"Multi-layer insulation" (MLI) is a type of thermal insulation that is used to protect spacecraft and other aerospace vehicles from extreme temperatures. It consists of multiple layers of thin, reflective material, such as aluminum or other reflective materials, separated by thin layers of insulating material. The multiple layers of MLI are designed to reflect and absorb radiant heat, helping to keep the temperature inside the spacecraft or vehicle within a comfortable range for the occupants and equipment.
MLI is often used on spacecraft and other aerospace vehicles to protect them from the extreme temperatures encountered in space, where temperatures can vary significantly depending on the vehicle's location and orientation relative to the Sun. It is also used on Earth-based aerospace vehicles, such as missiles and high-altitude aircraft, to protect them from extreme temperatures encountered during flight.
MLI is typically lightweight and flexible, making it well-suited for use in the aerospace industry. It is also durable and resistant to damage, which is important for the harsh environments encountered in space and in high-altitude flight.