Pages in category "Space suit components"

The following 7 pages are in this category, out of 7 total. This list may not reflect recent changes (learn more).

C

Carbon dioxide scrubber

H

Hard Upper Torso

L

Liquid Cooling and Ventilation Garment

M

Maximum Absorbency Garment

P

Primary Life Support System

S

Suitport

Carbon dioxide scrubberA carbon dioxide scrubber is a device which absorbs carbon dioxide (CO2). It is used to treat exhaust gases from industrial plants or from exhaled air in life support systems such as rebreathers or in spacecraft, submersible craft or airtight chambers. Carbon dioxide scrubbers are also used in controlled atmosphere (CA) storage.

Contents

1 Methods o 1.1 Regenerative carbon dioxide removal system

o 1.2 Activated carbon

2 Strong bases

Methods

Methods of carbon dioxide scrubbing include :

Adsorption [1] Amine absorption

Calcium oxide : Carbon dioxide reacts with quicklime (calcium oxide), to form limestone (calcium carbonate).[2]

Serpentinite : The metamorphic mineral serpentinite (magnesium silicate hydroxide), is composed of magnesium, silicon and oxygen.

Regenerative carbon dioxide removal system (RCRS)

Algae based carbon sink

Olivine:[3][4]

Molecular sieve

Polymer membrane gas separators [5] [6]

Activated carbon

Reversing heat exchangers

Monoethanolamine solutions absorb carbon dioxide when cold, and release it when warmed.

Regenerative carbon dioxide removal system

The regenerative carbon dioxide removal system (RCRS) on the space shuttle orbiter uses a two-bed system that provides continuous removal of carbon dioxide without expendable products. Regenerable systems allow a shuttle mission a longer stay in space without having to replenish its sorbent canisters. Older lithium hydroxide (LiOH)-based systems, which are non-regenerable, are being replaced by regenerable metal-oxide-based systems. A system based on metal oxide primarily consists of a metal oxide sorbent canister and a regenerator assembly. It works by removing carbon dioxide using a sorbent material and then regenerating the sorbent material. The metal-oxide sorbent is regenerated by pumping air heated to around 400 °F at 7.5 scfm through its canister for 10 hours.[7]

Activated carbon

Activated carbon can be used as a carbon dioxide scrubber. Air with high carbon dioxide content, such as air from fruit storage locations, can be blown through beds of activated carbon and the carbon dioxide will adsorb onto the activated carbon. Once the bed is saturated it must then be "regenerated" by blowing low carbon dioxide air, such as ambient air, through the bed. This will release the carbon dioxide from the bed, and it can then be used to scrub again, leaving the net amount of carbon dioxide in the air the same as when you started.

Strong bases

Various strong bases such as soda lime, sodium hydroxide, potassium hydroxide, and lithium hydroxide are able to remove carbon dioxide by chemically reacting with it. In particular, lithium hydroxide is used aboard space craft to remove carbon dioxide from the atmosphere. It reacts with carbon dioxide to make lithium carbonate:[8]

2 LiOH(s) + 2 H2O(g) → 2 LiOH.H2O(s)

2 LiOH.H2O(s) + CO2(g) → Li2CO3(s) + 3 H2O(g)

The net reaction being:

2 LiOH(s) + CO2(g) → Li2CO3(s) + H2O(g)

Hard Upper Torso

A Hard Upper Torso Assembly, or HUT, is a central component of many space suits, notably NASA's Extravehicular Mobility Unit (EMU). The fiberglass HUT forms a rigid enclosure about the upper body of the occupant, providing pressure containment for this part of the body. The HUT incorporates structural attachment points for the arms, Lower Torso Assembly (LTA), helmet, chest-mounted Display and Controls Module (DCM), and Primary Life Support Subsystem (PLSS) backpack.[1]

The original HUT design for the EMU, first used in 1980, included bellowed shoulder bearings, which allowed for variation in the angle of the shoulder bearings. This allowed for one configuration to ease donning of the suit, and a different configuration to allow maximum mobility during EVA. However, the limited life of the bellows prompted a redesign in 1990 to a fixed shoulder bearing angle and position, referred to as the Planar HUT, resulting in reduced mobility and more difficult donning and doffing.[2]

Because of the high cost of manufacturing, only three sizes of HUTs are produced for the EMU. This has the effect of limiting the number of people who can be properly fit for the suit.[2] The three HUT sizes are supposed to accommodate occupants from the 5th to the 95th percentile.[3]

The HUT also includes an In-Suit Drink Bag, with a plastic tube extending into the helmet, to allow the astronaut to stay hydrated.

