Life support system
A life support system refers to technologies or technology combinations that enable living beings to survive in environments in which their survival is actually not possible. Depending on the form of life, life support systems are required in different places, for example in relation to people in space or in the deep sea . On earth, the biosphere represents the life support system of living things.
functionality
Different systems are necessary for survival, depending on the environmental conditions and duration of use. While the compressed air cylinder and the diving suit of a diver can already be described as a life support system, more space and energy are required for more extensive, more comfortable or longer stay systems, which means either a stationary building or a vehicle ( spaceship , submarine ) is required.
The main functions of life support systems include the supply of breathing gas , air conditioning and water supply, as well as indirectly (since supplying the systems) the energy supply . Under extreme conditions such as in space or the deep sea, protection from harmful radiation or external pressure as well as fire detection and fighting are also included. The supply of food is not always counted directly as part of the tasks of a life support system, as this has so far only been made available through storage. In the case of Russian space technology, this is also included, while NASA speaks more of crew systems or crew habitation systems . In the case of future and longer-term dependence on life support systems, however, the inclusion of food supply is also necessary. One example is the simulation of such a system as part of Biosphere 2 and other similar projects.
For people, this means that per person at rest or in light activity per day around 800 g of oxygen, 2.5 l of drinking water and 700 g of food and, depending on the comfort and system, between 1 and 5 l of water for hygienic requirements and a corresponding amount of energy for air conditioning and care must be provided. These values increase depending on the working and usage conditions. Since the necessary stocks and waste quantities increase with the duration and the number of people, regeneration and processing in closed cycles is gaining in importance in this context , which describes the transition from open to closed systems. This means that the respective consumables are recovered from waste products through mostly multi-stage mechanical, physical or chemical processes. Depending on the operating conditions and the raw materials available, a direct synthesis (such as the extraction of oxygen and water from seawater on board submarines) is also possible. The corresponding source and waste materials must be stored, distributed, regenerated or disposed of, for which purpose appropriate equipment must be provided in the construction of a life support system. This requires, for example, refrigerators, tanks, pipes, pumps, measurement and monitoring technology.
Breathing gas and air conditioning
In order to enable people to survive, the supply of breathable gas (i.e. air) must be ensured. For this, the air must be as free of pollutants as possible and comply with certain parameters. A total pressure of 97.9 to 102.7 kPa , an oxygen partial pressure of 19.5 to 23.1 kPa, a nitrogen partial pressure of less than 80 kPa and a carbon dioxide partial pressure of less than 1 are on board the ISS kPa considered acceptable. The air temperature in the ISS is (adjustable) between 18.3 and 26.7 ° C. The air conditioning ensures a humidity between 25 and 75% and a constant air movement between 0.05 and 1.0 m / s in order to avoid microbe growth and mold formation on the one hand and air that is too dry (risk of sparks) on the other. Conventional air conditioning systems with refrigerants (e.g. ammonia or freon) are mostly used here. Condensing heat exchangers are used to dehumidify the air . Reusable zeolites or solid amines are used to bind carbon dioxide, and lithium hydroxide is used in space suits . The production of oxygen is usually done by the electrolysis of water and partially recovering from the carbon dioxide by Sabatier reaction and subsequent methane - pyrolysis . As a backup or for short-term use, compressed oxygen or chemical reactions to deliver oxygen are also used. Pollutants are constantly monitored using appropriate measuring methods such as mass spectrometers and gas chromatography and filtered out using molecular sieves, activated carbon or lithium hydroxide. Similar values apply in submarines and similar processes are sometimes used.
Water treatment
For the production of drinking water , but also of water for technical use (such as experiments, fuel cells , hygiene ...), different systems are used depending on the requirements. In submarines, drinking water can be obtained directly from the environment by desalination of seawater . In space stations, reprocessing systems are used that extract water from the cabin air by condensation , the waste water (hygiene, experiments ...) and the urine of the space travelers. Corresponding water treatment systems ( e.g. sorption or ion exchangers ) and additional preservatives (e.g. iodine or silver oxide ) are used here for service water and condensate . Special exist for the reprocessing of urine Space toilets that only with aggressive chemicals such as ozone and sulfuric acid , a formation of ammonia suppress (odor) and then the urine by distillation to convert to water.
Crew Systems
This part of the life support system includes all things that are directly related to work and the well-being of people or living beings. This is especially necessary in the case of long-term dependence on life support systems. This includes all things personal hygiene , food supply, preparation and storage, waste treatment, medical care (this also includes sports equipment), clothing and more. In the case of food, attention must be paid to the shelf life of the food and a supply of all essential substances such as vitamins and minerals . When supplying food in space, due to the weightlessness (risk of inhalation and accumulation in filters and devices), any form of powdery substances (sugar, salt ...) and crumbly food should be avoided.
Examples of life support systems
Individual evidence
- ↑ Heinz Mielke; transpress lexicon space research; VLN 162-925 / 123/86
- ↑ a b c Willi Hallmann, Wilfried Ley and Klaus Wittmann; Space Technology Handbook; ISBN 978-3-446-41185-2