The Momsen lung was a primitive underwater rebreather used before and during World War II by American submariners as emergency escape gear. It was invented by Charles Momsen , who worked on it from 1929 to 1932. Submariners trained with this apparatus in an 80 ft (24 m) deep Escape Training Tank at New London , Mare Island , or Pearl Harbor . It was introduced as standard equipment on Porpoise (P) -class and Salmon -class boats.
82-489: The device recycled the breathing gas by using a counterlung containing soda lime to remove the carbon dioxide . The lung was initially filled with oxygen and connected to a mouthpiece by twin hoses containing one-way valves, one for breathing in and the other for breathing out. The only known emergency use of the Momsen lung was during the escape from USS Tang on October 25, 1944. Thirteen men (of thirty survivors) left
164-673: A saturation diving system is considered a life-support system – the personnel who are responsible for operating it are called life support technicians . The concept can also be extended to submarines , crewed submersibles and atmospheric diving suits , where the breathing gas requires treatment to remain respirable, and the occupants are isolated from the outside ambient pressure and temperature. Medical life-support systems include heart-lung machines , medical ventilators and dialysis equipment. A crewmember of typical size requires approximately 5 kilograms (11 lb) of food , water , and oxygen per day to perform standard activities on
246-550: A fire hazard, so the more successful applications have been for space-suits, fire-fighting and mine rescue. A liquid oxygen supply can be used for oxygen or mixed gas rebreathers. If used underwater, the liquid-oxygen container must be well insulated against heat transfer from the water. Industrial sets of this type may not be suitable for diving, and diving sets of this type may not be suitable for use out of water due to conflicting heat transfer requirements. The set's liquid oxygen tank must be filled immediately before use. Examples of
328-465: A highly integrated and reliable system: Air temperature control, Humidity removal, Carbon dioxide removal , Trace contaminant removal, Post-fire atmospheric recovery, Air filtration, and Cabin air circulation. Space station systems include technology that enables humans to live in outer space for a prolonged period of time. Such technology includes filtration systems for human waste disposal and air production. Skylab used 72% oxygen and 28% nitrogen at
410-417: A large range of options are available depending on the specific application and available budget. A diving rebreather is safety-critical life-support equipment – some modes of failure can kill the diver without warning, others can require immediate appropriate response for survival. A helium reclaim system (or push-pull system) is used to recover helium based breathing gas after use by the diver when this
492-411: A long beam extending another cabin section or counterweight, spinning it at an appropriate speed will cause centrifugal force to simulate the effect of gravity. If ω is the angular velocity of the ship's spin, then the acceleration at a radius r is: Notice the magnitude of this effect varies with the radius of rotation, which crewmembers might find inconvenient depending on the cabin design. Also,
574-404: A loop configured machine has two unidirectional valves so that only scrubbed gas flows to the patient while expired gas goes back to the machine. The anaesthetic machine can also provide gas to ventilated patients who cannot breathe on their own. A waste gas scavenging system removes any gasses from the operating room to avoid environmental contamination. One of the functions of a space suit
656-456: A lower pressure in the suit which gives the wearer better freedom of movement. Submarines , underwater habitats , bomb shelters, space stations , and other living spaces occupied by several people over medium to long periods on a limited gas supply, are equivalent to closed circuit rebreathers in principle, but generally rely on mechanical circulation of breathing gas through the scrubbers. Life-support system A life-support system
738-550: A naturally hypoxic environment. They need to be lightweight and to be reliable in severe cold including not getting choked with deposited frost. A high rate of system failures due to extreme cold has not been solved. Breathing pure oxygen results in an elevated partial pressure of oxygen in the blood: a climber breathing pure oxygen at the summit of Mount Everest has a greater oxygen partial pressure than breathing air at sea level. This results in being able to exert greater physical effort at altitude. The exothermic reaction helps keep
