores in this plate, ground-launched water was distilled to remove impurities. In addition, to prevent operating problems with the sublimation units and to disinfect the lunar module’s potable water supply, chlorine disinfectant was replaced with iodine to reduce the chance of unforeseen reactivity (Sauer and Calley 1975).
Fig. 4

Apollo Lunar Module water system (Sauer and Calley 1975)

Chemical and microbial water quality on both the Apollo Command and Lunar Modules was tested pre- and postflight for contamination. The only potential contaminant was ionic nickel, which was found to have originated from the nickel brazing material used in constructing the hot water heater. Although the levels were not medically significant for the short duration missions of Apollo, it was determined that the heater would need a redesign for longer duration missions (Sauer and Calley 1975).

During the Apollo 13 mission, the loss of service module systems resulted in the inability of the fuel cells to produce drinking water. The lunar module contained approximately 150 L (40 gal) of water; however, most of it was needed by the sublimators to cool critical equipment. Therefore, lunar module water was rationed for drinking by the crew from the usual 1 L (34 oz) per day to approximately 0.20 L (6.7 oz) per day. This extraordinary water conservation effort helped the crew overcome off nominal mission difficulties and contributed to their survival (Jones and Glover 1995).

The Vostok (1961–1963), Voskhod (1964–1965), Soyuz (1967–1991), Shenzhou (1999–2016), and Tiangong programs managed water in similar ways to Mercury, Gemini, and the Apollo Lunar Module. Potable water was ground-launched and stored in hermetically sealed pressurized tanks. Wastewater was stored or vented to space and not recovered for reuse. Prelaunch water was boiled and a silver biocide was added to control microbial growth (Daues 2016; Seedhouse 2010).

Early Space Stations

The Skylab Program (1973–1974), which focused on long-duration missions, relied heavily on resupplied consumables, using ground-launched water with no wastewater recovery for each of its three missions of 28, 59, and 84 days. However, Skylab did introduce new methods for in situ monitoring of iodine biocide levels in the water supply and storage of urine samples in a freezer for later analysis on Earth. Throughout Mercury, Gemini, and Apollo, astronauts maintained hygiene using sponge baths. But NASA wanted Skylab to feel more like a home, particularly because astronauts were there for long durations. Thus, NASA developed a shower for Skylab (Fig. 5). This shower consisted of a cylindrical cloth bag, in which crew members squirted warm water on themselves and scrubbed with liquid soap. This system required that the other crew members vacuum up the water that had escaped into the surrounding air and equipment. This process – both for the showering crew member and the other crew members cleaning up – proved time consuming, plus the free floating water inside the cabin that was created by this shower system posed risks to equipment and crew health. Therefore, sponge baths were reintroduced for subsequent NASA missions and will likely continue to be used for future Deep Space and Mars missions (Wong 2017).
Fig. 5

Skylab 2 Commander, Charles “Pete” Conrad using the shower facility (NASA 1973)

The Salyut (1971–1986) and Mir (1986–2000) programs demonstrated a variety of effective systems, with abilities to collect, process, store, and recycle water produced and used by crew in the sink, shower, toilet, and air condensation (Czupalla et al. 2004). Similar to the Skylab program, the Salyut program also included a shower on several space station iterations. But unlike Skylab, Salyut supplied the crew with both ground launched water and regenerated water from atmospheric humidity condensate. This condensate recovery process was later used on Mir, in addition to recovery of hygiene water through a system of filters, activated charcoal, and ion exchange resins, for reuse as hygiene water only. Recovery of condensate and wastewater was also used to feed an oxygen generation system, called the Elektron System. This system used electrolysis to split liquid water into hydrogen and oxygen gas. The oxygen gas was supplied back to the cabin atmosphere for breathing and the hydrogen was off-gassed into space as waste (McCoy 2012; Yeoman et al. 2009). A shower, similar to those used in Skylab and Salyut, was also featured on Mir; however, the shower, in combination with high cabin humidity (caused by several power outages), allowed for the proliferation of microbes within the spacecraft due to an abundance of condensed water globules. This resulted in the need to develop in situ water quality tests to more quickly determine the presence of microbes harmful to human health (Bell 2007). Both the Elektron System and in-situ water quality tests developed on Mir have since been adapted for use on the International Space Station (Fig. 6). Otherwise, the Mir program relied largely on resupplied consumables for its potable water supply, which resulted in water transfer becoming one of the major activities that occurred during Mir dockings with the Space Shuttle (Daues 2016).
Fig. 6

Replacing the Elektron System on the International Space Station (NASA 2011)

Space Shuttle

The Space Shuttle program (1981–2011) also relied heavily on resupplied consumables but continued the Apollo program practice of using fuel cells to generate power and onboard drinking/hygiene water. Three fuel cell power plants, which generated up to 11.3 kg (24.9 lb) of potable water per hour, were installed on the space shuttles. Fuel cell water was directed to four potable water tanks, each with a 75 kg (165 lb) water capacity. Water entering the storage tanks passed through a microbial filter that added iodine to the water to prevent microbial growth. Wastewater was fed from the crew cabin humidity separator and from the crew to a similarly sized wastewater tank. In situ water pH sensors were installed on the water outlet of the water relief panel to ensure portability. Up to 85% of excess hydrogen was removed from fuel cell water with hydrogen separators that vented hydrogen overboard (Dismukes 2002).