Liquid Cooling and Ventilation Garment

An astronaut wearing a Liquid Cooling and Ventilation Garment

A Liquid Cooling and Ventilation Garment, or LCVG, is a form-fitting garment worn by astronauts in order to maintain a comfortable core body temperature during extra-vehicular activity. The LCVG accomplishes this task by circulating cool water through a network of flexible tubes in direct contact with the astronaut's skin. The water draws heat away from the body, resulting in a lower core temperature. The water then returns to the Primary Life Support System, or PLSS, where it is cooled in a heat exchanger before being recirculated. In an independent space suit, the heat is ultimately transferred to a thin sheet of ice (formed by a separate feed water source). Due to the extremely low pressure in space, the heated ice sublimates directly to water vapor, which is then vented away from the suit. In a dependent space suit (such as the ones used in the Gemini program or within lunar orbit on the Apollo program), the heat is carried back to a host spacecraft through an umbilical connection, where it is ultimately radiated or sublimated via the spacecraft's own thermal control system.

Because the space environment is essentially a vacuum, heat cannot be lost through heat convection, and can only be directly dissipated through thermal radiation, a much slower process. Thus, even though the environment of space can be extremely cold, excessive heat build-up is inevitable. Without an LCVG, there would be no means by which to expel this heat, and it would affect not only EVA performance, but the health of the suit occupant as well. The LCVG used with the Apollo/Skylab A7L suit could remove heat at a rate of approximately 2000 Btu/h (600 watts).[1]

The LCVG used with NASA's Extravehicular Mobility Unit is primarily constructed of spandex, with a nylon tricot liner.[2] The tubes are polyvinyl chloride.

A Liquid Cooling and Ventilation Garment is differentiated from a Liquid Cooling Garment by the presence of ventilation ducts, which draw exhaled gas from the suit's extremities and return it to the Primary Life Support System.

Maximum Absorbency Garment

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Drawing of a Maximum Absorbency Garment

A Maximum Absorbency Garment (MAG) is a piece of clothing astronauts wear during liftoff, landing, and extra-vehicular activities to absorb urine and feces. Usually, astronauts urinate into the MAG, and wait to defecate when they return to the spacecraft. The adult-sized diaper with extra absorption material is used because astronauts cannot remove their space suits during long operations. Three MAGs are given during space shuttle missions, one each for during launch, reentry, and a spare in case reentry needs to be tried again. It is worn underneath the Liquid Cooling and Ventilation Garment (LCVG).

The MAGs are similar to adult diapers but are modified so that they are pulled up like shorts. A powdery chemical absorbent called sodium polyacrylate is incorporated into the fabric of the garment. Sodium polyacrylate can absorb around four hundred times its weight in water. The MAG absorbs the liquid and pulls it away from the skin.

In 1988, the Maximum Absorbency Garment replaced the Disposable Absorption Containment Trunk (DACT) for female astronauts. Male astronauts then followed suit, because it did not leak and it was more comfortable. In the 1980s, NASA ordered 3,200 of the diapers and, as of 2007, a third of the supply remains.

Primary Life Support System

The PLSS from the Apollo A7L suit, with its outer cover removed

Diagram of the A7L PLSS

A Primary (also Portable or Personal) Life Support System/Subsystem, or PLSS, is the "backpack" of a spacesuit. It provides most of the functions of a spacecraft life support system, in a smaller package. The functions performed by the PLSS include:

regulating suit pressure providing breathable oxygen

removing carbon dioxide, humidity, odors, and contaminants from breathing oxygen

cooling and recirculating oxygen and water through the Liquid Cooling and Ventilation Garment, or LCVG.

sensing and reporting suit parameters

providing communications for the suit occupant

The air handling function of a PLSS is similar to that of a diving rebreather, in that exhaled gases are recycled into the breathing gas in a closed loop.