820-435: A number of hoses and electrical cables twisted together and deployed as a unit. This is extended to the divers through the diver umbilicals. The accommodation life support system maintains the chamber environment within the acceptable range for health and comfort of the occupants. Temperature, humidity, breathing gas quality, sanitation systems, and equipment function are monitored and controlled. An atmospheric diving suit
902-454: A pendulum rebreather. Breathing hoses can be tethered down to a diver's shoulders or ballasted for neutral buoyancy to minimise loads on the mouthpiece. A mouthpiece with bite-grip , an oro-nasal mask , a full-face mask , or a sealed helmet is provided so that the user can breathe from the unit hands-free. A store of oxygen, usually as compressed gas in a high pressure cylinder, but sometimes as liquid oxygen , that feeds gaseous oxygen into
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#1732901151705984-553: A space mission, and outputs a similar amount in the form of waste solids, waste liquids, and carbon dioxide . The mass breakdown of these metabolic parameters is as follows: 0.84 kg (1.9 lb) of oxygen, 0.62 kg (1.4 lb) of food, and 3.54 kg (7.8 lb) of water consumed, converted through the body's physiological processes to 0.11 kg (3.9 oz) of solid wastes, 3.89 kg (8.6 lb) of liquid wastes, and 1.00 kg (2.20 lb) of carbon dioxide produced. These levels can vary due to activity level of
1066-575: A specific mission assignment, but must obey the principle of mass balance . Actual water use during space missions is typically double the given value, mainly due to non-biological use (e.g. showering). Additionally, the volume and variety of waste products varies with mission duration to include hair, finger nails, skin flaking, and other biological wastes in missions exceeding one week in length. Other environmental considerations such as radiation, gravity, noise, vibration, and lighting also factor into human physiological response in outer space, though not with
1148-411: A surface saturation accommodation facility provides breathing gas and other services to support life for the personnel under pressure. It includes the following components: Underwater habitats differ in that the ambient external pressure is the same as internal pressure, so some engineering problems are simplified. Underwater habitats balance internal pressure with the ambient external pressure, allowing
1230-655: A total pressure of 5 psi. The Salyut and Mir space stations contained an air-like Oxygen and Nitrogen mixture at approximately sea-level pressures of 93.1 kPa (13.5psi) to 129 kPa (18.8 psi) with an Oxygen content of 21% to 40%. The life-support system for the Bigelow Commercial Space Station is being designed by Bigelow Aerospace in Las Vegas, Nevada . The space station will be constructed of habitable Sundancer and BA 330 expandable spacecraft modules. As of October 2010, " human-in-the-loop testing of
1312-514: A type of self-contained underwater breathing apparatus which have provisions for both a primary and emergency gas supply. On land they are used in industrial applications where poisonous gases may be present or oxygen may be absent, firefighting , where firefighters may be required to operate in an atmosphere immediately dangerous to life and health for extended periods, in hospital anaesthesia breathing systems to supply controlled concentrations of anaesthetic gases to patients without contaminating
1394-517: A vehicle or non-mobile installation is more likely to be referred to as a life-support system . Rebreather technology may be used where breathing gas supply is limited, such as underwater, in space, where the environment is toxic or hypoxic (as in firefighting), mine rescue, high-altitude operations, or where the breathing gas is specially enriched or contains expensive components, such as helium diluent or anaesthetic gases. Rebreathers are used in many environments: underwater, diving rebreathers are
1476-425: A wide enough bore to minimise flow resistance at the ambient pressure in the operational range for the equipment, are usually circular in cross section, and may be corrugated to let the user's head move about without the tube collapsing at kinks. Each end has an airtight connection to the adjacent component, and they may contain a one-way valve to keep the gas circulating the right way in a loop system. Depending on
1558-451: Is a European Space Agency led initiative, conceived as a micro-organisms and higher plants based ecosystem intended as a tool to gain understanding of the behaviour of artificial ecosystems, and for the development of the technology for a future regenerative life-support system for long term crewed space missions. CyBLiSS ("Cyanobacterium-Based Life Support Systems") is a concept developed by researchers from several space agencies ( NASA ,
