What Is a Heat Shield?

M. McGee

A heat shield is a substance that protects something from excess heat. There are three basic forms of heat shield, and each protects in a different way. A dissipating shield takes in heat and spreads it out over a large surface area in order to pull it away from the heat source. An absorbing shield takes in the heat and holds on to it; the shields typically have a large layer of insulation underneath them that protects the lower components. Lastly, a reflecting shield will redirect the heat away from the shielded object without absorbing any of the warmth. These shields are found in a wide range of products, from firearms to airplanes.

Heat-resistant ceramic tiles were used to protect the Space Shuttle's exterior during re-entry.
Heat-resistant ceramic tiles were used to protect the Space Shuttle's exterior during re-entry.

Generally, a heat shield is a layer of material that is specially designed to interact with heat in a specific way. This layer will wrap around the protected item, forming an outer shell. The design of this shell varies based on the type of shield and material used to build it. In some cases, rather than a single layer, a heat shield will be an entire system that funnels and channels heat out of a device.

The most common heat shields are made of aluminum, steel and ceramic. Steel is the least efficient of the three materials, but is common in places where cost is important and weight is not. A steel shield is typically a pre-formed rigid plate that fits over a specific component. These plates are inexpensive but are cumbersome and heavy. Aluminum is a common alternative to steel; it is lighter, absorbs more heat and it is possible to make aluminum flexible so prefabrication isn’t necessary.

Ceramic is widely considered the best material for common heat shielding. These shields are light, durable and conduct heat very well. For a long time, the only drawback was their rigidity; much like steel, they needed to be prefabricated. This drawback was removed in the early part of the 21st century when a flexible aluminum-backed ceramic system was introduced to the market.

Many products contain a heat shield. The two most common places for normal consumers to encounter one of these shields is within guns with high rates of fire and performance automobile engines. In both cases, the shield protects the surrounding material from the heat created from explosive combustion. These shields are also common in certain manufacturing machines such as grinders and lathes. Even still, the most famous heat shields are likely found on high-speed aircraft like jets and space shuttles where they protect the devices from the air friction generated by high-speed flight.

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