The Micro-Ecological Life Support System Alternative (MELiSSA) is a European Space Agency (ESA) initiative with the aim to develop the technology for a future regenerative life support system for long-term human space missions. Initiated in 1989, the design is inspired by a terrestrial ecosystem. As of 2023, MELiSSA is a consortium made up of 30 organisations across Europe. [1]
Space missions involving humans require essential resources to sustain life. Approximately 3.56 kg of drinkable water and 26 kg of water for hygiene is needed for each person. [2] The longer and further the missions are, the more difficult and costly it becomes to supply resources. MELiSSA's aim is to ideally create an artificially closed ecosystem to autonomously recycle the wastes to oxygen, water and food with only the input of energy to drive the process.
The loop is made up of 4 compartments with the crew members at the centre. The compartments are:
This compartment is the collection point for all mission waste, such as urea and kitchen waste, as well as the non-edible parts of the higher plant compartment (i.e. straw and roots). The compartment's aim is to anaerobically transform this waste to ammonium, H2, CO2, volatile fatty acids and minerals. For biosafety reasons and for optimum degradation efficiency, the compartment operates in thermophilic conditions (55 °C). The process of degradation in this compartment is carried out by proteolysis, saccharolysis and cellulolysis.
This compartment is responsible for the elimination of the terminal products of the liquefying compartment; mainly the volatile fatty acids.
The nitrifying compartment's main function is to cycle NH4+ produced from waste to nitrates, which is the most favourable source of nitrogen for higher plants as well as Arthrospira platensis . The compartment is composed of a mix of Nitrosomonas and Nitrobacter which oxidise NH4+ to NO2− and NO2− to NO3−, respectively. As this compartment is a fixed bed reactor, the importance of the hydrodynamic factors is slightly more important as well as more complicated.
The fourth compartment is split into two parts: the algae compartment, colonised by the cyanobacteria Arthrospira platensis, and the higher plant compartment. These compartments are essential for the regeneration of oxygen and the production of food.
A closed ecosystem can be thought of as a mass balance between the major elements, carbon, hydrogen, oxygen, nitrogen, sulphur and phosphorus (CHONSP), which alone represent 95% of the mass to recycle. The conversion of waste elements to resources, which can be used by crew members, can be achieved by two means: physiochemically or biologically. Physiochemical processes such as the Sabatier reaction would result in high efficiencies, but a large amount of energy is required in terms of temperature and pressure. In biological processes, using photosynthesis, efficiencies are lower, but ambient temperatures and pressures can be used. Photosynthesis is the process whereby plants convert light energy into chemical energy of sugars and other organic compounds. The chemical reactions utilise carbon and water with the by-product of oxygen, released into the atmosphere. MELiSSA is partly based on these photosynthetic reactions: recycling carbon dioxide into oxygen. Higher plants (wheat, rice, salad ingredients) would be utilised to produce food for the crew members. Photosynthetic micro-organisms would also be used to transform carbon dioxide into oxygen with the possibility of using the micro-organism of choice as part of the food intake, as an essential protein resource.
Unlike a natural ecosystem, which is regulated by the interaction of many different species; an artificially closed ecosystem has a reduced number of steps and it is sized and controlled to reach the desired objectives. It is akin to industrial processes, transforming raw materials into useful substances. However, one key difference is the targeted objective to recycle near 100% of wastes (limiting feed stock), essentially operating MELiSSA in a closed loop.
Achieving near 100% for the major elements is theoretical. When compared to natural ecosystems, even Earth is not a truly closed system: every year, thousands of tons of meteoric matter fall to Earth from space, while thousands of tons of hydrogen and helium escape Earth's atmosphere. Further, an artificial ecosystem is inherently dynamic; MELiSSA has to respond very quickly to changes in human behaviour. This requires a dynamic control system which is developed for each step of the process and the system as a whole.
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 MELiSSA Space Research Program – film highlights a brief introduction to the research program and information presented on the current Pilot Plant |
The current MELiSSA Pilot Plant is located at Universitat Autònoma de Barcelona and was inaugurated in 2009. [3] It is the place where the results obtained by the MELiSSA international team are integrated and tested. The final goal of the operation of the Pilot Plant is to demonstrate, evaluate and improve the feasibility of the MELiSSA loop concept on ground conditions, in order to guide the future developments towards a regenerative life support system for space applications.
University of Arizona Biosphere 2 is an American Earth system science research facility located in Oracle, Arizona. Its mission is to serve as a center for research, outreach, teaching, and lifelong learning about Earth, its living systems, and its place in the universe. It is a 3.14-acre (1.27-hectare) structure originally built to be an artificial, materially closed ecological system, or vivarium. It remains the largest closed ecological system ever created.
A life-support system is the combination of equipment that allows survival in an environment or situation that would not support that life in its absence. It is generally applied to systems supporting human life in situations where the outside environment is hostile, such as outer space or underwater, or medical situations where the health of the person is compromised to the extent that the risk of death would be high without the function of the equipment.
Closed ecological systems or contained ecological systems (CES) are ecosystems that do not rely on matter exchange with any part outside the system.
BIOS-3 is an experimental closed ecosystem at the Institute of Biophysics in Krasnoyarsk, Russia.
The Sabatier reaction or Sabatier process produces methane and water from a reaction of hydrogen with carbon dioxide at elevated temperatures and pressures in the presence of a nickel catalyst. It was discovered by the French chemists Paul Sabatier and Jean-Baptiste Senderens in 1897. Optionally, ruthenium on alumina makes a more efficient catalyst. It is described by the following exothermic reaction:
The activated sludgeprocess is a type of biological wastewater treatment process for treating sewage or industrial wastewaters using aeration and a biological floc composed of bacteria and protozoa. It is one of several biological wastewater treatment alternatives in secondary treatment, which deals with the removal of biodegradable organic matter and suspended solids. It uses air and microorganisms to biologically oxidize organic pollutants, producing a waste sludge containing the oxidized material.