Contents

1 Apollo OPS 2 Space Shuttle/International Space Station PLSS

3 Developing technologies

Apollo OPS

The breathing set used in the Apollo lunar landing missions had an emergency bailout in case the main supply failed. This bailout was provided by an oxygen purge system (OPS) similar to an open-circuit scuba system. Like the PLSS, the OPS also maintained suit pressure and removed heat and water vapor. When activated, the OPS provided oxygen to a separate inlet on the pressure suit. A vent valve on a separate suit outlet was manually opened to establish a steady, once-through flow to space, removing CO2, heat and water vapor. Like scuba, the OPS used gas far less efficiently than the PLSS, but as an emergency backup simplicity and reliability were paramount. The OPS was a separate unit mounted on top of the PLSS backpack, immediately behind the astronaut's helmet. The OPS was also used as a backup on tethered EVAs where a spacecraft provided oxygen to the astronaut through an umbilical cable.

Similar systems are now used by Space Shuttle and International Space Station astronauts.

Space Shuttle/International Space Station PLSS

The PLSS for the EMU suit currently used on the Space Shuttle and International Space Station is manufactured by Hamilton Sundstrand. It is mounted to the back of the Hard Upper Torso (HUT) assembly.

Oxygen (O2), carbon dioxide (CO2) and water vapor are drawn from the extremities of the suit by the LCVG, which sends the gas to the PLSS. When gas enters the PLSS, activated charcoal removes odors and lithium hydroxide (LiOH) removes carbon dioxide. Next, the gas passes through a fan which maintains a flow rate of about six cubic feet per minute. A sublimator then condenses water vapor, which is removed by a "slurper" and a rotary separator. The removed water is stored and used to supplement the water supply used in the LCVG. The sublimator also cools the remaining oxygen to about 55 °F (~12.8 °C). A flow sensor monitors the flow rate.

Extra oxygen is added to the flow from a storage tank as necessary, downstream of the flow sensor. The oxygen is then returned to the suit at the back of the head, where it flows down over the astronaut's face. By delivering oxygen to the helmet and drawing gas from the extremities, the suit is designed to ensure that the suit occupant breathes the freshest oxygen possible.

The operating pressure of the suit is maintained at 4.3 psi during extravehicular operations, and 0.7 psi relative to external pressure while in intravehicular mode, i.e., before and after extra-vehicular activity (EVA).

Developing technologies

Technologies being considered for application in future PLSSs include Pressure Swing Adsorption (PSA), a process by which CO2 can be separated from gas more efficiently, and through a repeatable process, as opposed to the current LiOH canisters, which become saturated with each use, and are limited to around 8 hours.[1] By regenenerating the sorbent during EVA, the size and weight of the sorbent canister can greatly reduced. PSA accomplishes this by venting CO2 and water vapor into space.[2]

Apollo/Skylab A7L

Apollo 11 A7L space suit worn by Buzz Aldrin

The A7L Apollo & Skylab spacesuit is the primary pressure suit worn by NASA astronauts for Project Apollo, the three manned Skylab flights, and the Apollo-Soyuz Test Project between 1968 and the termination of the Apollo program in 1975. The "A7L" designation is used by NASA as the seventh Apollo spacesuit designed and built by ILC Dover, a pressure suit manufacturer located south of Dover, Delaware. The A7L is a design evolution of ILC's A5L and A6L. The A5L was the initial design. The A6L introduced the integrated thermal and micrometeroid cover layer. After the Apollo 1 fire, the suit was upgraded to be fire proof and given the designation A7L.[1][2]

Contents

1 Basic design o 1.1 Extravehicular Pressure Garment Assembly

1.1.1 Torso Limb Suit Assembly

1.1.2 Integrated Thermal Micrometeroid Garment

1.1.3 Liquid Cooling Garment

o 1.2 Intravehicular (CMP) Pressure Garment Assembly

1.2.1 Torso Limb Suit Assembly

1.2.2 Intravehicular Cover Layer

1.2.3 Constant Wear Garment

2 A7LB Spacesuit (Apollo & Skylab)

3 A7LB Suit (Apollo-Soyuz Test Project)

4 References

5 External links

Basic design

Apollo 11 A7L space suit worn by Neil Armstrong

The basic design of the A7L suit was a one piece, five-layer "torso-limb" suit with convoluted joints made of synthetic rubber at the shoulders, elbows, wrist, hips, ankle, and knee joints, "link-net" meshing to prevent the suit from ballooning at the joints, and a shoulder "cable block" assembly to allow the shoulder to be extended and retracted by its wearer. Metal rings at the neck and forearms allowed for the connection of the pressure gloves and the famous Apollo "fishbowl helmet" (adopted by NASA as it allowed an unrestricted view, as well as eliminating the need for a visor seal required in the Mercury and Gemini & Apollo "Block I" spacesuit helmets). A "cover layer," which was designed to be fireproof after the Apollo 1 launchpad fire, was attached to the pressure garment assembly and was removable for repairs and inspection. All A7L suits featured a vertical zipper that went from the shoulder assembly of the suit down to the crotch for entering and exiting the suit.

