​​What is Space Blanket?

But sometimes the most effective way to protect persons or devices from leakage or gain of heat is to use a thermal radiation insulator. 

Thermal radiation does not require any medium for energy transfer.

Moreover, energy transfer by radiation is fastest (at the speed of light) and it suffers no attenuation in a vacuum.

The highly reflective insulators are often included in emergency kits (therefore emergency thermal blankets) and are also used by long-distance runners after finishing a race to avoid a large swing in body temperature. Space blankets are designed to reflect heat back to body or deflect heat when used as a shelter from the sun, they can be used to insulate everything from the Mars rovers to marathon runners, from satellites to sun shields, and from rockets to residences.

It is one of the simplest, yet most versatile spinoffs to come out of the Agency. Highly reflective foils in radiant barriers and reflective insulation systems reflect radiant heat away from persons and living spaces, making them particularly useful in very cold climates.