The International Space Station, or the ISS, plays a crucial role in providing a comfortable living space for its inhabitants. But how do astronauts stay alive in space? How does the spacecraft manage to get all of the oxygen it needs without spending too much money? The answer is through a Water Reclamation System (WRS) and an Oxygen Generation System.
The issue of breathing in space is a huge concern. A constant supply of air is needed, and breathable air requires a specific mixture of nitrogen, oxygen, argon, carbon dioxide and other gases that must be reproduced as best possible.
The WRS helps to reclaim the water that has been brought onto the ISS – for example, through the humidity condensation on the walls and windows on the ship, extra vehicular waste and the astronauts’ urine. All of the liquid that is gathered is then purified and reused. The purification process is held to extremely high standards so that it maintains the quality that is needed to be considered clean water. Although this amount cannot completely fuel the ISS, it does help reduce the amount that is needed from Earth.
The connection between the WRS and the Oxygen Generation System is the transition between the liquid state of oxygen in water and the gas state of oxygen. The Oxygen Generation System comes into play by causing electrolysis to split the water apart into its hydrogen and oxygen molecules. In order to do this, an electric current is sent through the ISS solar panels and through the water to form the positive anode and the negative cathode. These, in turn, are what actually separate the atoms and recombine them into their gas forms of hydrogen and oxygen.
The best comparison to this process is photosynthesis. When plants absorb water, they also break it down to create hydrogen and oxygen. The hydrogen is then combined with carbon dioxide. This helps the plants to create food in the form of carbohydrates and then the oxygen, which is not needed for the plant to function, is expelled.
The hydrogen generated from electrolysis on the ISS is actually fed back into the space station through what’s known as the Sabatier System. There is a catalyst used to combine both the waste hydrogen and the waste carbon dioxide, which is obtained from the astronauts’ exhalations, and then these are combined to create water and methane. The water is able to be transferred back into the WRS and the methane is vented into space. This is a very efficient way of keeping astronauts alive, as shipping all of the oxygen from Earth would be very costly. Because of this system, everyone aboard the ISS can relax and breathe with ease.