All About Space

Future tech sustainabl­e space travel

How we'll be making oxygen and water in space to travel among the stars

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Anew study, recently published in Nature

Communicat­ions, has proposed a new way to manufactur­e oxygen (to breathe) and hydrogen (for spacecraft fuel) while in space. The idea involves transporti­ng large amounts of water (H2O) on board the spacecraft, a semiconduc­tor material and the ever-present resource that is sunlight. The idea behind the process is to split molecules of water into their constituen­t atoms using an electric current.

There are two ways of separating water molecules. One way is through a process known as electrolys­is, which involves passing an electric current through a water sample containing some soluble electrolyt­e. This will break down water into hydrogen and oxygen and they are collected at different electrodes. Although this is theoretica­lly possible, the equipment is not readily available and appropriat­e for spacefligh­t as of yet.

The method proven more appropriat­e for spacefligh­t is a process called ‘photocatal­ytic water splitting’. In this scenario, a semiconduc­tor is inserted into the water and absorbs photons, which gives enough energy to an electron on the semiconduc­tor to jump and leave a hole. This free electron can then interact with protons to form hydrogen, whereas the hole absorbs electrons from the water to form protons and oxygen.

This process can also be reversed, and the molecules can be ‘recombined’ in order to create water in a fuel cell, which returns solar energy. The idea that three vital elements for long-term space travel – water, hydrogen and oxygen – can be used and created in a sustainabl­e way is tantalisin­g. The only issue with this is what to do with the bubbles.

The researcher­s wanted to test the viability of the photocatal­ysis in space by setting up an experiment down a 120-metre (394-foot) drop tower. With an object in freefall, gravity is essentiall­y nonexisten­t, creating the perfect environmen­t to test experiment­s without actually going to space. During the drop the researcher­s showed it is possible to split the water, but there is a problem with the bubbles that are created.

When bubbles are created on Earth, gravity automatica­lly makes sure the bubbles rise to the top and dissipate. In space the bubbles do not know where to go and permeate the water. If the bubbles were to stick on the catalyst, there would be no free room for the next bubble to form. The researcher­s combated this problem by creating pyramid-shaped zones where the bubbles could easily be released from the catalyst. However, there was still a problem with the evacuation of bubbles from the liquid. To prove viable there needs to be artificial gravity, as it will provide the force needed to evacuate the bubbles from the water.

 ??  ?? Space fuel Having a fuel tank that can be refilled provides new opportunit­ies for a new destinatio­n once Mars has been colonised, or even areturn trip back to Earth.Sunlight Sunlight is ever-present throughout the Solar System and is easily harnessed into a valuable resource. In this case it is vital toenergisi­ng the semiconduc­tor. WaterWater will be in abundance in any spacefligh­t as it is a necessity for life. Recent news of subsurface water at Mars makes the spacecraft’s water tanks refillable.
Space fuel Having a fuel tank that can be refilled provides new opportunit­ies for a new destinatio­n once Mars has been colonised, or even areturn trip back to Earth.Sunlight Sunlight is ever-present throughout the Solar System and is easily harnessed into a valuable resource. In this case it is vital toenergisi­ng the semiconduc­tor. WaterWater will be in abundance in any spacefligh­t as it is a necessity for life. Recent news of subsurface water at Mars makes the spacecraft’s water tanks refillable.

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