Extravehicular Pressure Garment Assembly

Torso Limb Suit Assembly

Between Apollos 7 and 14, the two lunar module astronauts, the Commander (CDR) and Lunar Module pilot (LMP), had Torso Limb Suit Assemblies (TSLA) with six life support connections placed in two parallel columns on the chest. The 4 lower connectors passed oxygen, an electrical headset/biomed connector was on the upper right, and a bidirectional cooling water connector was on the upper left.

Integrated Thermal Micrometeroid Garment

Covering the Torso Limb Suit Assembly was an Integrated Thermal Micrometeroid Garment (ITMG). This garment protected the suit from abrasion and protected the astronaut from thermal solar radiation and micrometeoroids which could puncture the suit. The garment was made from thirteen layers of material which were (from inside to outside):rubber coated nylon, 5 layers of aluminized Mylar, 4 layers of nonwoven Dacron, 2 layers of aluminized Kapton film/Beta marquisette laminate, and Teflon coated Beta filament cloth.

Additionally, the ITMG also used a patch of "Chromel-R" woven steel (the familiar silver-colored patch seen especially on the suits worn by the Apollo 11 crew) for abrasion protection from the Portable Life Support System (PLSS) backpack. Chromel-R was also used on the uppers of the lunar boots and on the EVA gloves. Finally, patches of Teflon were used for additional abrasion protection on the knees waist and shoulders of the ITMG.

Starting with Apollo 13, a red band of Beta cloth was incorporated the commander's ITMG on each arm and leg, as well as a red stripe on the newly added EVA central visor assembly to easily distinguish the commander from the lunar module pilot on the lunar surface. The stripes, initially known as "Public Affairs stripes" but quickly renamed Commanders Stripes, were added by Brian Duff, head of Public Affairs at the Marshall Space Flight Center to resolve the problem for the media as well as NASA of identifying astronauts in photographs. [3]

Liquid Cooling Garment

Lunar crews also wore a three-layer Liquid Cooling and Ventilation Garment (LCG) or "union suit" with plastic tubing which circulated water to cool the astronaut down, minimizing sweating and fogging of the suit helmet. Water was supplied to the LCG from the PLSS backpack, where the circulating water was chilled by an ice sublimator.

Intravehicular (CMP) Pressure Garment Assembly

Torso Limb Suit Assembly

The Command Module pilot (CMP) had a TSLA similar to the commander and lunar module pilot, but with unnecessary hardware deleted since the CMP would not be performing any extravehicular activities. For example, the CMP's TSLA only one set of gas connectors instead of two, and had no water cooling connector. Also deleted was the pressure relief valve in the sleeve of the suit and the tether mounting attachments which were used in the lunar module. The TSLA for the CMP also deleted an arm bearing that allowed the arm to rotate above the elbow.

Intravehicular Cover Layer

Command module pilots only wore a three-layer Intravehicular Cover Layer (IVCL) of nomex and beta cloth for fire and abrasion protection.

Constant Wear Garment

The CMP wore a simpler cotton fabric union suit called the Constant Wear Garment (CWG) underneath the TSLA instead of the water cooled Liquid Cooling Garment. His cooling came directly from the flow of oxygen into his suit via an umbilical from the spacecraft environmental control system. When not performing lunar EVA's, the LMP and CDR also wore a CWG instead of the LCG.

A7LB Spacesuit (Apollo & Skylab)

For the last three Apollo lunar flights Apollos 15, 16, and 17, the CDR and LMP started wearing a new moonwalking suit designed for longer duration J-series missions, in which three EVAs would be conducted and the lunar rover (LRV) would be used for the first time. Originally developed by ILC-Dover as the "A9L," but given the designation "A7LB" by NASA[4], the new suit incorporated two new joints at the neck and waist. The waist joint was added to allow the astronaut to sit on the LRV and the neck joint was to provide additional visibility while driving the LRV. Because of the waist joint, the six life-support connecters were rearranged from the parallel pattern to a set of two "triangles," and the up-and-down zipper was relocated to the left front side of the suit, going around the back, and terminating on the right shoulder.[2]

In addition, the EVA backpacks were modified to carry more oxygen, lithium hydroxide (LiOH), more power, and cooling water for the longer EVAs. [2] To facilitate these longer EVAs, small energy bars were carried in special pouches beneath the interior of the suit helmet ring, and the astronauts wore collar-like drinking water bags beneath the outer suit.

