They say that the best things in life are free. While some may not agree with
this timeless adage, we can all agree that it’s true for at least ONE THING,
something that most living creatures cannot survive without—oxygen!
As a species, humans not only live on Earth, but also in space! No Martian colonies yet,
but we do have humans living long-term around our planet.
Now, we all know that we have plenty of breathable oxygen on Earth,
but ensuring ready access to sufficient amounts of breathable oxygen IN SPACE is
one of the most crucial tasks of space scientists and engineers. So how do
they do it? How do astronauts get access to a reliable source of breathable oxygen in space?
Firstly, it’s important to note that although humans send many
manned satellite missions to space, each one differs in their mission objectives,
tasks and duration. Since many routine space missions are usually designed to
last only a few days, up to a week or two, most spacecraft carry their own supply of
oxygen onboard the spacecraft. They may also have a backup system for emergencies.
However, what if the duration of a particular space mission is longer? For example, consider
the International Space Station, or the ISS. It is the largest and most expensive manned artificial
satellite ever made. It orbits our planet 24/7 and houses at least 4-7 astronauts at any given
point. It has been up there for so long that astronauts are flown up to the space station,
where they replace other crew members and carry on their respective duties as part of
their assigned mission. A spacecraft like the International Space Station obviously doesn’t
carry years’ worth of oxygen with it, which is why it uses science to CREATE its own oxygen.
The primary method of generating breathable oxygen onboard the ISS revolves around
oxygen generators. There are two oxygen generators onboard the ISS—the American
Environmental Control and Life Support System (ECLSS) and the Russian Elektron.
So how do these oxygen generators produce breathable oxygen?
Ever heard of electrolysis? It’s a process that helps convert water into oxygen. You see,
a water molecule is composed of two hydrogen atoms and one oxygen atom. These two gases can
be separated through electrolysis, that is, by passing an electric current through the water.
Hydrogen gas is then vented into space and the oxygen gas is circulated within the cabin.
Getting electricity on board is not a problem; there is an ample supply of it,
thanks to the massive solar panels of the ISS. The electric current generated by the solar
panels is supplied to the oxygen generators through the space station’s power grid.
Water gets delivered to the ISS by supply ships sent from Earth. In addition to that,
water also gets reclaimed by condensers that remove water vapor from the cabin air. They
even use astronauts’ urine— filtering and recycling it to produce water.
The other way astronauts aboard the ISS get breathable oxygen is through delivery
packages sent from Earth. Various supply ships from space agencies are flown out to space,
where they make contact with the space station and deliver oxygen gas.
The third system of oxygen generation onboard the ISS is related to chemical
reactions. A system called the solid fuel oxygen generator, also known as ’perchlorate candles’,
consists of canisters that contain a mixture of powdered sodium chlorate and iron powder. When
the canister is ignited, the iron ‘burns’ and produces the heat energy required
for the chemical reaction. This reaction produces sodium chloride and oxygen gas.
According to NASA, each oxygen canister releases enough oxygen for one person for one day.
Interestingly, this is the same technology used in commercial
airplanes to produce breathable oxygen in the event of a drop in cabin air pressure.
In addition to providing breathable oxygen to the crew, it’s also imperative to ensure that the air
onboard the station is clean. Presently, carbon dioxide is removed from the air by
a machine called a ‘zeolite’, which acts as a ‘molecular sieve’. This gets rid of the waste
carbon dioxide exhaled by the astronauts. There are some other gases in the air too,
including methane, acetone, methyl alcohol and carbon monoxide.
These are removed with the help of activated charcoal filters aboard the station.
All in all, there is some really smart technology at work, and clever backups,
and then backups for those backups, all of which ensure that the crew aboard the ISS has plenty
of clean air to breathe so they can safely perform their duties and daily activities!