Method of manufacture of water oxygen in zero gravity raises hope for long-distance space travel

Sun power

The hydrogen and oxygen thus produced from water could also serve as fuel to a spacecraft. Throwing a rocket with water would actually be much safer than throwing it with extra rocket fuel and oxygen on board, which can be explosive. Once in space, a special technology could divide the water into hydrogen and oxygen, which in turn could be used to sustain life or fuel the electronics via fuel cells.

There are two options for doing this. One involves electrolysis as we do on Earth, using electrolytes and solar cells to capture sunlight and convert it into current.

The alternative is to use "photocatalysts", which act by absorbing light particles – photons – into a semiconductor material inserted into the water. The energy of a photon is absorbed by an electron in the material that jumps, leaving behind a hole. The free electron can react with the protons (which form the atomic nucleus with the neutrons) in the water to form hydrogen. Meanwhile, the hole can absorb electrons from the water to form protons and oxygen.

The process can also be reversed. Hydrogen and oxygen can be collected or "recombined" by using a fuel cell returning solar energy absorbed by the "photocatalysis" – energy that can be used to power the electronics . Recombination only forms water as a product, which means that water can also be recycled. This is the key to long-distance space travel.

The process using photo-catalysts is the best option for traveling in space because the equipment weighs much less than that needed for electrolysis. In theory, it should work easily. This is partly because the intensity of sunlight is much higher without the Earth's atmosphere absorbing large amounts of it

Bubble management

In the new study, researchers abandoned the complete experimental setup for photocatalysis in a 120-meter tower, creating an environment similar to microgravity. As objects accelerate toward the Earth in free fall, the effect of gravity decreases when the forces exerted by gravity are canceled by equal and opposite forces due to acceleration. This is in contrast to the G forces experienced by astronauts and fighter pilots who accelerate in their aircraft.

The researchers were able to show that it is actually possible to divide the water in this environment. However, when the water is split to create gas, bubbles form. Getting rid of the bubbles of the catalytic material once formed is important – bubbles interfere with the process of gas creation. On Earth, gravity automatically floats bubbles on the surface (the water near the surface is denser than the bubbles, making them more active), thus freeing up space on the catalyst for produce the next bubble.

In zero gravity, this is not possible and the bubble will stay on or near the catalyst. However, scientists have adjusted the shape of the nanoscale features in the catalyst by creating pyramid-shaped areas where the bubble could easily disengage from the tip and float in the middle.

But a problem remains. In the absence of gravity, the bubbles will remain in the liquid – even if they have been expelled from the catalyst itself. Gravity allows gases to escape easily from the liquid, which is essential for the use of pure hydrogen and oxygen. Without the presence of gravity, no bubble of gas floats on the surface and separates from the mixture – instead all the gas remains to create a foam.

This greatly reduces the efficiency of the process by blocking catalysts or electrodes. The engineering solutions around this problem will be the key to the successful implementation of technology in the space – with a possibility to use the centrifugal forces of the rotation of one. spacecraft to separate the gases from the solution.

to long-lived human space flights.

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