View source for Astronomy:Thermal Micrometeoroid Garment

{{Short description|Outer, protective layer of a spacesuit}}
[[File:Thermal Micrometeoroid Garment.gif|frame|Cross-section of layers in space suit construction]]

An ('''Integrated''') '''Thermal Micrometeoroid Garment''' ('''TMG''' or '''ITMG''') is the outer layer of a [[Astronomy:Space suit|space suit]].  The TMG has three functions: to insulate the suit occupant and prevent heat loss, to shield the occupant from harmful [[Physics:Solar radiation|solar radiation]], and to protect the astronaut from [[Astronomy:Micrometeoroid|micrometeoroid]]s and other orbital debris, which could puncture the suit and depressurize it. (This latter function is provided for spacecraft by Micrometeoroid and Orbital Debris (MMOD) Protection systems.<ref>{{cite web
 | url                 = http://www.nasa.gov/externalflash/ISSRG/pdfs/mmod.pdf
 | archive-url          = https://web.archive.org/web/20101226102151/http://www.nasa.gov/externalflash/ISSRG/pdfs/mmod.pdf
 | archive-date         = December 26, 2010
 | title               = Micrometeoroid and Orbital Debris (MMOD) Protection
 | publisher           = NASA
 | url-status          = dead
 | access-date          = 2013-05-10
}}</ref>)

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

==A7L suit (Apollo/Skylab)==
[[Image:Beta cloth penetration.jpg|thumbnail|Micrometeoroid impacts in Beta cloth]]
Outside a [[Astronomy:Liquid Cooling and Ventilation Garment|Liquid Cooling and Ventilation Garment]], pressure bladder, and restraint layer, the TMG for the A7L suit worn on the Moon and during the [[Engineering:Skylab|Skylab]] Program began with a layer of [[Chemistry:Neoprene|neoprene]]-coated [[Chemistry:Nylon|nylon]] ripstop.  This was the innermost layer of protection from micrometeoroids.  Next, [[Physics:Thermal radiation|thermal radiation]] protection was provided by five layers of [[Chemistry:Aluminum|aluminized]] PET film (Mylar), alternating with four layers of nonwoven Dacron, which provided thermal spacing, followed by two layers of aluminized [[Chemistry:Polyimide|polyimide]] [[Chemistry:Kapton|Kapton]] film and [[Engineering:Beta cloth|Beta cloth]] marquisette laminate. The outermost layer of [[Chemistry:Polytetrafluoroethylene|PTFE]] ([[Engineering:Teflon|Teflon]])-coated filament Beta cloth was non-flammable and provided [[Physics:Abrasion (mechanical)|abrasion]] protection from the notoriously abrasive lunar dust. This layer was supplemented with Teflon abrasion patches at the knees and other areas.<ref>{{cite book
  | last = Carson
  | first = Maurice A.
  |author2=Rouen, Michael N. |author3=Lutz, Charles C. |author4=McBarron, James W. II 
  | title = Biomedical Results of Apollo - Section VI - Chapter 6 - Extravehicular Mobility Unit
  | publisher = Lyndon B. Johnson Space Center
  | url = https://history.nasa.gov/SP-368/s6ch6.htm
  }}
</ref>

==EMU suit (Space Shuttle/ISS)==
The construction of the TMG on the EMU suits in use on the [[Engineering:Space Shuttle|Space Shuttle]] and [[Astronomy:International Space Station|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 [[Chemistry:Gore-Tex|Gore-Tex]], [[Chemistry:Kevlar|Kevlar]], and [[Engineering:Nomex|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.

==References==
{{reflist}}

{{space suit}}
{{Apollo program hardware}}

[[Category:Human spaceflight]]
[[Category:Space suit components]]

{{Sourceattribution|Thermal Micrometeoroid Garment}}