When humans travel away from Earth, they need to take supplies. On the International Space Station, new supplies are periodically sent. The new supplies usually consist of food, clothes, experiments and equipment for experiments. Sending supplies to the space station can be costly.
Earth's natural life support system provides the air we breathe, the water we drink and other conditions that support life. But a life support system has to be created for a spacecraft, especially for trips far from Earth. If humans build outposts on the moon or travel to Mars or an asteroid, they must take what they need and recycle what they use.
On the space station, the Environmental Control and Life Support System, or ECLSS, helps to keep the crew healthy by:
Providing water for drinking, food preparation and hygiene
Removing carbon dioxide from the air
Filtering the air
Maintaining the air pressure
Maintaining temperature and humidity levels
Distributing air between connected space station modules
ECLSS has two main components: The Water Recovery System, or WRS, and the Atmosphere Recovery System, or ARS. The WRS recycles the crew’s sweat, urine and other wastewater and purifies it to make it potable, or drinkable. The ARS keeps the air in the cabin clean of contaminants like carbon dioxide. One part of the ARS is the Oxygen Generation System. It uses some of the station’s water to provide oxygen. The space station crew can include lab animals, like rodents, that breathe and urinate, too. Vapors from these "crew mates" are recycled with the waste and vapors from the human crew. About 72 rats would equal one human in terms of water that is collected.
Recycling Like Mother Nature Earth is like a giant spacecraft. It travels through space orbiting the sun once a year. The crew aboard spaceship Earth consists of all of the people on the planet. All of the supplies are on our planet. Everything we need is already here for us to use and reuse.
Earth recycles water and air for its crew. There is no new water on our planet. The rain that falls from the sky was once on Earth. Mother Nature's water cycle has allowed Earth's inhabitants (people, plants and animals) to use and reuse the same water that has been here since the beginning. A city's water treatment plant recycles the water we use in our homes, schools and businesses.
On the station, ECLSS has a two-part water recovery system. The Urine Processor Assembly, or UPA, removes water from the urine of the crew. Then, the Water Processor Assembly cleans the water from the UPA and the water that comes from the crew's sneezing, breathing, sweating and washing. The Water Recovery System uses simple Earth-based technologies to recycle the water, but making those technologies work in an environment that has almost no gravity makes it complicated, because the water will not move unless you push it and the gas will not separate from the water. You could say that the water starts off cleaner because space station water does not have waste from pesticides and other chemicals that water on Earth has. Station water has low levels of bacteria. Water that you drink at home -- and bottled water -- likely has more bacteria, but not the kind that make you sick. A sensor on ECLSS checks the water purity. If the water is not pure enough, it goes through the cycle again. Water that passes the purity test is stored for later use. More than 90% of water on station is reused. And the crew is careful not to waste the water. While a person in the U.S. uses about 35 gallons of water per day, a person on the station uses a mere three gallons daily. Three gallons sounds like a small amount but is not as bad as it sounds, since the station has no shower, dishwashers, sinks, Earth-like toilets or washing machines that can use many gallons of water a day.
Watch Mike Fincke explain how astronauts use the bathroom and shower in space.
On Earth, plants help to recycle air. When humans exhale, we release carbon dioxide, or CO2. Plants use the carbon dioxide during photosynthesis and then release oxygen. On the space station, ECLSS has a carbon dioxide removal assembly, or CDRA, that pulls the carbon dioxide out of the space station cabins. But ECLSS creates oxygen from water by a process called electrolysis. ECLSS uses an electrical current to break many molecules of H2O (two hydrogen atoms and one oxygen atom) into hydrogen gas (H2) and oxygen gas (O2). The oxygen is released for the crew to breathe.
Recycling in Space Helps Earth Besides recycling in space, NASA recycles on Earth. All NASA centers recycle paper, plastic and batteries. Some NASA centers recycle leftover materials from construction and demolition projects.
As we learn to live away from Earth, in confined spaces where contaminating the environment can be felt quickly by the crew and can make them sick, we learn to do more with fewer resources. We learn, by necessity, to be smart when designing food and supply containers because they will generate trash that will have to be stored or recycled in the same cabin where we are living. We also learn to conserve our resources, like water, because we do not have a huge supply of them or have fast access to them.
What NASA has learned about recycling in space helps Earth in other ways. When companies use what NASA has learned to make new products, those products are called spinoffs. Water and air filters have been created for Earth based on NASA space station and space shuttle recycling technology. And parts of NASA's water purifying systems have been used to help villages that do not have clean water provide it for their citizens.
NASA saves thousands of dollars by recycling. Purifying water on the station means about 15,000 pounds of water per year do not have to be sent to space. This is more than the weight of sending ECLSS to the station with replacement parts. And it saves about $2 billion -- enough to buy a fast food meal for every person in the United States. That savings will be especially important when NASA sends crews farther away from Earth. It would take many months to send supplies to a crew on Mars, and it would cost billions of dollars. Recycling today is helping NASA plan for the future of exploration.
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