International Space Station

Beginning with its first crew in 1998 through November 2008, the International Space Station (ISS) received all of its drinking and hygiene water from Earth, and its wastewater was stored and returned to Earth for disposal. The US crew’s water was launched from the USA and used an iodine residual disinfectant like the Space Shuttle, while the Russian crew’s water was launched from Kazakhstan and used a silver residual disinfectant. Wastewater – from urine, urine flush, sink, shower, toilet, pretreatment, water processor distillate and brine, medical water, and water from flight experiments and science samples – was collected, stored, and returned to earth for disposal. At a launch cost of approximately $4,227/L ($16,000/gal), this groundwater resupply strategy proved costly, limited crew size, and limited mission duration, so a new water recovery system to alleviate these constraints was developed (Barta 2017).

This new Water Recovery System (WRS) was developed to minimize expendable materials by using regeneration when possible, recover as much mass as possible, minimize redundancy, and minimize risk of failure (Fig. 7). US water recovery called for recovered urine to be combined with all other waste waters and processed to potable specifications for reuse in all applications, with in situ quality monitoring of conductivity, pH, iodine, and total organic carbon, and samples returned to earth for measurement of microorganisms, total organic carbon, and ions. Russian water recovery called for separate recovery of condensate (with minerals added for flavor and pH balance) for potable use, and waste hygiene and urine water for electrolysis, with in situ quality monitoring of conductivity only (everything else returned to earth for sampling). The US and Russian water supplies could not be mixed because the different biocides used would yield a solid precipitate and clog lines. The design constraints called for design loads are listed in Table 2 (Wieland 1994).
Fig. 7

Water Recovery System for the International Space Station (NASA 2000)

Table 2

Design loads per person per day (Wieland 1994)

Parameter

US standard

Russian standard

Crew-generated moisture

1.82 kg (4.01 lb)

N/A

Water consumption

2.8 kg (6.2 lb)

2.5 kg (5.5 lb)

Hygiene water usage

6.8 kg (15.0 lb)

4.53 kg (9.96 lb)

Urine production

1.56 kg (3.43 lb)

1.2 kg (2.64 lb)

Biocide

Iodine (I2)

Silver (Ag)

Shower water usage

One 5.5 L (1.5 gal) every 2 days

One 10 L (2.6 gal) every week

Life science experiments

3.34 kg (7.35 lb)

3.34 kg (7.35 lb)

Since 2008, the onboard WRS has supplied the potable and hygiene water needed by the ISS crew and has also reclaimed and processed atmospheric condensate and wastewater, through a system of recycling, distillation, and filtration (Fig. 8). The WRS, which was initially installed in the ISS Destiny Module November 2008 and later moved to the Tranquility (Node 3) Module in February 2010, resides on two of the three Environmental Control and Life Support System racks, where it ensures availability of potable water for crew drinking and hygiene, oxygen generation, urinal flush water, and payloads. Inputs are urine, humidity condensate, and Sabatier product water. Output is potable water, which is supplied to the potable bus or stored in water bags for future use when the potable bus needs supplementing. The advent of the WRS reduced the need for water resupply from earth by 6,800 kg (15,000 lb) per year and allowed a doubling of the ISS occupancy to six people. Although rare and temporary, ISS occupancies greater than six people have been supported by the WRS, for example, when the 2013 Sochi Olympics torch was relayed to ISS and increased occupancy to nine crew members (Howell 2013). Altogether, the WRS is comprised of four components: the Urine Processor Assembly, the Waste and Hygiene Compartment, the Water Processor Assembly, and the Elektron System (Wieland 1998; McCoy 2012; Pruitt et al. 2015; Carter 2014; NASA Facts 2008).
Fig. 8

ISS WRS (NASA 2008)