1640-422: Is a breathing apparatus that absorbs the carbon dioxide of a user's exhaled breath to permit the rebreathing (recycling) of the substantially unused oxygen content, and unused inert content when present, of each breath. Oxygen is added to replenish the amount metabolised by the user. This differs from open-circuit breathing apparatus, where the exhaled gas is discharged directly into the environment. The purpose
1722-435: Is a small one-man articulated submersible of roughly anthropomorphic form, with limb joints which allow articulation under external pressure while maintaining an internal pressure of one atmosphere. Breathing gas supply may be surface supplied by umbilical, or from a rebreather carried on the suit. An emergency gas supply rebreather may also be fitted to a suit with either surface supply or rebreather for primary breathing gas. As
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#17329011517051804-402: Is calcium hydroxide, which is relatively cheap and easily available. Other components may be present in the absorbent. Sodium hydroxide is added to accelerate the reaction with carbon dioxide. Other chemicals may be added to prevent unwanted decomposition products when used with standard halogenated inhalation anaesthetics. An indicator may be included to show when carbon dioxide has dissolved in
1886-411: Is consumed by crew members for drinking, cleaning activities, EVA thermal control, and emergency uses. It must be stored, used, and reclaimed (from waste water and exhaled water vapor) efficiently since no on-site sources currently exist for the environments reached in the course of human space exploration. Future lunar missions may utilize water sourced from polar ices; Mars missions may utilize water from
1968-399: Is done, for example, by composting toilets which reintegrate waste material (excrement) back into the system, allowing the nutrients to be taken up by the food crops. The food coming from the crops is then consumed again by the system's users and the cycle continues. The logistics and area requirements involved however have been prohibitive in implementing such a system to date. Depending on
2050-420: Is important, such as in space stations and space suits. Lithium peroxide also replenishes the oxygen during the scrubbing reaction. Another method of carbon dioxide removal occasionally used in portable rebreathers is to freeze it out, which is possible in a cryogenic rebreather which uses liquid oxygen. The liquid oxygen absorbs heat from the carbon dioxide in a heat exchanger to convert the oxygen to gas, which
2132-613: Is less of a problem. The Soviet IDA71 rebreather was also manufactured in a high altitude version, which was operated as an oxygen rebreather. Anaesthetic machines can be configured as rebreathers to provide oxygen and anaesthetic gases to a patient during surgery or other procedures that require sedation. An absorbent is present in the machine to remove the carbon dioxide from the loop. Both semi-closed and fully closed circuit systems may be used for anaesthetic machines, and both push-pull (pendulum) two directional flow and one directional loop systems are used. The breathing circuit of
2214-427: Is more economical than losing it to the environment in open circuit systems. The recovered gas is passed through a scrubber system to remove carbon dioxide, filtered to remove odours, and pressurised into storage containers, where it may be mixed with oxygen to the required composition for re-use, either immediately, or at a later date. The life support system provides breathing gas and other services to support life for
2296-399: Is sufficient to freeze the carbon dioxide. This process also chills the gas, which is sometimes, but not always, desirable. A breathing hose or sometimes breathing tube on a rebreather is a flexible tube for breathing gas to pass through at ambient pressure. They are distinguished from the low-, intermediate-, and high-pressure hoses which may also be parts of rebreather apparatus. They have
2378-411: 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
2460-427: Is the earliest type of rebreather and was commonly used by navies for submarine escape and shallow water diving work, for mine rescue, high altitude mountaineering and flight, and in industrial applications from the early twentieth century. Oxygen rebreathers can be remarkably simple and mechanically reliable, and they were invented before open-circuit scuba. They only supply oxygen, so there is no requirement to control
