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Thumbnail of How does the space station never run out of oxygen? - Alvaro Romero-Calvo and Theo St Francis

How does the space station never run out of oxygen? - Alvaro Romero-Calvo and Theo St Francis

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  1. 0:07 You’re an astronaut orbiting 400 kilometers above Earth when suddenly an alert flashes across your display.
  2. 0:15 The system responsible for producing the breathable air on board has failed.
  3. 0:21 Now, you and your crewmates must work with mission control to identify the problem and fix it as quickly as possible.
  4. 0:30 This might seem like a scene from a sci-fi thriller, but for astronauts on the International Space Station, dealing with situations like this is a reality of life.
  5. 0:40 For over 25 years, ISS’s air supply systems have revolutionized space missions.
  6. 0:47 Yet the need for regular maintenance, repairs, and upgrades has pushed engineers to develop even more reliable systems for future spacecraft.
  7. 1:01 Creating breathable air in space has two requirements: supplying oxygen and removing exhaled carbon dioxide before it builds up.
  8. 1:12 Every astronaut in space needs, on average, about 0.8 kilograms of oxygen a day.
  9. 1:19 Most early space missions met this demand by storing oxygen on board in pressurized tanks.
  10. 1:26 For example, the eight-day Apollo 11 mission to the moon carried three astronauts, along with around 50 kilograms of oxygen for life support
  11. 1:37 more than enough for the crew to survive on.
  12. 1:41 Canisters containing lithium hydroxide would chemically react with carbon dioxide, scrubbing it from the cabin.
  13. 1:49 But the launch of the first space station marked a turning point.
  14. 1:53 For the first time, crews would remain in orbit for months, not days.
  15. 1:59 A typical 6 to 8 month expedition with seven crew members might require over a thousand kilograms of oxygen, demanding about 30 large tanks.
  16. 2:10 And constantly shipping this massive load to and from orbit would be expensive.
  17. 2:16 So, engineers developed a solution: using water and a process called electrolysis, a system that makes oxygen directly onboard.
  18. 2:26 Water is relatively easy to come by on the ISS thanks to its robust recovery system.
  19. 2:33 It captures nearly all moisture onboard - from sweat, exhalation, wash water, and even urine
  20. 2:43 and purifies it into fresh, potable water.
  21. 2:46 This clean water is routed to an electrolyzer, a device equipped with two electrodes, one positive and one negative.
  22. 2:55 When an electric current is applied, the electrolyzer breaks down water molecules into oxygen and hydrogen gases.
  23. 3:04 Oxygen collects near the positive electrode, and hydrogen gas bubbles form near the negative electrode.
  24. 3:11 But there’s a problem - getting these gases out of the water.
  25. 3:16 On Earth, bubbles naturally float to the top of denser liquids due to gravity.
  26. 3:22 But in orbit, where everything is in freefall, bubbles tend to cling to the electrodes.
  27. 3:28 One solution is to pump water through the electrolyzer, carrying the bubbles away to a separator.
  28. 3:36 Here, the gas-filled water is spun much like a washing machine in its final spin cycle, forcing the liquid outward while the gas collects in the center.
  29. 3:46 In the end, oxygen is released into the cabin.
  30. 3:50 Hydrogen gas is either vented into space or routed to a reactor, where it combines with captured exhaled carbon dioxide to make methane and water.
  31. 4:02 But this system isn't perfect.
  32. 4:04 The process for separating bubbles from water relies on many complex moving parts that are prone to breaking or malfunctioning.
  33. 4:13 And as space agencies set their sights on expeditions deeper into space, like year-long crewed trips to Mars, this approach becomes increasingly impractical.
  34. 4:25 So, researchers are exploring new ways to separate out this gas.
  35. 4:30 One promising solution is to spin the gas-filled water inside the electrolyzer using magnets.
  36. 4:38 This system takes advantage of a fundamental property of how electrons and magnets interact.
  37. 4:45 When negatively charged molecules move perpendicularly through a magnetic field, the field applies a force on the molecules called a Lorentz force.
  38. 4:55 It pushes them sideways, at a right angle to both the electric and magnetic fields.
  39. 5:02 So, by positioning the magnets and current path in just the right way, this Lorentz force can swirl the liquid,
  40. 5:11 separating out the oxygen and hydrogen gases - no pump or separator needed.
  41. 5:18 This Magnetohydrodynamic Oxygen Generation Assembly, or MOGA, has no moving parts, so it requires less maintenance and replacement hardware,
  42. 5:30 freeing up space onboard and allowing astronauts to spend more time on other endeavors.
  43. 5:36 MOGA is still in the research phase, but it holds promise.
  44. 5:41 With a more robust oxygen system, astronauts on future space stations and deep-space missions should be able to breathe a little easier.

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