More than just rocket science – hidden chemical forces underpin launching the moon and sustaining life in space
Millions of people around the world will be eagerly watching Saturday as NASA launches Artemis I, the first lunar exploration mission since the 1970s.
This spectacle includes the Space Launch System (SLS), the world’s most powerful rocket. At nearly 100 meters tall and weighing more than 2,600 tons, the SLS produces a massive 8.8 million pounds of thrust (more than 31 times the thrust of a Boeing 747 jet).
But there’s more than just amazing engineering behind rocket science and space exploration. Hidden within it is the ingenious chemistry that powers these wonderful feats and sustains fragile life in space.
Read more: NASA launches first phase of Artemis mission – this is why humans are returning to the moon
fuel and spark
To launch a rocket into space, a chemical reaction called combustion is required. Here the fuel combines with the oxygen, resulting in the production of energy. That energy, in turn, provides the necessary push (or thrust) to propel massive machines like the SLS into the Earth’s upper atmosphere and beyond.
Rockets, like cars on the road and jets in the air, have engines in which combustion takes place. In the SLS he has two engine systems. Four core stage RS-25 engines (upgraded Space Shuttle engines) and two solid rocket boosters. And chemistry is what gives each engine its own fuel mixture.
Core stage engines use a mixture of liquid oxygen and liquid hydrogen, while solid rocket boosters, as the name suggests, contain a solid propellant—a hard, rubber-like material called polybutadiene-acrylonitrile. In addition to being the fuel itself, this material contains fine particles of aluminum metal as the fuel and ammonium perchlorate as the oxygen source.
Solid rocket booster fuels are easy to store at room temperature, but core stage engine fuels must be stored at -253°C for liquid hydrogen and -183°C for liquid oxygen. So you can see sheets of ice peeling off the rocket during launch. The fuel container is so cold that moisture freezes from the surrounding air.
But there is another interesting chemical reaction that takes place when the fuel needs to be ignited. Depending on the fuel source, the rocket can be ignited electrically via glorious spark plugs or chemically.
If you’ve seen space launches and heard talk about “TEA-TEB ignition”, it refers to triethylaluminum and triethylborane. These two chemicals are pyrophoric. This means that it can spontaneously ignite when exposed to air.
sustain life among the stars
Rockets aren’t the only ones fueled by chemistry. Life support systems in space rely on chemical processes to keep astronauts alive and breathing.
We all know the importance of oxygen, but when we breathe we exhale carbon dioxide as a toxic waste product. What about carbon dioxide?
Remember when Tom Hanks tried to fit the square pegs into the round holes in the movie Apollo 13? It was a scrubber.
These scrubbers are disposable filters packed with lithium hydroxide (similar to the chemical found in drain cleaning fluid) that captures carbon dioxide gas via a simple acid-base chemistry. These scrubbers remove carbon dioxide very efficiently, allowing astronauts to breathe easily, but the filters have limited capacity. Once saturated, it becomes ineffective.
Therefore, it is impractical to use lithium hydroxide filters for extended space missions. Scientists later developed a system that uses a reusable carbon dioxide scrubber made from a mineral called zeolite. Using zeolites releases trapped carbon dioxide into space, leaving the filter free to trap gas.
But in 2010, scientists discovered an even better way to manage carbon dioxide. It is to turn this waste into another vital element of life: water.
From waste to resources
The ISS environmental control and life support system replaces the carbon dioxide scrubber with a carbon dioxide abatement system, also known as the Sabatier system. It is named for the chemical reaction central to its function and is named after its discoverer, Paul Sabatier, who won the Nobel Prize in Chemistry in 1912.
The system combines carbon dioxide and hydrogen gas to produce water and methane. Methane gas is released into space, and through a process called hydrolysis, water breaks down into breathable oxygen and hydrogen gases. The latter is recycled, converting more carbon dioxide into water.
This process is not only useful for space exploration. Closer to home, chemists are investigating similar systems that could potentially address greenhouse gas emissions. It’s not a panacea, but the Sabatier reaction could help recycle some of the Earth’s carbon dioxide.
Meanwhile, NASA’s Artemis Moon mission aims to land the first woman and people of color on the moon and establish long-term human presence on a lunar base. The Sabatier reaction and other lesser-known chemical processes will be key to humanity’s continued commitment to space.
Read more: Artemis I mission marks the beginning of a new space race to mine the moon