In August of this year, the ISS detected a slight drop in cabin air pressure. Cosmonauts later discovered a 2 mm hole in the cabin of the Russian Federation's MS-09 manned spacecraft. The leak has now been successfully repaired. Roscosmos president Rogozin said the investigation found that the leak was caused by a mistake made by ground workers during the manufacturing process. If not repaired, the ISS's oxygen would have leaked completely within 18 days, with unimaginable consequences.
The ISS has long been staffed by three astronauts (six during shifts) and has conducted various experiments and space missions. Therefore, it is very important to have a good life support system. The first thing to address in this system is the oxygen supply.
So where does the oxygen used by ISS astronauts come from? Some readers may think that the oxygen in the ISS is transported from Earth on spacecraft, but this is not accurate. The ISS is equipped with an oxygen generation system. It works by ionizing water to produce oxygen, which is then released to the station, where hydrogen can be reused. This equipment is so efficient at producing oxygen that it is the primary source of oxygen for ISS astronauts. The system can produce 12 pounds of oxygen per day, which can be used by 10 people and is enough for three astronauts on a long-term station.
In addition, the system can increase the amount of oxygen produced in an emergency by up to 20 pounds per day. Meanwhile, the ISS is equipped with an efficient air filtration system. After the exhaled carbon dioxide is separated, the carbon dioxide reacts with hydrogen to form water and methane. Methane is vented directly and water is used in the water cycle or electrolyzed to produce oxygen. Exhaust gases including ammonia, hydrogen sulfide and instrumentation work will be completely filtered out.
This oxygen generation system is still being improved. In addition, compressed air, oxygen and water will be added to the ISS to ensure the needs of the astronauts.