Space blanket
Aspace blanket(also known as aMylarblanket,emergency blanket,first aid blanket,safety blanket,thermal blanket,weather blanket,heat sheet,foil blanket,orshock blanket) is an especially low-weight, low-bulkblanketmade ofheat-reflectivethin plastic sheeting. They are used on the exterior surfaces of spacecraft for thermal control, as well as by people. Their design reduces the heat loss in a person's body, which would otherwise occur quickly due to thermal radiation, water evaporation, or convection. Their low weight and compact size before unfurling make them ideal when space or weight are at a premium. They may be included infirst aid kitsand with camping equipment. Lost campers and hikers have an additional possible benefit: the shiny surface flashes in the sun, allowing its use as an improviseddistress beaconforsearchersand as a method of signalling over long distances to other people.[1]
Manufacturing
[edit]
First developed byNASA'sMarshall Space Flight Centerin 1964 for the US space program,[2][3][4] the material comprises a thin sheet ofplastic(oftenPET film) that is coated with ametallic,reflectingagent, making itmetallized polyethylene terephthalate(MPET) that is usually gold or silver in color, which reflects up to 97% ofradiatedheat.[5][6]
For use in space,polyimide(e.g.Kapton,UPILEX) substrate is usually chosen due to its resistance to the hostilespace environment,large temperature range (cryogenic to −260 °C and for short excursions over 480 °C), lowoutgassing(making it suitable forvacuum use), and resistance toultravioletradiation. AluminizedKapton,with foil thickness of 50 and 125 μm, was used on theApollo Lunar Module.[7]The polyimide gives the foils their distinctive amber-gold color.
Space blankets are made byvacuum-depositinga very precise amount of purealuminumvapor onto a very thin, durable film substrate.[8]
Usage
[edit]In their principal usage, space blankets are included in many emergency,first aid,and survival kits because they are usually waterproof and windproof. That, along with their low weight and ability to pack into a small space, has made them popular among outdoor enthusiasts and emergency workers. Space blankets are often given tomarathonersand other endurance athletes at the end of races, or while waiting before races if the weather is chilly.[9]The material may be used in conjunction with conductive insulation material and may be formed into a bag for use as abivouac sack(survival bag).[10][11]
Infirst aid,[12]the blankets are used to prevent or counterhypothermia.A threefold action facilitates this:
- The airtight foil reducesconvection
- Heat loss caused byevaporationofperspirationis reduced[13]
- Thereflectivesurface inhibits losses caused bythermal radiation
In a hot environment, they can be used to provide shade or protection against radiated heat, but using them to wrap a person would be counterproductive, becausebody heatwould get trapped by the airtight foil. This effect would exceed any benefit gained from heat reflection to the outside. Wearing a space blanket produces an insignificantly slower cooling rate after running in hot, humid conditions.[14]
Space blankets are used to reduce heat loss from a person's body, but as they are constructed ofPET film,they can be used for other applications for which this material is useful, such as insulating containers (e.g. DIY solar concentrators) and other applications.
In addition to the space blanket, theUnited States militaryalso uses a similar blanket called the "casualty blanket". It uses a thermal reflective layer similar to the space blanket, backed by anolive drab-colored, reinforcing, outer layer. It provides greater durability and warmth than a basic space blanket at the cost of greater bulk and weight. It is also used as a partial liner inside the layers of bivouac sacks in very cold weather climates.[15]Space blankets were also used by theTalibanto hide their heat signature from NATO forces.[16][17]
See also
[edit]- Emergency shelter
- Emissivity
- R-value (insulation)
- Radiant barrier
- Reflectivity
- Thermal insulation
- Thermoregulation
- Thin-film deposition
References
[edit]- ^"How Space Blankets Work".howstuffworks.com.24 November 2009.Retrieved14 September2018.
- ^Hall, Loura (15 September 2016)."Reflecting on Space Benefits: A Shining Example".NASA Center for AeroSpace Information.Archived fromthe originalon 2 February 2007.Retrieved14 September2018.
- ^Huntington, Tom."Bringing NASA Down to Earth."AmericanHeritage.com. 2008.
- ^ Bryan, Will (May 11, 2016)."The Space Blanket: Your Adventure Companion".The Marshall Star.NASA.RetrievedMay 11,2016.
- ^Reflective Insulation Test data.
- ^Speik, Robert."Emergency space blankets provide a false sense of security".traditionalmountaineering.org.Retrieved14 September2018.
- ^Paul Fjeld."Lunar Module Coatings".home.earthlink.net.Retrieved14 September2018.
- ^"Space Blankets".Retrieved12 March2016.
- ^"General Guidelines for Recycling at Mass Participant Sporting Events."AFMInc. 2008.
- ^"Emergency Shelter"REI.
- ^"Full Wrap on Space Blankets."Runner's World. 2005.
- ^Buggy, D.; Hughes, N. (1 April 1994)."Pre-emptive use of the space blanket reduces shivering after general anaesthesia".British Journal of Anaesthesia.72(4): 393–396.doi:10.1093/bja/72.4.393.PMID8155437.
- ^"How Body Heat is Lost."Survival Topics.
- ^REYNOLDS, KORY; EVANICH, JOHN (2015)."Reflective Blankets Do Not Effect Cooling Rates after Running in Hot, Humid Conditions".Int J Exerc Sci.72(4): 393–6.doi:10.1093/bja/72.4.393.PMC4831857.PMID8155437.
- ^"How to Choose Bivy Sacks".REI.Retrieved14 September2018.
- ^"Afghanistan: Patrolling the most attacked base".BBC.5 December 2011.Retrieved5 December2011.
- ^Smucker, Philip."U.S. soldiers' options limited to protect Afghans from Taliban."The State. Jun. 2, 2009.
External links
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Media related toSpace blanketsat Wikimedia Commons
