Sustaining Life -- Where Would a Space Explorer Find Water and Oxygen?
Food. Water. Air. Shelter. All living things have these basic needs.
On Earth, people know where to find them. In space, these items usually have to be carried from Earth. While in space, an astronaut usually needs 30.60 kilograms (67.32 pounds) of food, water and air per day to be healthy. Imagine that a crew of three astronauts for a one-year mission would need 33,000 kg (70,000 lb) of food, water and air. It would be impossible to carry that many supplies from Earth. Recycling is one solution to this problem.
Image above: Astronauts may choose from a variety of foods. Credit: NASA.
Cleaning and recycling the air is a big concern for NASA scientists as they plan for longer trips in space. In space and on Earth, human beings breathe out carbon dioxide, or CO2. Too much carbon dioxide, especially in a small, enclosed space, can be poisonous. Air inside the spacecraft must be "cleaned" to remove excess carbon dioxide. Some of the excess carbon dioxide is released into outer space. Oxygen may be removed and used from some of the carbon dioxide. Back-up systems are in place to ensure that excess carbon dioxide isn't trapped in an astronaut's living space.
Other gases trapped in the spacecraft can also be dangerous. The gases may come from chemicals, leaks and outgassing from materials. Outgassing happens when gases trapped inside materials slowly leak out of those materials and into the air. Stuffed animals, DVD labels and some electronics cannot be carried into space because they have outgassing issues. The trace contaminant control system removes these trace odors and gases because they could accumulate and harm a crew.
Currently, each astronaut aboard the International Space Station, also known as the ISS, uses about three gallons of water daily. The average American on Earth uses about 35 gallons of water per day.
An astronaut on an extended stay on the ISS could use up to 10.6 tons of water per year. A crew of four on a three-year trip to Mars is expected to use 127.5 tons of water. That much water is too heavy to carry on a spacecraft.
Water will have to be recycled in space. One method of recycling water uses catalytic oxidation, a process that kills bacteria and viruses. Unwanted materials are removed from the water, and the water is cleaned. It will be necessary to collect water from bathing, washing, sweating, urine and the air's humidity. Through this process, NASA can make the collected water even cleaner than water that flows from a faucet on Earth.
Currently, all food that astronauts need during their mission is carried into space -- 1.83 kg (slightly more than four pounds) of food and packaging is carried on the ISS for each astronaut. Of this amount, 1.56 kg (a little less than 3.5 lb) is food; the rest is packaging. Based upon these amounts, a 1000-day mission to Mars would require 1830 kg (4,035 lb) -- more than two tons of food and packaging for each astronaut! Carrying this much food would be nearly impossible.
To avoid carrying such large amounts of food, scientists are working on ways to grow or "create" that food. Plants may be a food source. They may also help recycle carbon dioxide into oxygen.
Food. Water. Air. Shelter. Human beings' basic needs will not change whether they live on Earth or travel to Mars. What will change is how they meet these needs. NASA researchers, scientists and engineers are working to find new ways to supply all that people will need for long-duration space flights.
Jitendra Joshi, Michele Perchonok and Debbie Berdich/SME