2542-522: Is then available again to react with more carbonic acid. 100 grams (3.5 oz) of this absorbent can remove about 15 to 25 litres (0.53 to 0.88 cu ft) of carbon dioxide at standard atmospheric pressure. This process also heats and humidifies the air, which is desirable for diving in cold water, or climbing at high altitudes, but not for working in hot environments. Other reactions may be used in special circumstances. Lithium hydroxide and particularly lithium peroxide may be used where low mass
Momsen lung - Misplaced Pages Continue
2624-408: Is to extend the breathing endurance of a limited gas supply, while also eliminating the bubbles otherwise produced by an open circuit system. The latter advantage over other systems is useful for covert military operations by frogmen , as well as for undisturbed observation of underwater wildlife. A rebreather is generally understood to be a portable apparatus carried by the user. The same technology on
2706-427: Is to provide the wearer with breathing gas. This can be done via an umbilical from the life-support systems of the spacecraft or habitat, or from a primary life support system carried on the suit. Both of these systems involve rebreather technology as they both remove carbon dioxide from the breathing gas and add oxygen to compensate for oxygen used by the wearer. Space suits usually use oxygen rebreathers as this allows
2788-421: Is usually necessary to eliminate the metabolic product carbon dioxide (CO 2 ). The breathing reflex is triggered by CO 2 concentration in the blood, not by the oxygen concentration, so even a small buildup of CO 2 in the inhaled gas quickly becomes intolerable; if a person tries to directly rebreathe their exhaled breathing gas, they will soon feel an acute sense of suffocation , so rebreathers must remove
2870-542: Is wasted. Continued rebreathing of the same gas will deplete the oxygen to a level which will no longer support consciousness, and eventually life, so gas containing oxygen must be added to the breathing gas to maintain the required concentration of oxygen. However, if this is done without removing the carbon dioxide, it will rapidly build up in the recycled gas, resulting almost immediately in mild respiratory distress, and rapidly developing into further stages of hypercapnia , or carbon dioxide toxicity. A high ventilation rate
2952-796: The German Aerospace Center and the Italian Space Agency ) which would use cyanobacteria to process resources available on Mars directly into useful products, and into substrates for other key organisms of Bioregenerative life support system (BLSS). The goal is to make future human-occupied outposts on Mars as independent of Earth as possible (explorers living "off the land"), to reduce mission costs and increase safety. Even though developed independently, CyBLiSS would be complementary to other BLSS projects (such as MELiSSA) as it can connect them to materials found on Mars, thereby making them sustainable and expandable there. Instead of relying on
3034-569: The Soyuz spacecraft is called the Kompleks Sredstv Obespecheniya Zhiznideyatelnosti (KSOZh) ( Russian : Комплекс Средств Обеспечения Жизнедеятельности (KCOЖ) ). Vostok, Voshkod and Soyuz contained air-like mixtures at approximately 101kPa (14.7 psi). The life support system provides a nitrogen/oxygen atmosphere at sea level partial pressures. The atmosphere is then regenerated through KO2 cylinders, which absorb most of
3116-419: The decompression status of the diver and record the dive profile . As a person breathes, the body consumes oxygen and produces carbon dioxide . Base metabolism requires about 0.25 L/min of oxygen from a breathing rate of about 6 L/min, and a fit person working hard may ventilate at a rate of 95 L/min but will only metabolise about 4 L/min of oxygen. The oxygen metabolised is generally about 4% to 5% of
3198-444: The CO 2 in a component known as a carbon dioxide scrubber . By adding sufficient oxygen to compensate for the metabolic usage, removing the carbon dioxide, and rebreathing the gas, most of the volume is conserved. The endurance of a rebreather, the duration for which it can be safely and comfortably used, is dependent on the oxygen supply at the oxygen consumption rate of the user, and
3280-552: The CO2 and water produced by the crew biologically and regenerates the oxygen, the LiOH cylinders then absorb the leftover CO2. The Paragon Space Development Corporation is developing a plug and play ECLSS called commercial crew transport-air revitalization system (CCT-ARS) for future spacecraft partially paid for using NASA's Commercial Crew Development ( CCDev ) funding. The CCT-ARS provides seven primary spacecraft life support functions in
