Scientists are developing technology to make sustainable space travel possible. As NASA prepares for long-term space missions Moon, March and beyond, many challenges remain. the future of space travel requires solutions for long-term missions with limited resources. They will need access to fuel and essentials for life. Scientists recently demonstrated a possible solution by dividing water into oxygen and hydrogen into zero gravity using semiconductor material and light.
Challenges for sustainable space travel
It’s already difficult for astronauts to live at the International Space Station (ISS) and it is a well-established station located nearby in low orbit. Longer missions will be even more delicate.
According to NASA, the ISS uses a system that recycles approximately 90% of the water and 42% of the oxygen in the spacecraft. The system purifies the crew’s waste – including urine and sweat – and turns it into potable water for the crew to drink. However, cargo spaceships regularly visit the space station to supplement essential supplies and replace some of the system components. How will future astronauts get the elements they need to survive in long-term space missions? What will power their spaceships and the electronic gadgets they will need on board?
Fuel cell space vehicles
The conversation reports that an international team of researchers has demonstrated that it is possible to produce hydrogen and oxygen from water using a semiconductor material and sunlight (or light from a star) in zero gravity. These results, which are published in Nature Communications, are a step towards a long-term space journey with storable renewable energy.
Although water can be a relatively heavy supply for space travel, it is a reasonable option as it provides a two-seater for one, with hydrogen for fuel and oxygen for astronauts to breathe. In addition, it can be recycled, making sustainable space travel possible. As a bonus, launching a space vehicle laden with water is safer than the potentially explosive alternative of rocket fuel and oxygen. For this idea to be realistic, scientists must develop a method to separate and replenish water. They are working on how to create water from oxygen and hydrogen, as well as the opposite.
In space, we don’t have the luxury of plants releasing oxygen, but we can imitate photosynthesis. According to the conversation, water can be divided into hydrogen and oxygen via electrolysis, where scientists pass an electric current through a sample of water that contains a soluble electrolyte.
A new version is even better for space travel because it uses light equipment and sunlight (or starlight). Although solar energy is useful on earth, it is even more abundant in space, where light is not filtered through an atmosphere. In this alternative method, the photocatalysts absorb photons in a semiconductor material in water.
The researchers explain in Nature, “The photoelectrochemical cell consists of an integrated semiconductor system functionalized by a catalyst that generates hydrogen.”
As a bonus which will be particularly useful with limited resources in space, the process can be reversed.
How to create water from oxygen and hydrogen
Hydrogen and oxygen can be recombined, according to the conversation, “using a fuel cell restoring the solar energy absorbed by photocatalysis”. This energy can be used to power the electronics and it produces water which can be reused.
Tower drop test
To test their system, the researchers placed their experiment in a 120-meter tower. As the object accelerated towards Earth, the “drop tower” simulates microgravity by creating an effect opposite to the G forces that the astronauts undergo during takeoff.
The bubble problem
While the researchers succeeded in dividing water into hydrogen and oxygen in this environment of microgravity, a great challenge appeared: the bubbles. When water is divided to create gas, bubbles form. On Earth, gravity floats the bubbles on the surface, but in zero gravity, the bubble hides near the catalyst, blocking the next potential bubble, and therefore obstructing the overall production of gas.
They tried to solve the bubble problem by creating pyramid-shaped areas on the catalyst so that the bubble could easily move from the pointed tip and float. But even if this has removed the bubbles from the catalyst, without gravity, they remain in the liquid and create a pesky foam which blocks the catalyst and the electrodes, making the whole system ineffective.
Despite these remaining challenges, the new method of water separation proves that there is great potential for sustainable space travel in the future. Advanced technologies and creative scientific processes can make the most of limited resources, on Earth and in space.