The ISS Urine Processor Assembly (Fig. 9), a $$250 million system that recycles sweat and urine into potable water, uses distillation, filtration, ionization, and oxidation to produce approximately 2,700 L (713 gal) of potable water per year for the ISS. This onboard water production enables the reduction of ground launched water by approximately 65%. The Urine Processor Assembly uses a low-pressure vacuum distillation process and a rotating centrifuge to effectively separate liquids and gases from urine inflow in microgravity (Pruitt et al. 2015; Carter 2014). Wastewater from the Waste and Hygiene Compartment, a storage tank for wastewater, is sent to the Urine Processor Assembly recovery (Fig. 10). The Russian segment has its own similar storage compartment for wastewater (Pruitt et al. 2015; Carter 2014). The Urine Processor Assembly was designed to handle a load of 9 kg (19.8 lb) per day and recover 85% of the water content, which supports the needs of a 6-person crew (Carter 2009; Carter 2014). However, this percentage water recovery was later revised to 70%, due to calcium sulfite precipitation from increased urine calcium levels, which originates from bone loss in microgravity. After distillation, the outflow is combined with other wastewater streams and enters the Water Processor Assembly for treatment (Pruitt et al. 2015).
Fig. 9

Installation of the ISS Urine Processor Assembly by Jeffrey Williams (NASA 2010)

Fig. 10

ISS Urine Processor Assembly schematic (Wieland 1998)

Outflow from the Urine Processor Assembly and other wastewater sources are combined to feed the Water Processor Assembly (Fig. 10). The Water Processor Assembly intakes processed water from Urine Processor Assembly, recovered condensate from Air Contamination Control system, and other system wastewater. First, the Water Processor Assembly filters out free gases and solids (e.g., hair) from inflow wastewater, then passes this water through multifiltration beds. Next, microorganisms, organic material, and other contaminants are removed by high-temperature catalysis. The resulting water is then tested by electrical conductivity sensors to ensure the highest drinking water standards. Unacceptable water is cycled back into the water processor assembly for retreatment. To ensure system reliability and ability to provide for increased crew sizes, water quality is tested regularly. As an alternative to drinking water, reclaimed water from the Water Processor Assembly may also be used to generate oxygen for breathing by feeding the Elektron Oxygen Generating System, which uses electrolysis to split liquid water into oxygen and waste hydrogen (Pruitt 2015; Carter 2014).

Overall, the WRS has had limited downtime and is a reliable, efficient system. Initially, there were stigmas associated with reclaimed water use and urine recycling, but they were overcome through open communication, taste tests, and other forums to encourage acceptance among stakeholders. The ISS obtains approximately 75% of its potable water from the WRS and is able to store excess water for contingencies. On a daily basis, the system processes 7 L (1.8 gal) of condensate and 7 L (1.8 gal) of urine, while reclaiming/producing 12 L (3.2 gal) of potable water. This progression from ground supplied water to onboard recycling has reduced costs and allowed for long-duration missions. The success of this WRS underscores the value of proper planning, the need for continued monitoring, and the challenges and strengths of multidisciplinary collaboration (McCoy 2012).

Aboard the ISS, water and interior surface samples are analyzed in flight and on the ground for bacteria that may be harmful to the crew. Thus far, bacteria encountered on the ISS have represented common strains at low levels below the 10,000 colony forming units per 10 cm2 threshold that may cause illness. Microbial growth has only been observed during periods of stagnancy and no pathogenic organisms have been detected (McCoy 2012). Similarly, microbial examination of drinking water at various stages has shown that iodine and silver biocide treatment has successfully removed pathogenic microbes. The ISS onboard systems consistently produce potable water of acceptable quality, with only a few instances of contaminant levels elevated above acceptable quality limits of the spacecraft water exposure guidelines (Table 3). These were caused by increased silver, added to ground-supplied water, to inhibit microbial growth and increased total organic carbon from benign compounds (Limero and Wallace 2017).
Table 3

Spacecraft Water Exposure Guidelines for potable water (NASA 2017; Barta 2017)

Chemical

Concentration (mg/L)

1 day

10 days

100 days

1000 days

Acetone

3500

3500

150

15

Alkylamines

0.3

0.3

0.3

0.3

Ammonia

5

1

1

1

Antimony (salts)

4

4

4

4

Barium (salts)

21

21

10

10

Benzene

21

2

0.07

0.07

Cadmium (salts)

1.6

0.7

0.6

0.022

Caprolactam

200

100

100

100

Chloroform

60

60

18

6.5

Dibutyl phthalate

1200

175

80

40

Dichloromethane

40

40

40

15

Ethylene glycol

270

140

20

4

Formaldehyde

20

20

12

12

Formate

10,000

2500

2500

2500

Manganese (salts)

14

5.4

1.8

0.3

Mercaptobenzothiazole

200

30

30

30

Methanol

40

40

40

40

Methyl ethyl ketone

540

54

54

54

Nickel

1.7

1.7

1.7

0.3

Phenol

80

8

4

4

Silver

5

5

0.6

0.4

Zinc

11

11

2

2

ISS water quality is measured by taking both real-time and archival samples for analysis on Earth. Archival samples are collected in Teflon bags and returned to Earth to the Toxicology and Environmental Chemistry Laboratory at NASA Johnson Space Center in Houston, Texas. There, the samples undergo gas chromatography, mass spectrometry, ion chromatography, liquid chromatography, and leuco crystal violet for further analysis (Table 4). The considerations for existing water quality monitoring systems include protection of crew, the individual strengths and susceptibilities of astronauts, spaceflight relevant chemicals, and exposure durations critical for spaceflight (Barta 2017). Currently, multiple low cost, multiuse sensors are being developed for future exploration missions for as-needed analyses (Limero and Wallace 2017).
Table 4

