An image of the Fluid Telescope Experiment (FLUTE), which uses a material that flows like water to create a super-large lens in space. The fluid telescope has been proposed as a way to build a giant lens that has never been attempted before. Courtesy of Elamaru Studio
The James Webb Space Telescope, which left Earth last year, went into commissioning. Scientists plan to unravel the mysteries of the universe by making state-of-the-art space telescopes such as the Lubua Space Telescope and the Nancy Grace Roman Space Telescope. Meanwhile, research is underway to make a super-large lens in space with a material that flows like water. The Fluid Telescope Experiment (FLUTE). Why did they set out to develop new space telescope materials?
The James Webb Space Telescope, launched in December of last year, boasts a gigantic size of 6.5 meters in diameter. That’s 2.7 times that of the Hubble Space Telescope. The massive James Webb Space Telescope weighs only 6.2 tons. That’s half the weight of the Hubble Space Telescope, which weighs 12.2 tons.
The Ariane 5 rocket used to launch the James Webb Space Telescope can carry a payload of up to 20 tons to low Earth orbit and 10 tons to geostationary orbit. The success of the James Webb Space Telescope’s awakening in space is thanks to advances in materials. The main mirror of the James Webb Space Telescope was made of beryllium, the fourth lightest element.
Space telescope diet to go to space
The construction process of the James Webb Space Telescope, which went into space last year. Despite its gigantic size, it is light compared to its gigantic size as the main mirror is made of beryllium, which is the fourth lightest among elements. Provided by the National Aeronautics and Space Administration (NASA)
The biggest obstacles to sending a space telescope into space are its size and weight. Typically, the performance of a telescope depends on the size of the lenses and reflectors. The larger the size of the telescope, the greater the light-collecting power, which is the ability to receive light, and the better the resolution that distinguishes two objects at a short distance. This means that it can accurately capture darker light from farther away. However, it takes a long time and a lot of money to build a giant space telescope and launch it into space. The James Webb Space Telescope cost 10 billion dollars (regarding 12.78 trillion won).
For this reason, research on materials for space telescope lenses and reflectors has been developed in the direction of developing lighter materials as well as those that can withstand extreme environments. In the past, tempered glass or ceramic materials were mainly used. In recent reflectors, silicon carbide (SiC) is mainly used. When it is the same size as the glass used for lenses, it weighs regarding one-third, and the structure hardly changes even at cryogenic temperatures. A reflector made of silicon carbide was also used in the cameras mounted on the comet probe Rosetta and the Pluto spacecraft New Horizons. There are also materials that are lighter and stronger than this. “Recently, we are testing the suitability of carbon fiber reinforced plastic (CFRP),” said Kim Young-soo, senior researcher at the Astronomical and Space Technology Center at the Korea Astronomy and Space Science Institute. said.
On the other hand, tempered glass is still mainly used for refracting telescope lenses. Plastic materials are also used in small lenses. Unlike reflective telescopes that reflect external electromagnetic waves, refracting telescopes have to refract and pass electromagnetic waves, so there are many factors to consider, such as color, penetrating power, and uniformity of the lens. It is technically difficult to increase the size of the lens, and it is even heavier than a reflector, so most space telescopes are manufactured with reflectors.
An image of the Southern Ring Nebula captured by the James Webb Space Telescope. Courtesy of NASA
Is the next-generation telescope a water droplet?
On April 1, the National Aeronautics and Space Administration (NASA) announced that the Fluid Telescope Experiment (FLUTE) team had successfully completed land and air tests. FLUTE is a project jointly conducted by Israel Technion Israel Institute of Technology and NASA, and the goal is to secure the technology to make a giant lens by solidifying a liquid polymer in outer space.
The biggest advantage of a fluid telescope is that it does not require grinding or polishing. These processes are one of the processes necessary for making the lenses and reflectors used in telescopes, and they prevent diffuse reflection and irregular refraction by making the surfaces of the lenses and reflectors made in the frame smooth. Senior Researcher Kim said, “In order for the telescope to perform properly, the surface roughness must be less than 2 nm (nanometer, 1 nm is one billionth of a meter). It is an important technology for making telescopes,” he said.
On the other hand, a fluid forms a perfect sphere by surface tension in outer space. Surface tension is a force acting in a direction that minimizes the surface area of a fluid. As the sphere has the smallest surface area in the same volume, it is calculated that a lens with a smooth surface can be obtained without a separate process. Moran Berkovich, a professor at Technion Israel Institute of Technology, said, “Physical phenomena occurring in nature are simply means of solving complex processes.” Thanks to this, it is possible to manufacture ultra-large lenses with dimensions of several tens to hundreds of meters, which have been difficult to implement with conventional technology.
There are also limitations that need to be overcome. When a perfect spherical surface is used, spherical aberration occurs in which the focus is not focused in one place. In order to overcome this limitation in real telescopes, aspherical lenses and reflectors are mainly used. Senior Researcher Kim said, “It remains to be seen how additional processing is performed on lenses made through fluid telescope technology to minimize spherical aberration and realize aspherical lenses.”
Fluid telescopes take advantage of the properties of matter to form a perfect sphere with surface tension in zero gravity. However, in the spherical lens that can be made in this way, spherical aberration occurs because the refractive index is different and the focus is not focused. Science Donga DB
The era of telescope making in space
Another reason NASA is challenging the development of fluid telescopes is that they can develop telescopes directly in outer space. No matter how light and smooth a telescope is, if it is built on Earth, it will have to be launched into space at great cost. A huge cost is also required to prevent vibrations and shocks that occur while being loaded into the rocket and passing through the atmosphere. On the other hand, if you make your own lens in space, it is a calculation that can save money.
A full-scale fluid telescope experiment in outer space will be conducted through the first civilian space mission, Axiom-1. Axiom missions include building a civil space station and manufacturing goods in microgravity situations. Difficult manufacturing techniques can be implemented on Earth, such as when there is little gravity, no sedimentation of the mixture occurs, and purer protein crystals can be obtained. It is an experiment to create a kind of space factory.
A researcher holds a lens made from the Fluid Telescope Experiment (FLUTE). After the ground and air tests, additional tests in space are planned. Provided by Technion Israel Institute of Technology
Space factories are also paying attention to private companies. In the age of space exploration, which is becoming more active in the age of new space, it is necessary to develop a space factory to supply goods with less cost and shorter time. In 2019, Jeff Bezos, who heads the private space company Blue Origin, announced plans to build a heavy industry factory in space, saying, “We will leave the earth as a residence and produce goods needed in space in space.”
There are other technologies that can make telescopes in outer space, such as fluid telescopes. This is 3D printing technology. NASA and the Korea Astronomy and Space Science Institute are in the process of conducting research. Senior Researcher Kim said, “Using 3D printing technology, telescope parts can be manufactured at any time in space.
An image of the space station to be built for the Axiom mission. The technology needed for the space factory will be developed here. Provided by axiom space
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