Spikes for silence

ESA Space in Images These spiky carbon-impregnated foam pyramids, seen here in ESA's Hertz test chamber, cover the walls of facilities that simulate the endless void of space. This 'anechoic' foam absorbs radio signals, enabling radio-frequency testing without any distorting reflections from the chamber walls. In addition, it also absorbs sound - making these chambers eerily quiet places to work. ESA's Hertz chamber , in its technical centre in the Netherlands, is an isolated metal-walled chamber offering versatile ways of measuring a subject's radio-frequency performance. Its walls block all external electromagnetic energy such as TV broadcasts and mobile phone signals for uninterrupted testing. Other ESA radio-frequency testing facilities - including the smaller Compact Antenna Test Range and the Maxwell chamber for assessing the electromagnetic compatibility of satellite systems - are similarly clad with foam.