Because the J-series CSMs incorporated the Scientific Instrument Module (SIM) Bay, which used special film cameras similar to those used on Air Force spy satellites, and required a "deep space" EVA for retrieval, the CMP for each of the three J-series missions wore a five-connector A7LB based H-series A7L suits, with the liquid cooling connections eliminated as the CMP would be attached to a life-support umbilical (like that used on Gemini EVAs) and only an "oxygen purge system" (OPS) would be used, along with a "red apple" lanyard, for emergency backup in the case of the failure of the umbilical. The CMP wore the commander's red-striped EVA visor assembly, while the LMP, who performed a "stand-up EVA" (to prevent the umbilical from getting "fouled up" and to store the film into the CSM) in the spacecraft hatch and connected to his normal life-support connections, wore the plain white EVA visor assembly.

For the three manned Skylab missions, all three astronauts wore a slightly modified A7LB suit for launch, docking, undocking, and EVA. The suit had a simplified and less expensive Integrated Thermal and Micrometeroid Garment (ITMG), and a simpler and less expensive extravehicular visor assembly.[5]

With the exception of the Orbital Workshop (OWS) repairs carried out by Skylab 2 and Skylab 3, all of the Skylab EVAs were conducted in connection to the routine maintenance carried out on the Apollo Telescope Mount, which housed the station's solar telescopes. Because of the short duration of those EVAs, and as a need to protect the delicate instruments, the Apollo lunar EVA backpack was replaced with a Gemini-style umbilical assembly, except that it was modified to incorporated both breathing air (Skylab's atmosphere was 80% oxygen and 20% nitrogen at 5 psi) and liquid water for cooling. The assembly was worn on the astronaut's waist and served as the interface between the umbilical and the suit. An emergency oxygen pack was strapped to the wearer's right thigh and is able to supply a 30 minute emergency supply of pure oxygen in the case of umbilical failure. An EVA visor assembly similar to that used today on the Shuttle/ISS Extravehicular Mobility Unit was worn over the pressure helmet, but Apollo EVA gloves were used.

A7LB Suit (Apollo-Soyuz Test Project)

Deke Slayton wearing the ASTP Suit - Note there's only three connectors

For the Apollo-Soyuz Test Project, NASA decided to use the A7LB CMP pressure suit assembly worn on the J-missions with a few changes to save cost and weight since an EVA was not planned during the mission. The changes included a simplified cover layer which was cheaper, lighter and more durable as well as the removal of the pressure relief valve and unused gas connectors. No EVA visor assemblies or EVA gloves were carried on the mission.[6]

As a note, the ASTP A7LB suit was the only Apollo suit to use the "worm" logo, a logo that became familiar with all of NASA's pressure, space, and flight suits and all Space Shuttle orbiters between 1981 and 2000.

References

1. ̂ "SP-4011:Skylab A Chronology". NASA. 1977. http://history.nasa.gov/SP-4011/part2c.htm. Retrieved 2007-07-07.

2. ^ a b c Lutz, Charles; Harley L. Stutesman, Maurice A. Carson, and James W. McBarron II (1975). "EMU Development". Development of the Extravehicular Mobility Unit - pages 22-26. NASA. http://www.hq.nasa.gov/alsj/tnD8093EMUDevelop.html. Retrieved 2007-07-08.

3. ̂ "Commander's Stripes". Apollo Lunar Surface Journal. NASA. http://history.nasa.gov/alsj/alsj-CDRStripes.html.

4. ̂ Harold J. McMann; Thomas, Kenneth P.. US Spacesuits (Springer Praxis Books / Space Exploration). Praxis. p. 140. ISBN 0-387-27919-9.

5. ̂ "Space Suite Evolution" (PDF). Space Suit Evolution - page 22. NASA. 1975. http://history.nasa.gov/spacesuits.pdf. Retrieved 2007-07-09.

6. ̂ "Apollo ASTP Press Kit" (PDF). Apollo ASTP Press Kit pages 52-53. NASA. 1975. http://history.nasa.gov/astp/astp%20press%20kit%20(us).pdf. Retrieved 2007-07-07.

