Space agencies are no stranger to hydrogen as a fuel or propellant. The Centaur and Apollo launches and even the space shuttle relied on liquid hydrogen to carry them into orbit. The average launch would burn more than 500,000 gallons of liquid hydrogen, losing another 239,000 gallons in boil-off and transfer.
Hydrogen is an efficient fuel and doesn’t generate CO2, though it can lead to nitrogen oxide or NOx generation. Unfortunately, it isn’t the best option for long-term missions or long-distance space flights.
Fuel cells could help bridge the gap and make it easier for humans to spend more time in outer space.
Fuel Cells on the Space Shuttle
The space shuttle program conducted operations from 1972 until its final flight in 2011, carrying astronauts into orbit on more than 130 missions. They utilized a hydrogen fuel cell that helped power the craft while in orbit.
A fuel cell power plant contained 96 individual cells arranged in three substacks of 32. These substacks provided extra layers of redundancy. Each cell could generate between 7,000 and 12,000 watts for 15 minutes, but they weren’t all necessary to power the space shuttle. A single fuel cell system was more than enough to keep the shuttle operating until the astronauts could make repairs or return to Earth.
Unfortunately, these fuel cells aren’t safe. The fuel cell stored the electrolyte mixture in an asbestos matrix and contained potassium hydroxide. The caustic chemical could seep through the asbestos fibers, creating health concerns for anyone who worked around the fuel cells.
This technology might be obsolete, but that doesn’t mean that NASA has abandoned the idea of fuel cells altogether.
Fuel Cells vs. Batteries
What is the difference between a fuel cell and a battery? Fuel cells can generate electricity, while batteries can only store it. They do share some similarities, though. Some batteries can be recharged, just like some fuel cells can be refueled.
Fuel cells, especially ones that run on hydrogen, also function better in outer space. A battery capable of generating 250 watts continuously might only work for a month or two. In contrast, a fuel cell stack of comparable size could create the same electricity for one or two years. This could prove invaluable for long-term space applications, where every kilogram of cargo costs money to launch.
Hydrogen Fuel Cells for Space Travel
The European Space Agency (ESA), alongside the Canadian Space Agency (CSA) and the Japanese Aerospace Exploration Agency (JAXA), is already working on hydrogen fuel cells that could be sent to space. HERACLES (Human-Enhanced Robotic Architecture for Lunar Exploration and Science) is a planned robotic mission that will deposit the European Large Logistic Lander (EL3) on the lunar surface.
In addition to collecting information about the moon, this lander will serve as a support service for NASA’s Artemis missions planned for 2024 or 2025.
HERACLES will be equipped with regenerative fuel cells. This closed-loop system produces hydrogen and oxygen from water. Later, these elements are fed back into the fuel cell to produce electricity, creating water again. The system can then reclaim the water and start the cycle over again. It will be capable of generating heat and electricity that will be necessary to help the craft withstand the long and bitterly cold lunar nights.
This system will eventually fail, but these regenerative fuel cells can support human and robotic space travel for infinitely longer than a battery.
Looking Toward the Stars
Humans are venturing further into the cosmos and will need better fuel options to keep warm in the cold and provide light. Hydrogen fuel cells are one of the best options available today and have even greater future potential.
Jane Marsh, Contributor
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