It’s an exciting time for astronomers and cosmologists. Ago James Webb Space Telescope (JWST), astronomers have been treated to the sharpest and most detailed images of the universe ever taken. webPowerful infrared imagers, spectrometers, and coronal imaging devices will allow much more to come in the near future, including everything from surveys of the early universe to direct imaging studies of exoplanets. Furthermore, many next-generation telescopes will go into operation in the coming years with 30-meter (~98.5 ft) primary mirrors, adaptive optics, spectrometers, and spectrophotometers.
Even with these impressive instruments, astronomers and cosmologists are looking forward to an era when more advanced and powerful telescopes will be available. For example, Zachary Cordero
of the Massachusetts Institute of Technology (MIT) recently proposed a telescope with 100 m (328 ft) primary mirror They will be built independently in space and bent into shape by electrostatic actuators. His proposal was one of the many concepts he chose this year Advanced Innovative NASA Concepts NIAC Phase I Development Program.
Corder is the Boeing Career Development Professor in Aeronautics and Astronautics at MIT and a member of the Aviation Materials and Structures Lab (AMSL) and Small Satellite Center. His research integrates his expertise in process science, mechanics, and design to develop new materials and structures for emerging aerospace applications. His proposal is the result of a collaboration with Professor Jeffrey Lang (from MIT’s Electronics and the Microsystems Technology Laboratories) and a team of three students with AMSL, including a Ph.D. student Harsh Jirishbhai Bundia.
Their proposed telescope addresses a major problem with space telescopes and other large payloads being packed for launch and then deployed into orbit. In short, trade-offs in size and surface resolution limit deployable space telescopes to 10 meters in diameter. Consider the recently launched version James Webb Space Telescope (JWST), the largest and most powerful telescope ever sent into space. To accommodate the payload fairing (on top of the Ariane 5 rocket), the telescope was designed so that it could fold into a more compact shape.
This included the primary mirror, secondary mirror, and sun shield, all of which unfolded once the space telescope entered orbit. Meanwhile, the primary mirror (the most complex and powerful of all) is 6.5 meters (21 ft) in diameter. Its successor, the Ultraviolet/Optical/Infrared Surveyor (LUVOIR), will contain a similar collapsible array and a primary mirror measuring 8 to 15 m (26.5 to 49 ft) in diameter – depending on the specific design (LUVOIR-A or -B). As Bhundiya explained to Universe Today via email:
Today, most spacecraft antennas are deployed in orbit (for example, Northrop Grumman’s Astromesh antenna) and are optimized for high performance and gain. However, they have limitations: 1) They are passive deployable systems. That is, once deployed, you cannot Adaptively changing antenna shape 2) they become harder to kill as they get larger 3) they exhibit a trade-off between diameter and resolution i.e. their accuracy decreases as their size increases, which is challenging to achieve astronomy and sensing applications that require large diameters and high resolution (such as JWST ).
While several construction methods in space have been proposed to overcome these limitations, detailed analyzes of their performance for building microstructures (such as large-diameter reflectors) are lacking. For their proposal, Cordero and colleagues performed a system-wide quantitative comparison of materials and processes for manufacturing in space. Ultimately, they determined that this limitation could be overcome by using advanced materials and a new space-based manufacturing method called Bend-Forming.
This technique, invented by researchers at AMSL and described in A The last paper Co-authored by Bhundiya and Cordero, it is based on a mixture of Computer numerical control (CNC) high-performance hierarchical deformation and material processing. As Harsh explained it:
Bending forming is a process for manufacturing 3D wire frame structures from metal wire feedstocks. It works by bending a single strand of wire at specific nodes and at specific angles, and adding joins to the nodes to form a rigid structure. So to manufacture a specific structure, you turn it into bending instructions which can be carried out on a machine such as a CNC wire bender to be fabricated from a single strand of raw material.The main application of Bend-Forming is in the fabrication of the supporting structure for a large antenna in orbit.The process is well suited to this application because it is low in power, and can manufacture structures with similar compression ratios high, and basically has no size limit.”
Unlike other assembly and fabrication methods in space, the bending forming process is low in energy and is uniquely enabled by the extremely low temperature environment of space. In addition, this technology enables smart structures that take advantage of multifunctional materials to achieve novel combinations of size, mass, rigidity, and precision. In addition, the resulting intelligent structures take advantage of multifunctional materials to achieve unprecedented combinations of size, mass, rigidity, and precision, breaking design paradigms that limit traditional truss or tension-compatible space structures.
In addition to their native precision, large structures with a curvilinear profile can use their electrostatic actuators to define a reflective surface with sub-millimeter precision. This, Harsh said, will increase the accuracy of the artificial antenna in orbit:
The active control method is called electrostatic actuation and uses the forces generated by electrostatic attraction to precisely shape a metal grid into a curved shape that acts as a reflector for the antenna. We do this by applying a voltage between the grid and a “driving surface” that consists of a shape-bending support structure and deployable electrodes. By tuning this potentiometer, we can precisely shape the surface of the reflector and achieve a high gain, parabolic antenna.”
Harsh and colleagues conclude that this technology will allow a diffusible mirror with a diameter of more than 100 m (328 ft) that can achieve a surface resolution of 100 m/m and a specific area of more than 10 m.2/ kg. This capability will surpass existing microwave radiometric technology and could lead to significant improvements in storm forecasts and better understanding of atmospheric processes such as the hydrological cycle. This will have major implications for Earth and exoplanet observation studies.
The team recently demonstrated a 1-meter (3.3-foot) prototype of an electrostatic inverter with a bending support structure at the 2023 American Institute of Aeronautics and Astronautics (AIAA). SciTech Conference, which ran from January 23 to 27 at National Harbor, Maryland. With this first phase of the NIAC grant, the team plans to mature the technology with the ultimate goal of creating a reflector to measure microwave radiation.
Looking into the future, the team plans to investigate how to use Bend-Forming in geostationary orbit (GEO) to create a microwave radiometric reflector with a field of view of 15 kilometers (9.3 miles), a ground resolution of 35 kilometers (21.75 miles) and a proposed. Frequency range 50 to 56 GHz – Ultra High Frequency and Extreme High Frequency (SHF / EHF) range. This will enable the telescope to retrieve temperature profiles from exoplanets’ atmospheres, a key property that allows astrobiologists to measure habitability.
“Our goal now with NIAC is to work on implementing our bending forming and electrostatic actuation technology in space,” Harsh said. “We envision manufacturing 100-meter diameter antennas in geostationary orbit with a curved support structure and electrostatically reflective surfaces. These antennas will enable a new generation of spacecraft with increased sensing, communications and power capabilities.”
Further reading: NASA