Suitport

A NASA lunar rover concept, incorporating a pair of suitports

Diagram of a suitport system

A suitport or suitlock is a proposed alternative to an airlock, designed for use in hazardous environments and in human spaceflight, especially planetary surface exploration.

Contents

1 Operation 2 Advantages

3 Development and use

4 See also

5 References

Operation

In a suitport system, a rear-entry space suit is attached and sealed against the outside of a spacecraft, space habitat, or rover. To go on an extra-vehicular activity (EVA), an astronaut first enters the suit from inside the vehicle, and closes and seals the space suit backpack and the vehicle's hatch (which seals to the backpack for dust containment). The astronaut then unseals and separates the suit from the vehicle, and is ready to perform an EVA.[1][2][3]

To re-enter the vehicle, the astronaut backs up to the suitport and seals the suit to the vehicle, before opening the hatch and backpack and transferring back into the vehicle. If the vehicle and suit do not operate at the same pressure, it will be necessary to equalize the two pressures before the hatch can be opened.

Advantages

Suitports carry two major advantages over traditional airlocks. First, the mass and volume required for a suitport would be significantly less than that required for an airlock. Launch mass is at a premium in modern chemical rocket-powered launch vehicles, at an estimated cost of US$60,000 per kilogram delivered to the lunar surface.[4]

Secondly, suitports can eliminate or minimize the problem of dust mitigation. During the Apollo program, it was discovered that the lunar soil is electrically charged, and adheres readily to any surface with which it comes into contact, a problem magnified by the sharp, barb-like shapes of the dust particles.[5] Lunar dust may be harmful in several ways:

The abrasive nature of the dust particles may rub and wear down surfaces through friction.

The dust may have a negative effect on coatings used on gaskets to seal equipment from space, optical lenses that include solar panels and windows as well as wiring.

The dust may cause damage to an astronaut's lungs, nervous, and cardiovascular systems, leading to conditions such as pneumoconiosis.[6][7]

During the Apollo missions, the astronauts donned their space suits inside the Apollo Lunar Module cabin, which was then depressurized to allow them to exit the vehicle. Upon the end of EVA, the astronauts would re-enter the cabin in their suits, bringing with them a great deal of dust which had adhered to the suits. Several astronauts reported a "gunpowder" smell and respiratory or eye irritation upon opening their helmets and being exposed to the dust.[5]

With a suitport, dust or other environmental contaminants cannot enter the cabin of the vehicle.[1] When the suit is attached to the vehicle, any dust which may have adhered to the backpack of the suit is sealed between the outside of the backpack and the vehicle-side hatch. Any dust on the suit that is not on the backpack remains sealed outside the vehicle. Likewise, the suitport prevents contamination of the external environment by microbes carried by the astronaut.

Development and use

As of 1995, suitports have found a practical, terrestrial application as part of a NASA Ames hazardous materials vehicle, where the use of the suitport eliminates the need to decontaminate the hazmat suit before doffing.[8] A suitport prototype built by Brand Griffin has been used in a simulated lunar gravity test on board NASA Johnson's C-135 aircraft.[8]

Patents for suitport designs were filed in 1996 by Philip Culbertson Jr. of NASA's Ames Research Center,[1] and in 2003 by Joerg Boettcher, Stephen Ransom, and Frank Steinsiek.[2]

Suitports may find use as part of future NASA projects aimed at achieving the Vision for Space Exploration, which calls for a return to the Moon by the year 2020, and eventual manned exploration of Mars.

What is an airlock?

Airlock

A glovebox for handling air-sensitive substances. Two airlocks (one small and one large) are attached to the right for moving samples in and out without disturbing the atmosphere inside.

An airlock is a device which permits the passage of people and objects between a pressure vessel and its surroundings while minimizing the change of pressure in the vessel and loss of air from it. The lock consists of a small chamber with two airtight doors in series which do not open simultaneously.

An airlock may be used for passage between environments of different gases rather than different pressures, to minimize or prevent the gases from mixing.

An airlock may also be used underwater to allow passage between an air environment in a pressure vessel and a water environment outside, in which case the airlock can contain air or water. This is called a floodable airlock or an underwater airlock, and is used to prevent water from entering a submersible vessel or an underwater habitat.

Contents

1 Use 2 Applications

3 Similar mechanisms

4 Fictional airlocks

5 See also

Use

Before opening either door, the air pressure of the airlock—the space between the doors—is equalized with that of the environment beyond the next door to open. This is analogous to a waterway lock: a section of waterway with two watertight gates, in which the water level is varied to match the water level on either side.

