Space travel, especially to the most distant planets, requires self-sufficiency in oxygen, water and food. No external source can be imported into these shuttles en route! That' s why microalgae - so small, so powerful and so nutritious - are currently the subject of serious scientific study, with the aim of accompanying future astronauts on their journeys.
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SPACE ADVENTURE, TECHNICAL CONSTRAINTS
For flights lasting a few days, it's easy to provide the necessary supplies for the occupants of the spacecraft, while maintaining sufficient storage space for waste. However, for journeys lasting several months, far away and therefore without refuelling, such as to Mars, this logistical aspect becomes a real constraint, especially in terms of weight. A human organism uses at least 5 kg of water, food and oxygen per day, and produces a great deal of gaseous, liquid and solid waste. Since the tonnage to be transported is proportional to the duration of the journey, there are two solutions: increase the power of launchers to enable the tonnage required for life to be sent over several months, or provide highly concentrated nutritional resources and set up an autonomous system for recycling the waste produced by these space travellers.
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THE MELISSA PROJECT, A CLOSED, ECONOMICAL ECOSYSTEM
The European Space Agency, through its Melissa1 (Micro-Ecological Life Support Alternative) project, is aiming for the latter solution, having been studying for over 25 years the possibility of creating a closed, self-sufficient ecosystem inside space ships.
Spirulina appears to be particularly well-suited to this type of mission. Indeed, microalgae are doubly interesting: they have the capacity to transform fatty acids and carbon dioxide (CO2) into oxygen (O2 ), and are particularly interesting as high-quality nutritional supplements. However, there are many constraints in space that do not exist on Earth. The absence of natural reserves (oceans, soil, atmosphere) and the presence of radiation lead to rapid evolution of micro-organisms. These autonomous systems are essential for keeping astronauts alive, and therefore need to be fully operational before they can be used. Tests are currently being carried out both on Earth and in space to find the right balance and guarantee their effectiveness.
FEEDING ASTRONAUTS: A "MICRO" CHALLENGE
In order to be taken on board, food must meet a number of criteria, including being crumb-free, pasteurized to avoid on-board contamination, and tasty, as the sense of taste is diminished in weightlessness. But they also have to be compact, light and nutritious. These last three criteria are difficult to meet for everyday foods. Indeed, for the vast majority of them, the nutritional intake is sufficient for a relatively large quantity, and therefore rather space-consuming. So why not supplement rations with spirulina, which is compact, light and highly nutritious?
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By way of comparison, to provide around 25g of high-biological-value proteins, you would need to consume 100g of meat, compared with just 35g of spirulina. And as the average 70kg astronaut would need to consume around 220g of meat, by dividing the ration by 2 and supplementing with spirulina, we would already gain over 2kg of weight for 1 month. That may not sound like much, but when every gram counts, it can quickly add up. When you also know that spirulina is rich in vitamins and minerals, there's no doubt that microalgae will have a place in future space odysseys.
And if one day man really does walk on Mars, it will undoubtedly be thanks to micro-algae!