A heat shield is designed to shield a substance from absorbing excessive heat from an outside source by either dissipating, reflecting or simply absorbing the heat. It is often used as a form of Exhaust Heat Management

Exhaust heat management

Exhaust Heat Management is the means of lessening the negative effects of internal combustion engine exhausts by preventing heat from escaping the exhaust system on automobiles.-Overview:...

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Uses

Automotive

Due to the large amounts of heat given off by internal combustion engines, heat shields are used on most engines to protect components and bodywork from heat damage. As well as protection, effective heat shields can give a performance benefit by reducing the underbonnet temperatures, therefore reducing the intake temperature. Heat shields vary widely in price, but most are easy to fit, usually by stainless steel clips or high temperature tape. There are two main types of automotive heat shield:

• The Rigid heat shield has, until recently, been made from solid steel, but is now often made from aluminium. Some high-end rigid heat shields are made out of aluminium sheet or other composites, with a ceramic thermal barrier coating to improve the heat insulation.
• The Flexible heat shield is normally made from thin aluminium sheeting, sold either flat or in a roll, and is bent by hand, by the fitter. High performance flexible heat shields sometimes include extras, such as ceramic insulation applied via plasma spraying. These latest products are commonplace in top-end motorsports such as Formula 1.

As a result, a heat shield is often fitted by both amateur and professional personnel during a phase of engine tuning

Engine tuning

Engine tuning is the adjustment, modification or design of internal combustion engines to yield optimal performance, to increase an engine's power output, economy, or durability....

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Space

Spacecraft which land on a body

Astronomical object

Astronomical objects or celestial objects are naturally occurring physical entities, associations or structures that current science has demonstrated to exist in the observable universe. The term astronomical object is sometimes used interchangeably with astronomical body...

 with an atmosphere

Atmosphere

An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...

, such as Earth

Earth

Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

, Mars

Mars

Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...

 and Venus

Venus

Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...

, currently do so by entering at high speeds, depending on friction rather than rocket power to slow the craft. A side effect of this is aerodynamic heating

Aerodynamic heating

Aerodynamic heating is the heating of a solid body produced by the passage of fluid over a body such as a meteor, missile, or airplane. It is a form of forced convection in that the flow field is created by forces beyond those associated with the thermal processes...

, which in the case of an Earth reentry can be destructive. An aerodynamic heat shield consists of a protective layer of special materials to dissipate the heat. Two basic types of aerodynamic heat shield have been used:

• An ablative heat shield consists of a layer of plastic resin, the outer surface of which is heated to a gas which carries the heat away by convection
  Convection
  Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....
  
  . Such shields were used on the Mercury, Gemini and Apollo
  Apollo spacecraft
  The Apollo spacecraft was composed of five combined parts designed to accomplish the American Apollo program's goal of landing astronauts on the Moon by the end of the 1960s and returning them safely to Earth...
  
   spacecraft.
• A thermal soak heat shield uses an insulating material to absorb and radiate the heat away from the spacecraft structure. This type was used on the Space Shuttle
  Space Shuttle
  The Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...
  
  , consisting of fiberglass tiles over most of the vehicle surface, with reinforced carbon-carbon
  Reinforced carbon-carbon
  Carbon fibre-reinforced carbon is a composite material consisting of carbon fibre reinforcement in a matrix of graphite. It was developed for the nose cones of intercontinental ballistic missiles, and is most widely known as the material for the nose cone and wing leading edges of the Space Shuttle...
  
   material on the highest heat load points, the nose and wing leading edges. Damage to this material on a wing caused the 2003 Space Shuttle Columbia disaster
  Space Shuttle Columbia disaster
  The Space Shuttle Columbia disaster occurred on February 1, 2003, when shortly before it was scheduled to conclude its 28th mission, STS-107, the Space Shuttle Columbia disintegrated over Texas and Louisiana during re-entry into the Earth's atmosphere, resulting in the death of all seven crew members...
  
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Some spacecraft also use a heat shield (in the conventional automotive sense) to protect fuel tanks and equipment from heat produced by a large rocket engine

Rocket engine

A rocket engine, or simply "rocket", is a jet engineRocket Propulsion Elements; 7th edition- chapter 1 that uses only propellant mass for forming its high speed propulsive jet. Rocket engines are reaction engines and obtain thrust in accordance with Newton's third law...

. Such shields were used on the Apollo Service Module and Lunar Module

Apollo Lunar Module

The Apollo Lunar Module was the lander portion of the Apollo spacecraft built for the US Apollo program by Grumman to carry a crew of two from lunar orbit to the surface and back...

 descent stage.

Industry

Heat shields are often used to protect heat-sensitive components used in various industrial processes.

Firearms

Heat shields are often affixed to semi-automatic

Semi-automatic firearm

A semi-automatic, or self-loading firearm is a weapon which performs all steps necessary to prepare the weapon to fire again after firing—assuming cartridges remain in the weapon's feed device or magazine...

 or automatic

Automatic firearm

An automatic firearm is a firearm that loads another round mechanically after the first round has been fired.The term can be used to refer to semi-automatic firearms, which fire one shot per single pull of the trigger , or fully automatic firearms, which will continue to load and fire ammunition...

rifles and shotguns in order to protect the user's hands from the heat caused by firing shots in rapid succession.