History
The earliest forms of RAM were the materials called Sumpf and Schornsteinfeger, a coating used in Germany during the World War II for the snorkels (or periscopes) of submarines, to lower their reflectivity in the 20-centimeter radar band the Allies used. The material had a layered structure and was based on graphite particles and other semiconductive materials embedded in a rubber matrix. The material's efficiency was partially reduced by the action of sea water.
Germany also pioneered the first aircraft to use RAM during World War II, in the form of the Horten Ho 229. It used a carbon-impregnated plywood that would have made it very stealthy to Britain's primitive radar of the time. It is unknown if the carbon was incorporated for stealth reasons or because of Germany's metal shortage.
Read more about this topic: Radar-absorbent Material
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