Multi-layer insulation
Multi-layer insulation, or MLI, is thermal insulation composed of multiple layers of thin sheets and is often used on spacecraft. It is one of the main items of the spacecraft thermal design, primarily intended to reduce heat loss by thermal radiation. In its basic form, it does not appreciably insulate against other thermal losses such as heat conduction or convection. It is therefore commonly used on satellites and other applications in vacuum where conduction and convection are much less significant and radiation dominates. MLI gives many satellites and other space probes the appearance of being covered with gold foil.
Additional properties
Spacecraft also may use MLI as a first line of defense against dust impacts. This normally means spacing it a cm or so away from the surface it is insulating. Also, one or more of the layers may be replaced by a mechanically strong material, such as beta cloth.
In some applications the insulating layers must be grounded, so they cannot build up a charge and arc, causing radio interference. Since the normal construction results in electrical as well as thermal insulation, these applications may include aluminum spacers as opposed to cloth scrim at the points where the blankets are sewn together.
See also
- Liquid hydrogen tank car, on which a form of multi-layer insulation is applied
- Thermal Control Subsystem
References
External links
- "As Good as Gold: Are satellites covered in gold foil?". National Environmental Satellite, Data, and Information Service. January 8, 2016.
- Satellite Thermal Control Handbook, ed. David Gilmore. ISBN 1-884989-00-4. In particular, Chapter 5, Insulation, by Martin Donabedian and David Gilmore.
- Tutorial on temperature control of spacecraft by JPL
- "Cassini dons its thermal cloak" (Press release). NASA JPL. 1997-01-03. Archived from the original on 2007-09-04. Retrieved 2009-01-08.
- Typical specialist article on tests of Cassini's MLI