![]() ![]() Layer 1, which will face the sun, is only 0.05mm thick, while the other four layers are just 0.025 mm thick. "The fifth layer is mostly for margin against imperfections, micro-meteoroids holes, etc." The gap between the layers provides an additional insulating effect.Įach layer of the sunshield is incredibly thin. "The five layers are needed to block and re-direct enough heat to get the telescope down to required temperatures, with margin," Cooper added. "Heat generated by the spacecraft bus at the ‘core’, or center, is forced out between the membrane layers so that it cannot heat up the optics." ![]() "The shape and design also direct heat out the sides, around the perimeter, between the layers," explained James Cooper, Webb telescope sunshield manager at NASA's Goddard Space Flight Center in Greenbelt, Maryland. Each of the different layers are positioned and separated with precision to accomplish their function. The kite-like shape of the sunshield and the number of layers both play an important role. The highly-reflective aluminum surfaces also bounce the remaining energy out of the gaps at the edges of the sunshield’s layers. Silicon has a high emissivity, which means it efficiently emits heat and light, and so acts to block the sun's heat from reaching the infrared instruments that will be located underneath it. This is done so that the layers can be electrically grounded to the rest of the JWST and to ensure they will not build up a static electric charge across their surface. The doping process involves mixing in a small amount of another material during the silicon coating process to make the coating electrically conductive. The sunshield layers are coated with aluminum and doped-silicon to take advantage of their optical properties and longevity in the space environment. On Earth, Kapton polyimide film is used in a variety of electrical and electronic insulation applications. It has high heat-resistance and remains stable across a wide range of temperatures from -269☌ to 400☌, and does not melt or burn at the highest of these temperatures. Kapton is a polyimide film that was developed by DuPont in the late 1960s. The sunshield is a critical part of the JWST, which is due to be launched in October 2018, because the infrared cameras and instruments aboard must be kept very cold and out of the sun's heat and light if they are to function properly. Each layer is coated with aluminum, while the sun-facing side of the two hottest layers (designated layer 1 and layer 2) are also coated with doped-silicon (or treated silicon) to reflect the sun's heat back into space. The sunshield consists of five layers of a material called Kapton. ![]() There are even special seams and reinforcements to limit meteorite damage. Each layer is made from a unique composite material, each has a specific thickness and size, and all the layers must be precisely separated in space. ![]() In order to protect the mirrors and instruments aboard the James Webb Space Telescope (JWST) from solar radiation, NASA and its industry partners have come up with a lightweight, five-layer sunshield that is a complex and innovative feat of material science and engineering. A NASA engineer in a cleanroom looks at one of the sunshield layers with a grid pattern of ‘rip-stops’. ![]()
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