Lightweight garage #29 James Webb Telescope @ NASA, ESA, CSA

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Lightweight garage, News

27.10.2022 Luca Wilhelmy

The vehicle

Behind this gate is the latest scientific device for observing space. The James Webb Telescope was sent on its journey from the Guiana Space Center on 25.12.2021 with a launch weight of 6.2 tons. After several days and at a maximum speed of 9.90 km/s (35640 km/h), the James Webb Telescope reached its destination. At the Lagrange point L2, approximately 1.5 million km from the earth, the telescope is now moving in line with the earth and the sun. After calibration, the James Webb Telescope is now able to observe a ring-shaped section of about 39% of the sky.

©NASA, Model of the unfolded James Webb Telescope

The technology

The telescope consists of various assemblies. The first assembly relevant to lightweight construction is the 21.2 m x 14.2 m sunshield. The shield consists of 5 layers of Kapton, a polyamide film with a 100 nm thin aluminum layer. Apart from the first foil facing the sun, these are just 25 μm thick. The first film is also covered with a 50 nm thick silicon layer. The energy required for observation is supplied by a 2000 W solar module, which is located in front of the solar shield. The telescope's optics are located on the side facing away from the sun in order to reduce infrared radiation from the sun and the moon. The primary mirror has a diameter of 6.5 m, with the 18 hexagonal segments forming the mirror surface. Due to its low density, high strength and low coefficient of thermal expansion at temperatures below 100 K, beryllium was chosen as the material for the segments. The segment plates were designed in such a way that they can be aligned and at the same time withstand micrometeorites. The segments are additionally coated with a layer of gold and a layer of silicon dioxide.

©NASA, Illustration of the folding mechanism

The lightweight aspect

The entire telescope offers an impressive impression of lightweight construction. By combining different materials, the different properties of each material are utilized. The material properties can be optimally utilized through the arrangement of the components. Everything is connected by complex mechanics and sensors for calibration, position determination and heat regulation. Due to transportation and the limited packing size in the rocket, the components must also be deployable, which represents a considerable risk. 

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