How can something so thin keep you warm? Even though it sounds cliché, it's space age technology.
Manufacturers created the material by depositing vaporized aluminum onto a very thin plastic film. The resulting material is thin, flexible and thermal-reflective -- meaning it reflects heat. The aluminum helps redirect infrared energy, which is just a fancy word for heat. Depending on how the blanket is made, it can reflect heat away (that's how NASA used it to cool down Skylab), or it can reflect heat in (that's how it regulates body temperature). Sometimes called a passive warming system, space blankets assist the body in conserving that infrared energy.
Let's focus on how space blankets work to keep a person warm. First, we need to understand how a body loses heat in the first place. Excessive heat loss leads to hypothermia, an extremely dangerous condition. Space blankets stop both evaporative and convective heat loss.
Evaporation is the process of water changing from a liquid to a gas. In the case of a person, the liquid can be sweat or wet clothing. Evaporation uses a lot of energy and lowers the body temperature. This is why you need to be careful not to get too sweaty in cold weather. Your body temperature will drop quickly once you stop exerting yourself -- and the evaporation of sweat will make you even colder. To prevent evaporative heat loss, you should try to stay as dry as possible. A space blanket helps slow down the process of evaporative heat loss by increasing the humidity of the air next to the skin.
Convection is a lot like conduction. Conduction is the transfer of heat or cold between two objects. For example, if you sit down on a pile of snow, your backside will get colder, and the snow will get warmer. With convective heat loss, however, the cold object is moving -- like a cold wind. The wind takes the warmth away from whatever it touches. The faster the object is traveling, the colder you'll get. You can help reduce convective heat loss by wearing layers of clothing as insulation. A space blanket forms a barrier between the wearer and the wind, providing insulation.
Lastly, we also lose body heat through radiation -- it simply radiates off our body. The reflective agent on space blankets -- usually silver or gold -- reflects about 80 percent of our body heat back to us.
Next up, we'll talk about the many ways you can use a space blanket for survival.