CM – NASA’s Webb telescope stays cool with ultra-thin Kapton polyimide films from DuPont

After 30 years of development, the James Webb Space Telescope (JWST) of the National Aeronautics Space Administration (NASA) took off on December 25, 2021 from the launch site of the European Space Agency in Kourou, French Guiana. DuPont technology in the form of ultra-thin Kapton polyimide films is the key material that protects the JWST from light and solar heat so that it functions properly in space.

Space is one of the most hostile and extreme environments imaginable. Above Earth’s insulating atmosphere, spacecraft are exposed to extreme temperatures, both hot and cold, and there is a significantly increased risk of radiation damage.

« The excellent thermal and mechanical properties of Kapton polyimide film make it an ideal material for aerospace applications, » said Tim Scott, director of business development, aerospace and defense, DuPont Electronics and Industrial. « For more than 50 years, Kapton polyimide film has been an integral technological material in support of spacecraft missions starting with the Apollo 11 mission in July 1969. »

The $ 10 billion JWST is the largest space telescope ever built and features an extendable mirror more than 21 feet in diameter made up of 18 hexagonal mirror segments. The gold-plated beryllium mirror segments are more than eight feet in diameter and focus on four main areas: first light in the universe, formation of galaxies in the early universe, birth of stars and protoplanetary systems, and planets (including the origins of life.)

At the heart of the JWST is the Integrated Science Instrument Module (ISIM), a suite of four instruments including a near-infrared camera, a mid-infrared instrument, a fine control sensor, and two different near-infrared spectrographs.

The JWST is the successor to the 30-year-old Hubble Space Telescope and improves Hubble in two ways. The first is its size: Hubble is about the size of a school bus, while Webb is about half the size of a 737 airplane. The Hubble mirror is approximately eight feet in diameter, while the JWST retractable mirror is over 21 feet in diameter, 100 times stronger than the Hubble.

The JWST operates near Earth-Sun L2 (Lagrange point), approximately 1,500,000 km (930,000 miles) out of orbit. For comparison, Hubble orbits 550 km (340 miles) above the Earth’s surface, and the moon is approximately 400,000 km (250,000 miles) from Earth.

The key to the performance of the JWST is a five-layer sun protection that prevents sunlight and background heat from interfering with the ISIM instruments. The sun visor is a diamond-shaped system made of five layers of Kapton polyimide film with a length of about 21 meters and a width of 47 meters. Each layer of the Kapton polyimide film is coated with aluminum, and the sun-facing side of the two hottest layers (layer 1 and layer 2) is also provided with a treated silicone coating to reflect the heat of the sun back into space.

Each layer of Kapton polyimide film sun protection is incredibly thin. Layer 1 faces the sun and is only 50 micrometers (0.002 inches) thick, while the other four layers of Kapton polyimide film are 25 micrometers (0.001 inches). The thickness of the aluminum and silicone coatings are even less.

The silicon coating is approximately 0.05 micrometers (50 nanometers) thick while the aluminum coating is approximately 0.1 micrometers (100 nanometers) thick. JWST’s sun visor was origami-style folded twelve times to fit inside the Ariane 5 rocket, so the Kapton polyimide film layers had to be ultra-thin.

The Kapton enabled sunshade is a critical part of the Webb telescope design as the infrared cameras and instruments on board must be kept very cold, below -370 F, and out of the heat and light of the sun to function properly.

Each subsequent layer of sun protection is cooler than the one below. The sun protection divides the observatory into a warm side facing the sun with a maximum temperature of the outermost layer of 110 ° C and a cold side with a minimum temperature of around -236 ° C.

This is not the first time NASA has selected DuPont technology to protect spacecraft designed for reconnaissance missions. For more than 50 years, DuPont has proven that its technology works reliably in the face of extreme temperature fluctuations, atomic oxygen, particle and electromagnetic radiation, space debris and other space weather conditions to which satellites are exposed. As space missions become more complex, DuPont continues to research and develop new robust variations of Kapton to better withstand the unique conditions in space.