3362-821: The Space Shuttle, NASA includes in the ECLSS category systems that provide both life support for the crew and environmental control for payloads. The Shuttle Reference Manual contains ECLSS sections on: Crew Compartment Cabin Pressurization, Cabin Air Revitalization, Water Coolant Loop System, Active Thermal Control System, Supply and Waste Water, Waste Collection System, Waste Water Tank, Airlock Support, Extravehicular Mobility Units , Crew Altitude Protection System, and Radioisotope Thermoelectric Generator Cooling and Gaseous Nitrogen Purge for Payloads. The life-support system on
Momsen lung - Misplaced Pages Continue
3444-599: The air that the staff breathe, and at high altitude, where the partial pressure of oxygen is low, for high altitude mountaineering. In aerospace there are applications in unpressurised aircraft and for high altitude parachute drops, and above the Earth's atmosphere, in space suits for extra-vehicular activity . Similar technology is used in life-support systems in submarines, submersibles, atmospheric diving suits , underwater and surface saturation habitats, spacecraft, and space stations, and in gas reclaim systems used to recover
3526-419: The ambient pressure breathing volume components, usually called the breathing loop in a circulating flow rebreather, and the make-up gas supply and control system. The counterlung is an airtight bag of strong flexible material that holds the volume of the exhaled gas until it is inhaled again. There may be a single counterlung, or one on each side of the scrubber, which allows a more even flow rate of gas through
3608-441: The ambient pressure breathing volume, either continuously, or when the user operates the oxygen addition valve, or via a demand valve in an oxygen rebreather, when the volume of gas in the breathing circuit becomes low and the pressure drops, or in an electronically controlled mixed gas rebreather, after a sensor has detected insufficient oxygen partial pressure, and activates a solenoid valve. Valves are needed to control gas flow in
3690-399: The atmosphere or ice deposits. All space missions to date have used supplied food. Life-support systems could include a plant cultivation system which allows food to be grown within buildings or vessels. This would also regenerate water and oxygen. However, no such system has flown in outer space as yet. Such a system could be designed so that it reuses most (otherwise lost) nutrients. This
3772-519: The bell are through a bell umbilical, made up from a number of hoses and electrical cables twisted together and deployed as a unit. This is extended to the divers through the diver umbilicals. The accommodation life support system maintains the chamber environment within the acceptable range for health and comfort of the occupants. Temperature, humidity, breathing gas quality sanitation systems and equipment function are monitored and controlled. Micro-Ecological Life Support System Alternative ( MELiSSA )
3854-470: The breathing gas is a mixture of oxygen and metabolically inactive diluent gas. These can be divided into semi-closed circuit, where the supply gas is a breathable mixture containing oxygen and inert diluents, usually nitrogen and helium, and which is replenished by adding more of the mixture as the oxygen is used up, sufficient to maintain a breathable partial pressure of oxygen in the loop, and closed circuit rebreathers, where two parallel gas supplies are used:
3936-692: The breathing volume, and gas feed from the storage container. They include: Oxygen sensors may be used to monitor partial pressure of oxygen in mixed gas rebreathers to ensure that it does not fall outside the safe limits, but are generally not used on oxygen rebreathers, as the oxygen content is fixed at 100%, and its partial pressure varies only with the ambient pressure. Re breathers can be primarily categorised as diving rebreathers, intended for hyperbaric use, and other rebreathers used at pressures from slightly more than normal atmospheric pressure at sea level to significantly lower ambient pressure at high altitudes and in space. Diving rebreathers must often deal with
4018-406: The capacity of the scrubber to remove carbon dioxide at the rate it is produced by the user. These variables are closely linked, as the carbon dioxide is a product of metabolic oxygen consumption , though not the only product. This is independent of depth, except for work of breathing increase due to gas density increase. There are two basic arrangements controlling the flow of breathing gas inside
4100-401: The carbon dioxide absorbent: 4KO 2 + 2CO 2 = 2K 2 CO 3 + 3O 2 . A small volume oxygen cylinder is needed to fill and purge the loop at the start of use. This technology may be applied to both oxygen and mixed gas rebreathers, and can be used for diving and other applications. Potassium superoxide reacts vigorously with liquid water, releasing considerable heat and oxygen, and causing