A gradual pressure transition minimizes air temperature fluctuations (see Boyle's law), which helps reduce fogging and condensation, decreases stresses on air seals and allows safe verification of pressure suit and space suit operation.

Where a person who is not in a pressure suit moves between environments of greatly different pressures, an airlock changes the pressure slowly to help with internal air cavity equalization and to prevent decompression sickness. This is critical in scuba diving, and a diver may have to wait in an airlock for some hours in line with decompression tables.

Applications

Airlocks are used in

aviation , certain airplanes are equipped with airlocks for skydiving, and/or emergency exits.

spacecraft and spacestations , to maintain the habitable environment when persons are exiting or entering the craft.

hyperbaric chambers , to allow entry and exit while maintaining the pressure difference with the surroundings.

submarines , diving chambers, and underwater habitats to permit divers to exit and enter.

torpedo tubes and escape trunks in submarines are airlocks.

cleanrooms , protected environments in which dust, dirt particles, and other contaminants are excluded partially by maintaining the room at a higher pressure than the surroundings.

hazardous environments, such as nuclear reactors and some biochemical laboratories, in which dust and particles are prevented from leaking out by maintaining the room at a lower pressure than the surroundings.

pressurized domes such as the USF Sun Dome and BC Place Stadium, where pressure loss would cause collapse of the structure.

electron microscopes , where the interior is near vacuum so air does not affect the electron path.

parachute airlocks , where airfoil collapse due to depressurization can result in dangerous loss of altitude.

Similar mechanisms

In cold climates, two doors arranged in an airlock configuration are common in building entrances. While not airtight, the double doors minimize the loss of heated air from the building. A similar arrangement is common in hot climates, where it is used to keep interior spaces cool. Revolving doors may be used for the same purpose.

Some jewelry stores and banks have airlock-like doors to slow the escape of thieves.

Butterfly farms and aviaries usually have an airlock-like entrance to prevent the exit of inhabitants and entrance of predatory species.

Fictional airlocks

A four-door airlock (with, therefore, three interior chambers) was proposed by science fiction writer H. Beam Piper in his novel Uller Uprising. The fictional atmosphere inside the structure was human-breathable, while the outside atmosphere was highly toxic. Only one door of the airlock opened at a time, and the middle chamber of the three would always contain a vacuum to minimize traces of the exterior atmosphere reaching the habitat.

Thermal Micrometeoroid Garment

Cross-section of layers in space suit construction

An (Integrated) Thermal Micrometeoroid Garment (TMG or ITMG) is the outer layer of a space suit. The TMG has three functions: to insulate the suit occupant and prevent heat loss, to shield the occupant from harmful solar radiation, and to protect the astronaut from micrometeoroids and other orbital debris, which could puncture the suit and depressurize it.

The specific design of TMGs varies between different space agencies and different suits, though they all serve the same purpose.

Apollo/Skylab A7L suit

Micrometeoroid impacts in Beta cloth

Outside of a Liquid Cooling and Ventilation Garment, pressure bladder, and restraint layer, the TMG for the A7L suit worn on the Moon and during the Skylab Program began with a layer of neoprene-coated nylon ripstop. This was the innermost layer of protection from micrometeoroids. Next, thermal radiation protection was provided by five layers of aluminized PET film (Mylar), alternating with four layers of nonwoven Dacron, which provided thermal spacing, followed by two layers of aluminized polyimide Kapton film and Beta cloth marquisette laminate. The outermost layer of PTFE (Teflon)-coated filament Beta cloth was non-flammable and provided abrasion protection from the notoriously abrasive lunar dust. This layer was supplemented with Teflon abrasion patches at the knees and other areas.[1]

Space Shuttle/EMU suit

The construction of the TMG on the EMU suits in use on the Space Shuttle and International Space Station differs somewhat from the construction of the Apollo/Skylab TMG.

The EMU TMG includes seven layers of aluminized Mylar laminated with Dacron, rather than five, and eliminates the use of Kapton. The outermost layer is white Ortho-Fabric, made with a blend of Gore-Tex, Kevlar, and Nomex. This layer can withstand temperatures from −300° to +300° Fahrenheit (-184.4 to 149 Celsius). The outer layer provides both micrometeoroid and thermal protection, by reflecting most of the sun's thermal radiation.[2]