|Multi-layer insulation blankets consist of multiple layers of thin plastic film, coated on one or both sides with an aluminized reflective material. (Image source: Web Industries)|
With increasing numbers of exploratory spacecraft and constellations of small satellites proliferating in the distant skies, demand is rising for multi-layer insulation (MLI) materials. The materials, which play a critical thermal management function, are visible as the shiny, reflective areas on the outside of satellites and other space-traveling vehicles.
Often called blankets, MLI components are a type of lightweight insulation that protects a vehicle’s occupants, electronics, and equipment from the damaging effects of radiated heat. While in orbit, space vehicles face an extremely challenging temperature environment. They can be exposed to direct or indirect sunlight at one moment and then plunged into total darkness the next. Temperature variations during a single orbit can range from lows of -450ºF to highs of 250ºF. In addition, a vehicle’s instrumentation and equipment can generate a considerable amount of heat that must be controlled.
In the vacuum of space, where there is significant exposure to thermal radiation but minimal conduction or convection, MLI blankets provide exceptional insulating properties. For example, a foot of standard insulating material on Earth might have an R value of 24 to 30. In comparison, MLI blankets in space have an insulating effectiveness equivalent to about R=10,000. They help manage a spacecraft’s thermal profile by protecting against extremes of heat and cold.
The Form and Function of MLI
MLI blankets consist of multiple layers of thin plastic film, coated on one or both sides with an aluminized reflective material. A typical blanket for space applications can have 10, 20, or more layers, with about ½-inch thickness overall. Between the layers is a nonwoven mesh