4182-416: The complications of avoiding hyperbaric oxygen toxicity, while normobaric and hypobaric applications can use the relatively trivially simple oxygen rebreather technology, where there is no requirement to monitor oxygen partial pressure during use providing the ambient pressure is sufficient. Rebreathers can also be subdivided by functional principle as closed circuit and semi-closed circuit rebreathers. This
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#17329011517054264-442: The correct body temperature, an acceptable pressure on the body and deal with the body's waste products. Shielding against harmful external influences such as radiation and micro-meteorites may also be necessary. Components of the life-support system are life-critical , and are designed and constructed using safety engineering techniques. In underwater diving , the breathing apparatus is considered to be life support equipment, and
4346-468: The diluent, to provide the bulk of the gas, and which is recycled, and oxygen, which is metabolically expended. Carbon dioxide is considered a waste product, and in a correctly functioning rebreather, is effectively removed when the gas passes through the scrubber. There have been a few rebreather designs (e.g. the Oxylite) which use potassium superoxide , which gives off oxygen as it absorbs carbon dioxide, as
4428-439: The diver continues to inhale. Oxygen can also be added manually by a button which activates the demand valve. Some simple oxygen rebreathers had no automatic supply system, but only the manual feed valve, and the diver had to operate the valve at intervals to refill the breathing bag as the volume of oxygen decreased below a comfortable level. All rebreathers other than oxygen rebreathers may be considered mixed gas rebreathers, as
4510-504: The effects of Coriolis force (a force imparted at right angles to motion within the cabin) must be dealt with. And there is concern that rotation could aggravate the effects of vestibular disruption. American Mercury, Gemini and Apollo spacecraft contained 100% oxygen atmospheres, suitable for short duration missions, to minimize weight and complexity. The Space Shuttle was the first American spacecraft to have an Earth-like atmospheric mixture, comprising 22% oxygen and 78% nitrogen. For
4592-501: The environmental control and life-support system (ECLSS)" for Sundancer has begun. Natural LSS like the Biosphere 2 in Arizona have been tested for future space travel or colonization. These systems are also known as closed ecological systems . They have the advantage of using solar energy as primary energy only and being independent from logistical support with fuel. Natural systems have
4674-474: The forward escape trunk : five were picked up by the Japanese; three more reached the surface "but were unable to hang on or breathe and floated off and drowned"; the fate of the other five is unknown. Not all the escapees from the trunk used the Momsen lung. An officer had his mouthpiece knocked out shortly after leaving the submarine. One of the trunk ascents was made without a Momsen lung. Many were unable to leave
4756-421: The function of the equipment. In human spaceflight , a life-support system is a group of devices that allow a human being to survive in outer space. US government space agency NASA , and private spaceflight companies use the phrase "environmental control and life-support system" or the acronym ECLSS when describing these systems. The life-support system may supply air, water and food. It must also maintain
4838-410: The gas composition other than removing the carbon dioxide. In some rebreathers the oxygen cylinder has oxygen supply mechanisms in parallel. One is constant flow ; the other is a manual on-off valve called a bypass valve; both feed into the same hose which feeds the counterlung. Others are supplied via a demand valve on the counterlung. This will add gas at any time that the counterlung is emptied and
4920-435: The granules by size, or by moulding granules at a consistent size and shape. Gas flow through the scrubber may be in one direction in a loop rebreather, or both ways in a pendulum rebreather. The scrubber canister generally has an inlet on one side and an outlet on the other side. A typical absorbent is soda lime , which is made up of calcium hydroxide Ca(OH) 2 , and sodium hydroxide NaOH. The main component of soda lime
5002-486: The highest degree of efficiency due to integration of multiple functions. They also provide the proper ambience for humans which is necessary for a longer stay in outer space. Underwater habitats and surface saturation accommodation facilities provide life-support for their occupants over periods of days to weeks. The occupants are constrained from immediate return to surface atmospheric pressure by decompression obligations of up to several weeks. The life support system of
