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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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คำบรรยาย (87)
0:06
You’re an astronaut orbiting 400 kilometers above Earth
0:11
when suddenly an alert flashes across your display.
0:15
The system responsible for producing the breathable air on board has failed.
0:20
Now, you and your crewmates must work with mission control
0:24
to identify the problem and fix it as quickly as possible.
0:29
This might seem like a scene from a sci-fi thriller,
0:32
but for astronauts on the International Space Station,
0:36
dealing with situations like this is a reality of life.
0:40
For over 25 years,
0:42
ISS’s air supply systems have revolutionized space missions.
0:47
Yet the need for regular maintenance, repairs, and upgrades
0:51
has pushed engineers to develop even more reliable systems for future spacecraft.
1:01
Creating breathable air in space has two requirements:
1:05
supplying oxygen and removing exhaled carbon dioxide before it builds up.
1:11
Every astronaut in space needs, on average,
1:14
about 0.8 kilograms of oxygen a day.
1:18
Most early space missions met this demand
1:21
by storing oxygen on board in pressurized tanks.
1:25
For example, the eight-day Apollo 11 mission to the moon
1:30
carried three astronauts,
1:32
along with around 50 kilograms of oxygen for life support—
1:36
more than enough for the crew to survive on.
1:40
Canisters containing lithium hydroxide
1:43
would chemically react with carbon dioxide,
1:46
scrubbing it from the cabin.
1:48
But the launch of the first space station marked a turning point.
1:52
For the first time, crews would remain in orbit for months, not days.
1:58
A typical 6 to 8 month expedition
2:01
with seven crew members might require over a thousand kilograms of oxygen,
2:06
demanding about 30 large tanks.
2:09
And constantly shipping this massive load to and from orbit would be expensive.
2:15
So, engineers developed a solution:
2:18
using water and a process called electrolysis,
2:21
a system that makes oxygen directly onboard.
2:26
Water is relatively easy to come by on the ISS
2:30
thanks to its robust recovery system.
2:32
It captures nearly all moisture onboard—
2:36
from sweat, exhalation, wash water, and even urine—
2:42
and purifies it into fresh, potable water.
2:46
This clean water is routed to an electrolyzer,
2:49
a device equipped with two electrodes, one positive and one negative.
2:55
When an electric current is applied,
2:57
the electrolyzer breaks down water molecules into oxygen and hydrogen gases.
3:03
Oxygen collects near the positive electrode,
3:06
and hydrogen gas bubbles form near the negative electrode.
3:11
But there’s a problem— getting these gases out of the water.
3:15
On Earth, bubbles naturally float to the top of denser liquids due to gravity.
3:21
But in orbit, where everything is in freefall,
3:24
bubbles tend to cling to the electrodes.
3:28
One solution is to pump water through the electrolyzer,
3:32
carrying the bubbles away to a separator.
3:35
Here, the gas-filled water is spun much like a washing machine
3:39
in its final spin cycle,
3:41
forcing the liquid outward while the gas collects in the center.
3:46
In the end, oxygen is released into the cabin.
3:50
Hydrogen gas is either vented into space or routed to a reactor,
3:55
where it combines with captured exhaled carbon dioxide
3:59
to make methane and water.
4:01
But this system isn't perfect.
4:04
The process for separating bubbles from water
4:07
relies on many complex moving parts that are prone to breaking or malfunctioning.
4:12
And as space agencies set their sights on expeditions deeper into space,
4:17
like year-long crewed trips to Mars,
4:21
this approach becomes increasingly impractical.
4:25
So, researchers are exploring new ways to separate out this gas.
4:30
One promising solution
4:32
is to spin the gas-filled water inside the electrolyzer using magnets.
4:37
This system takes advantage of a fundamental property
4:41
of how electrons and magnets interact.
4:44
When negatively charged molecules move perpendicularly
4:48
through a magnetic field,
4:50
the field applies a force on the molecules called a Lorentz force.
4:55
It pushes them sideways,
4:57
at a right angle to both the electric and magnetic fields.
5:02
So, by positioning the magnets and current path in just the right way,
5:08
this Lorentz force can swirl the liquid,
5:11
separating out the oxygen and hydrogen gases—
5:15
no pump or separator needed.
5:18
This Magnetohydrodynamic Oxygen Generation Assembly, or MOGA,
5:24
has no moving parts,
5:26
so it requires less maintenance and replacement hardware,
5:29
freeing up space onboard
5:31
and allowing astronauts to spend more time on other endeavors.
5:36
MOGA is still in the research phase, but it holds promise.
5:41
With a more robust oxygen system,
5:43
astronauts on future space stations and deep-space missions
5:47
should be able to breathe a little easier.
