To ensure our survival, the earth provides human beings and animals with an atmosphere that contains necessary gases such as oxygen, a plethora source of water as well as a rich ores and fauna that provides a constant source of nourishment.
While our survival is protected by the atmosphere of the earth, once you leave this planet and head into space these perfected environmental conditions disappear. For short space missions, this challenge has been previously solved by astronauts taking everything required for survival on the space shuttle with them.
Longer space missions are a challenge for astronauts as these sources can be reduced to very little. Of these supplies include the transportation of water, as this takes up a large amount of space on the spacecraft. For example, it is estimated that to send just one kilogram of supplies to the ISS costs around $25,000 USD1.
Although the astronauts try to save as much water as possible on missions, it is estimated that each astronaut will require at least 30 liters of water every day2. This is particularly low, as it is estimated that an average person on Earth consumes approximately 160 liters of drinking water each day3.
For a six-month stay on the ISS, a daily consumption of 30 liters of water and its transportation on the shuttle costs around $135 million USD, however this large amount of money could be significantly reduced if an effective recycling system was put into place.
ESA astronaut Tim Peake working on the water processor assembly on board the ISS in 2016. Photo: NASA / flickr.com/photos/nasa2explore
Recycling to Improve Survival in Space
The Environmental Control and Life Support System (ECLSS) ensures that all astronauts experience hospitable conditions when on space missions. For example, the ECLSS controls the temperature and humidity in the cabin. In 2006 and 2008, in an effort to improve independence of space shuttles from deliveries from Earth, the ECLSS implemented an oxygen generation system and water recovery system for space shuttles.
Water makes up approximately 92% of the total mass of consumables that astronauts need to survive in space4. Discovering a way to dramatically reduce the need for water deliveries for astronauts from Earth would therefore decrease the total demand for supplies to a large scale while also saving an incredible amount of money for space agencies. Additionally, by implementing water recovery systems in space, future missions where deliveries to space shuttles, such as manned trips to Mars, may become a real possibility.
Figure 1. Top: The ISS crew drinking water from the new recycling system for the first time. Middle: Foods that contain lots of water, such as the creamed spinach in the image, are taken in dehydrated form. They are rehydrated in space using recycled water. Photos: NASA / spaceflight.nasa.gov. Bottom: Astronaut Peggy Whitson with a rehydrated space cheeseburger. Photo: NASA / flickr.com/photos/nasa2explore.
Creating Drinking Water from Urine and Sweat
The water recovery system (WRS) installed on the ISS achieves a recovery rate of approximately 93%, however the origin of this water can be from urine, ambient air, moisture from the astronaut crew’s sweat and breath, as well as even from their laboratory animals.
The WRS is comprised of two main parts: the water processor assembly and the urine processor assembly. To recover water from urine, the urine is first distilled in the urine processor assembly, which requires a uniquely developed installation to ensure that liquid and gas are separated from each other in the absence of gravity.
The recovered water is then mixed with the rest of the wastewater that is cumulatively treated in the water processor assembly. Once the free gases and solids, such as hair, have been removed, the water is treated in a series of titers and chemical processes. Following this initial processing, any remaining organic contaminants and microorganisms are removed in a high-temperature catalytic reaction. Conductivity measurements are then performed to determine whether the water is clean enough to be reused, and if not, further decontamination of the water will be conducted.
Figure 2. The Environmental Control and Life Support System (ECLSS) used on the ISS ensures hospitable conditions on board, for example by controlling the temperature and humidity and supplying clean water.
The Development of the WRS
The water recovery system on the ISS was originally developed by a joint effort between NASA's Marshall Space Flight Center in Huntsville, Alabama, and the Hamilton Sundstrand Space Systems International, which is now known as the UTC Aerospace Systems. The UTC Aerospace Systems also produces the spacesuits and life support systems that are currently used by the ISS crew uses on spacewalks.
To adapt a water recovery system that is perfectly aligned to the sewage and wastewater that it must process in space, which is primarily composed of urine and ambient air condensate, it has to be tested on the corresponding material during the development phase. To do this, the developers create synthetic substitute solutions, which have as similar a composition as possible to the urine or the ambient air condensate found on the ISS.
Substitute Solutions as Test Samples
In 2004, Verostko et al5. developed standard formulations for various substitute solutions, some of which included urine substitute solutions and solutions that simulate the waste water on a space flight or on a potential base on another planet. Verostko’s team conducted ion chromatography measurements to determine the chemical composition of the liquid to be processed.
Based on the knowledge gathered from these analyses, the team of researchers established the substitute solutions and then utilized ion chromatography to monitor the concentrations of inorganic anions and cations present within the solutions.
Figure 3. Astronaut Tim Kopra carrying out routine maintenance on the urine processor assembly. Photo: flickr.com/photos/ nasa2explore.
Taking Recycling into Deep Space
The single use of life-sustaining materials, such as water and oxygen, is not feasible for long-term space missions, as the transport of these materials is often expensive. For future manned space missions that will be traveling further distances from the earth, such as NASA’s 2030 plans for missions to Mars, providing a constant supply will not be practical.
The astronauts will therefore be reliant on a more efficient recycling system. Until missions to Mars and other planets become a reality, further research will be required to advance future life sustaining technologies that will allow for the survival of all astronauts on their round-trip journey from these locations in space. A new water recovery system that aims to recover up to 98% of water is already in development and is expected to be unveiled this year.
Figure 4. Astronaut Samantha Cristoforetti enjoying a cup of espresso on the ISS – made from recycled water of course. Photo: NASA / twitter.com/AstroSamantha.
- http://www.businessinsider.com/spacex-rocket-cargo-price-by-weight-2016-6 http://cs.astrium.eads.net/logbook/Logbuch/2/beitrag1.html
- https://www.energie-umwelt.ch/haus/badezimmer/wc- spuelung
- Tamponnet, C.; Savage, C. J.; Amblard, P.; Lasserre, J. C.; Personne, J. C.; Germain, J. C. Water Recovery in Space; ESA bulletin 97: March 1999
- Verostko, C. E.; Carrier, C.; Finger, B. W. Ersatz wastewater formulations for testing water recovery systems. SAE Technical Paper 2004-01-2448, 2004, doi:10.4271/2004-01-2448.
This information has been sourced, reviewed and adapted from materials provided by Metrohm AG.
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