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#17329011517055084-475: The inspired volume at normal atmospheric pressure , or about 20% of the available oxygen in the air at sea level . Exhaled air at sea level contains roughly 13.5% to 16% oxygen. The situation is even more wasteful of oxygen when the oxygen fraction of the breathing gas is higher, and in underwater diving, the compression of breathing gas due to depth makes the recirculation of exhaled gas even more desirable, as an even larger proportion of open circuit gas
5166-401: The intermediate reaction, the carbonic acid reacts exothermically with sodium hydroxide to form sodium carbonate and water: H 2 CO 3 + 2NaOH –> Na 2 CO 3 + 2H 2 O + heat. In the final reaction, the sodium carbonate reacts with the slaked lime (calcium hydroxide) to form calcium carbonate and sodium hydroxide: Na 2 CO 3 + Ca(OH) 2 –> CaCO 3 + 2NaOH. The sodium hydroxide
5248-435: The internal pressure is maintained at one atmosphere, there is no risk of acute oxygen toxicity. This is an underwater diving application, but has more in common with industrial applications than with ambient pressure scuba rebreathers. Different design criteria apply to SCBA rebreathers for use only out of the water: Mountaineering rebreathers provide oxygen at a higher concentration than available from atmospheric air in
5330-534: The large volumes of helium used in saturation diving . The recycling of breathing gas comes at the cost of technological complexity and specific hazards, some of which depend on the application and type of rebreather used. Mass and bulk may be greater or less than open circuit depending on circumstances. Electronically controlled diving rebreathers may automatically maintain a partial pressure of oxygen between programmable upper and lower limits, or set points, and be integrated with decompression computers to monitor
5412-416: The length of the mission, astronauts may need artificial gravity to reduce the effects of space adaptation syndrome , body fluid redistribution, and loss of bone and muscle mass. Two methods of generating artificial weight in outer space exist. If a spacecraft's engines could produce thrust continuously on the outbound trip with a thrust level equal to the mass of the ship, it would continuously accelerate at
5494-516: The lungs, which could cause them to rupture. This has since been found to be higher risk than a constant relaxed exhalation during ascent. Walter F. Schlech, Jr. and others examined submerged escape without breathing devices and discovered that ascent was possible from as deep as 300 ft (91 m). One writer suggested that "the Momsen Lung concept may have killed far more submariners than it rescued". Rebreather#Counterlungs A rebreather
5576-413: The more immediate effect that the metabolic parameters have. Outer space life-support systems maintain atmospheres composed, at a minimum, of oxygen, water vapor and carbon dioxide. The partial pressure of each component gas adds to the overall barometric pressure . However, the elimination of diluent gases substantially increases fire risks, especially in ground operations when for structural reasons
5658-448: The occupants free access to the ambient environment within a specific depth range, while saturation divers accommodated in surface systems are transferred under pressure to the working depth in a closed diving bell The life support system for the bell provides and monitors the main supply of breathing gas , and the control station monitors the deployment and communications with the divers. Primary gas supply, power and communications to
5740-400: The personnel under pressure in the accommodation chambers and closed diving bell. It includes the following components: The life support system for the bell provides and monitors the main supply of breathing gas, and the control station monitors the deployment and communications with the divers. Primary gas supply, power and communications to the bell are through a bell umbilical, made up from
5822-402: The photo, benefit from easier field repair if a tear or hole while helical corrugations allow efficient drainage after cleaning. Breathing hoses are usually long enough to connect the apparatus to the user's head in all attitudes of their head, but should not be unnecessarily long, which will cause additional weight, hydrodynamic drag , risk snagging on things, or contain excess dead space in
5904-429: The rate of 32.2 feet per second (9.8 m/s) per second, and the crew would experience a pull toward the ship's aft bulkhead at normal Earth gravity (one g). The effect is proportional to the rate of acceleration. When the ship reaches the halfway point, it would turn around and produce thrust in the retrograde direction to slow down. Alternatively, if the ship's cabin is designed with a large cylindrical wall, or with
