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Using multi-layer insulation materials for space vehicle design

Posted: 18 Jul 2012     Print Version  Bookmark and Share

Keywords:Multi-Layer Insulation  Other Services 

A more common and more effective method is to separate and support layers of two-side-aluminized film using a thin layer of a poor thermal conductor. Fibreglass material, paper, cloth, and various polymer non-woven or meshes can be used. An additional benefit of this method is that the non-conductive layer provides added puncture resistance and overall creates a more robust construction.

Additionally, the two-side-aluminized films offer lower absorptance because they reflect radiation on both the first and second surface.

Most MLI blankets are based on three foundations, polyester, polyimide or fluorocarbon films. These base materials are metalized, coated, laminated, perforated, crinkled or embossed or some combination to meet different product specifications. For perspective, an MLI film manufacturer could have a product portfolio of over 400 products based on the three aforementioned film types.

The films are the base layer for TPS and are selected for a few key properties including physical, thermal, electrical and chemical (table).

Some MLI blankets use coated films in addition to metalisation. Various coatings are used for corrosion resistance, controlling emittance and bonding dissimilar substrates together.

New technologies
External insulation materials are sensitive to electromagnetic interference (EMI), particularly in LEO and medium earth orbit (MEO) due to EMI from the Van Allen radiation belt. Existing metallic coatings that are clear and electrically conductive (Less than 1000 ohms per square), and used to dissipate the charge build-up, have been used but are subject to cracking and handling damage. Next generation polymer based coatings can be incorporated into MLI blankets to improve the flexibility of the insulation allowing for more robust construction.

Other new technologies are constantly being tested for use in space vehicles, for example:

 • Integration of new film barrier technologies in combination with advanced composites, including nano-fibres and 3-D woven materials, are applied for their ability to produce very strong, thick materials.
 • Combination of solar energy modules as an active insulation component with the passive MLI that insulates without using electrical or other forms of power.
 • Use of advanced barrier coatings to further prevent electrical interference and oxidation of components in LEO.

Steady growth in satellite applications and work on the ISS over the coming years will serve as a proving ground for optimisation of current MLI materials as well as this new generation of specialised materials. The intent of these materials is to provide more reliable, long term service, while at the same time enhancing the performance of the space vehicle and its instruments throughout its life. The challenge will be to provide coated films and fabrics with improved thermal resistance, optical and physical protection properties at the same or less weight as current materials used, and thereby enabling engineers to apply them to areas where only heavier materials have worked in the past.

About the author
As business development manager for the Global Aerospace Products Group at Dunmore Corporation, Art Mallett, Jr. leads the team that develops innovative materials for the aerospace industry, including DunShield ESD and aircraft Thermal Acoustic Insulation. He holds a bachelor of science in aerospace engineering from the Florida Institute of Technology (FIT) and is a member of the American Institute of Aeronautics and Astronautics (AIAA). Art regularly participates and speaks at AIAA events, most recently speaking about "Advances In Materials for Multi-Layer Insulation" at the AIAA Space 2011 Conference in September 2011.

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