Controlledecological life-support systems are a self-supporting life support system for space stations and colonies typically through controlled closed ecological systems, such as the BioHome, BIOS-3, Biosphere 2, Mars Desert Research Station, and Yuegong-1.
Nitrobacter is a genus comprising rod-shaped, gram-negative, and chemoautotrophic bacteria. The name Nitrobacter derives from the Latin neuter gender noun nitrum, nitri, alkalis; the Ancient Greek noun βακτηρία, βακτηρίᾱς, rod. They are non-motile and reproduce via budding or binary fission. Nitrobacter cells are obligate aerobes and have a doubling time of about 13 hours.
In oceanic biogeochemistry, the f-ratio is the fraction of total primary production fuelled by nitrate. The ratio was originally defined by Richard Eppley and Bruce Peterson in one of the first papers estimating global oceanic production. This fraction was originally believed significant because it appeared to directly relate to the sinking (export) flux of organic marine snow from the surface ocean by the biological pump. However, this interpretation relied on the assumption of a strong depth-partitioning of a parallel process, nitrification, that more recent measurements has questioned.
Secondary treatment is the removal of biodegradable organic matter from sewage or similar kinds of wastewater. The aim is to achieve a certain degree of effluent quality in a sewage treatment plant suitable for the intended disposal or reuse option. A "primary treatment" step often precedes secondary treatment, whereby physical phase separation is used to remove settleable solids. During secondary treatment, biological processes are used to remove dissolved and suspended organic matter measured as biochemical oxygen demand (BOD). These processes are performed by microorganisms in a managed aerobic or anaerobic process depending on the treatment technology. Bacteria and protozoa consume biodegradable soluble organic contaminants while reproducing to form cells of biological solids. Secondary treatment is widely used in sewage treatment and is also applicable to many agricultural and industrial wastewaters.
A primarylife support system (PLSS), is a device connected to an astronaut or cosmonaut's spacesuit, which allows extra-vehicular activity with maximum freedom, independent of a spacecraft's life support system. A PLSS is generally worn like a backpack. The functions performed by the PLSS include:
This is a glossary of environmental science.
The International Space Station (ISS) Environmental Control and Life Support System (ECLSS) is a life support system that provides or controls atmospheric pressure, fire detection and suppression, oxygen levels, proper ventilation, waste management and water supply. It was jointly designed and tested by NASA's Marshall Space Flight Center, UTC Aerospace Systems, Boeing, Lockheed Martin, and Honeywell, inc.
Microalgae or microscopic algae grow in either marine or freshwater systems. They are primary producers in the oceans that convert water and carbon dioxide to biomass and oxygen in the presence of sunlight.
Bioregenerative life support systems (BLSS) are artificial ecosystems consisting of many complex symbiotic relationships among higher plants, animals, and microorganisms. As the most advanced life support technology, BLSS can provide a habitation environment similar to Earth's biosphere for space missions with extended durations, in deep space, and with multiple crews. These systems consist of artificial ecosystems into which plants and microorganisms that allow oxygen production, carbon dioxide fixation of carbon, water purification, waste recycling, and production of foods. In these systems, photosynthetic organisms would be used as plants and algae that provide biomass for food and oxygen, as well as microorganisms that degrade and recycle waste compounds generated by human activity, as well as unused plant debris in food.
Angelo Vermeulen is a Belgian space systems researcher, biologist and artist. In 2009 he co-founded SEADS, an international transdisciplinary collective of artists, scientists, engineers, and activists Its goal is to reshape the future through critical inquiry and hands-on experimentation. Biomodd is one of their most well-known art projects and consists of a worldwide series of co-created interactive art installations in which computers coexist with internal living ecosystems. For the last ten years, he has been collaborating with the European Space Agency’s MELiSSA program on biological life support for space and in 2013 he was crew commander of one of the NASA-funded HI-SEAS Mars mission simulations in Hawai'i. Currently, he works at Delft University of Technology on advanced concepts for interstellar exploration. His work proposes a bio-inspired design approach to deal with the unpredictability inherent to interstellar travel. He is a Senior TED Fellow and was selected in 2017 as one of the Top 5 Tech Pioneers from Belgium by the newspaper De Tijd.
Lunar Palace 1, Moon Palace 1 or Yuegong-1 is a Chinese research facility for developing a Moon base. It is an environmentally closed facility where occupants can simulate a long-duration self-contained mission with no outside inputs other than power/energy.
Dissimilatory nitrate reduction to ammonium (DNRA), also known as nitrate/nitrite ammonification, is the result of anaerobic respiration by chemoorganoheterotrophic microbes using nitrate (NO3−) as an electron acceptor for respiration. In anaerobic conditions microbes which undertake DNRA oxidise organic matter and use nitrate (rather than oxygen) as an electron acceptor, reducing it to nitrite, and then to ammonium (NO3− → NO2− → NH4+).
Eu:CROPIS was a life science satellite developed by the German Aerospace Center (DLR) and intended to investigate the possibility of growing plants in different levels of gravity, such as that of the Moon and Mars, as a sustainable food source using human urine for moisture and as the source of fixed nitrogen.
The viral shunt is a mechanism that prevents marine microbial particulate organic matter (POM) from migrating up trophic levels by recycling them into dissolved organic matter (DOM), which can be readily taken up by microorganisms. The DOM recycled by the viral shunt pathway is comparable to the amount generated by the other main sources of marine DOM.
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