5986-418: The rebreather, known as the pendulum and loop systems. In the pendulum configuration, the user inhales gas from the counterlung through a breathing hose, and exhaled gas returns to the counterlung by flowing back through the same hose. The scrubber is usually between the breathing hose and the counterlung bag, and gas flow is bi-directional. All of the flow passages between the user and the active absorbent in
6068-467: The scrubber are dead space – volume containing gas which is rebreathed without modification by the rebreather. The dead space increases as the absorbent is depleted. Breathing hose volume must be minimised to limit dead space. In the loop configuration, the user inhales gas through one hose, and exhales through a second hose. Exhaled gas flows into the scrubber from one side, and exits at the other side. There may be one large counterlung, on either side of
6150-621: The scrubber contents from freezing, and helps reduce heat loss from the user. Both chemical and compressed gas oxygen have been used in experimental closed-circuit oxygen systems – the first on Mount Everest in 1938 . The 1953 expedition used closed-circuit oxygen equipment developed by Tom Bourdillon and his father for the first assault team of Bourdillon and Evans ; with one "dural" 800l compressed oxygen cylinder and soda lime canister (the second (successful) assault team of Hillary and Tenzing used open-circuit equipment). Similar requirement and working environment to mountaineering, but weight
6232-463: The scrubber, or two smaller counterlungs, one on each side of the scrubber. Flow is in one direction, enforced by non-return valves, which are usually in the breathing hoses where they join the mouthpiece. Only the flow passage in the mouthpiece before the split between inhalation and exhalation hoses is dead space, and this is not affected by hose volume. There are some components that are common to almost all personal portable rebreathers. These include
6314-436: The scrubber, which can reduce work of breathing and improve scrubber efficiency by a more consistent dwell time . The scrubber is a container filled with carbon dioxide absorbent material, mostly strong bases , through which the exhaled gas passes to remove the carbon dioxide. The absorbent may be granular or in the form of a moulded cartridge. Granular absorbent may be manufactured by breaking up lumps of lime and sorting
6396-442: The service, they may be made of a flexible polymer, an elastomer , a fibre or cloth reinforced elastomer, or elastomer covered with a woven fabric for reinforcement or abrasion resistance. If the woven layer is bonded to the outside surface it protects the rubber from damage from scrapes but makes it more difficult to wash off contaminants. Breathing hoses typically come in two types of corrugation. Annular corrugations, as depicted in
6478-433: The total cabin pressure must exceed the external atmospheric pressure; see Apollo 1 . Furthermore, oxygen toxicity becomes a factor at high oxygen concentrations. For this reason, most modern crewed spacecraft use conventional air (nitrogen/oxygen) atmospheres and use pure oxygen only in pressure suits during extravehicular activity where acceptable suit flexibility mandates the lowest inflation pressure possible. Water
6560-505: The trunk or discouraged from attempting an escape. Most of the crew perished. The Momsen lung was replaced by the Steinke hood beginning in 1962. German submarines had such a escape breathing apparatus as standard equipment since 1912. The British Royal Navy used the similar Davis Submerged Escape Apparatus since 1927. They adopted the practice of " blow and go " in which the sailor would exhale before ascent to avoid air over-expanding
6642-416: The type include: A cryogenic rebreather removes the carbon dioxide by freezing it out in a "snow box" by the low temperature produced as liquid oxygen evaporates to replace the oxygen used. This may be compared with some applications of open-circuit breathing apparatus: The widest variety of rebreather types is used in diving, as the consequences of breathing under pressure complicate the requirements, and
6724-425: The water of the soda lime and formed carbonic acid, changing the pH from basic to acid, as the change of colour shows that the absorbent has reached saturation with carbon dioxide and must be changed. The carbon dioxide combines with water or water vapor to produce a weak carbonic acid: CO 2 + H 2 O –> H 2 CO 3 . This reacts with the hydroxides to produce carbonates and water in an exothermic reaction. In
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