Analytical methods for analysis of archival water samples (Limero and Wallace 2017)

Parameter

Method

Standard

pH

Potentiometric

SM 4500H

Conductivity

Potentiometric

SM 2510B mod

Turbidity

Nephelometric

SM 2130B mod

Total solids

Gravimetric

SM 2540B mod

Total organic carbon

UV or heated persulfate oxidation

EPA 415.1 mod/SM 5310C mod

Iodine

LCV

Custom

Anions and cations

IC

EPA 300.0 mod

Trace metals and minerals

ICP/MS

SM 3125B mod

Volatile organics

Purge-and-trap GC/MS

EPA 524.2 mod

Semivolatile organics

GC/MS

EPA 625 mod

Nonvolatile organics

LC with UV detection

Custom

Alcohols and glycols

Direct-injection GC/MS

Custom

Silanols

LC with refractive index detection

Custom

Carboxylates

IC

Custom

Amines

IC

Custom

Aldehydes

GC/MS

Custom

GC/MS, gas chromatography/mass spectrometry; IC, ion chromatography; ICP/MS, inductively-coupled plasma mass spectrometry; LC, liquid chromatography; LCV, Leuco crystal violet; UV, ultraviolet.

Future Missions

For short missions, monitoring water quality through archival methods is sufficient, if pre- and postflight samples are shown to be contaminant free. But for long-duration missions beyond low Earth orbit, in which potable water is produced from processed wastewater, real-time measurements must be made for total organic carbon, total inorganic carbon, pH, and conductivity, of both potable water and wastewater, as well as medical, science, and planetary origin water (Barta 2017). It will also be necessary to conduct in-flight identification and quantification of microbial groups or species. Furthermore, water stored in large tanks for longer missions (e.g., NASA’s Orion missions) must be tested and treated to discourage microbial growth and chemical leaching (Limero and Wallace 2017).

To address this insufficiency in water quality monitoring for long-duration missions beyond low Earth orbit, NASA is developing a compact in-flight water quality monitoring laboratory to measure various water quality properties. The components of this suite include: (1) a commercial off the shelf unit, called RAZOR EX, with customized sample pouches developed for microbial monitoring of target microorganisms in less than 1 hour using polymerase chain reaction (PCR); (2) a commercial off the shelf colorimeter unit, called HACH, with customized sample kit for reactive silica monitoring; and (3) a technique for organic monitoring, called Organic Water Module. This set of hardware will ensure that crew members can test and monitor the quality of their water supply for long-duration missions, where reliability, long working life (more than 3 years), stable calibration, and operating ability in micro- or partial-gravity are required (Khodadad and MacAskill 2017).

Long-duration mission systems must also account for higher drinking water consumption rates. These should drive design goals for water recycling, but not be so stringent as to cause over design. It is estimated that two water recycling and storage subsystems will be required for long-duration space missions beyond low Earth orbit: one to process concentrated feeds, like urine and flush water, and another to process dilute feeds, like laundry and shower water. Potable water would be recovered through distillation and filtration, while lower quality water would be recovered by filtration alone. Wastewater should also be recoverable. This includes hygiene, laundry, and dish water, water recovered from solid wastes, and biological life support (nutrient solution). For deep space missions, research is being conducted on using stored water as a radiation shield; however, water recovery will be important for replenishing this resource. For extraterrestrial missions, obtaining water from planetary sources, asteroids, and comets is being studied (Barta 2017).

Water management is also important to prevent contamination of Earth and other solar system objects. Spacecraft and their components, including water systems, must be cleaned, particularly if used for life detection experiments, or where indigenous life may be present and susceptible to invasive species proliferation. For example, bio-monitoring tests of spacesuits (e.g., LOCAD-PTS) before exposure to other planets, like Mars, can be used to minimize human contamination of the martian surface, minimize complication of the search for extraterrestrial life, and maintain compliance with the Outer Space Treaty, which has been ratified by over 100 countries and seeks to avoid harmful contamination of space. Ultimately, improving the existing regenerative methods for water management, recovery, and quality monitoring will be essential for long-duration space missions beyond low Earth orbit, where the volume and mass of consumables required and waste generated for a mission of months or years may be prohibitively expensive to launch to space and return to Earth (NASA Facts 2008).

Cross-References

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Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  1. 1.University of PennsylvaniaPhiladelphiaUSA

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