Multi-Kilometer Space Telescopes and Megameter Arrays

Rigidized polymers appear to be a feasible technology to create space telescopes larger than kilometer sizes. It should be possible to make 50 meter space telescope elements in 1000 kilometer baseline space telescope arrays.

The Event Horizon Telescope at 1.3 millimeter wavelength achieved 25 microarcsecond resolution on M87.
Many 50-meter space telescopes in a 1000 kilometer baseline array would 100 times better with 245 nanoarcsecond resolution using 1 micron wavelengths.

Making arrays of 40 or 50-meter space telescopes over a 1000 kilometer baseline would be better for imaging exo-earths (earth planets in other solar systems) and blackholes. They would also likely be cheaper to make than a kilometer space telescope.

The 1000 kilometer baseline arrays would have over 400,000 times the light collection of the Hubble Space telescope.

The six image above show the increases in image quality so that we can go from binary stars being a single point of light to seeing the two stars as separate points and then to more and more detail of the surface of the star.

50-meter space telescopes should be easily made from mylar inflation. Mylar inflation likely tops out at 100-meter space telescopes.

Larger monolithic inflated UV-cured solid apertures are theoretically possible up to 100 kilometers in size but we will need more space launch capabilities. They could be built after we have fully rapidly reusable launch capability.

Phased arrays of apertures are unlimited in aperture size.

They have a design with two concentric spheres and other optics to get diffraction limited space telescopes. Diffraction limited space telescopes are the resolution limit of regular physics.

There have been other work to exceed the diffraction limit but those have not been developed with this kind of size scaling. The diffraction limit designs are only for the large monolith space telescopes.

The telescope arrays are light buckets and do not try to push for the diffraction limit. They will be used for different kinds of imaging.

13 thoughts on “Multi-Kilometer Space Telescopes and Megameter Arrays”

  1. Even better is using the sun itself as a lens. Unfortunately that doesn’t become effective until a focal point 500AU from the sun…

  2. That is David Kipping’s terrascope idea. You can see his video on the cool worlds youtube channel. Definitely worth a few experiments to see if the idea works.

  3. You can not use a transparent material, it has to be highly reflective to work as a mirror. Even if you start with a transparent polymer, you then need to silver it somehow before you can use it as a telescope.

  4. Those guys “envision” an assumingly perfectly rigid, perfectly shaped, optical-grade sperical surface with a kilometer diameter. It is not going to happen, not even in Star Trek scenario.

    You can estimate the weight of that thickness at that scale. If it is notionally very light 1kg per square meter, a hemisphere mass would be over 500 tons. And at thickness to diameter ratio 0.1/1000, it is still a soap bubble, even if it is made of diamond. If it is made of any polymer, it would be more likened to a wiff of smoke than a structure: no strength, no shape, no integrity.

    I will skip the rest of it. Put some numbers on those fantasies, and you will see them for what they are. Engineering is numbers.

  5. I think the structure can be many cm thick. Like I said, it doesn’t need to be light. “Thin film” is an unnecessary assumption.

    Most of the structure can be removed after the initial sphere shape is formed, so it doesn’t get in the way of the optical path. The rest can be reinforced with a much stronger and more rigid non-polymer structure. For that matter, the polymer can be treated as just a sacrificial mold that won’t even be present in the final structure.

    Station-keeping would obviously need to be multi-point, and take into account the acoustic behavior of the structure. Not easy, but doesn’t seem impossible either.

    But I’m more in favor of active modular structures than any sort of monolithic behemoths.

  6. Strangelove makes a very-valid point regarding the flimsiness of a humungous space structure, made up ultimately of … soap-bubble-thick film. The Solar Wind, apart from anything else, is highly chaotic.  

    It might be nice of that authors of this article were professional … or even amateur … telescope makers. They’d very probably be a whole lot less sanguine regarding feasibility of 1000 km scale telescopes in space.  

    I’m absolutely NOT saying it cannot be done.  

    But amongst the various problems, just figuring a hyperbola or parabolic section with the sub-wavelength-of-passband is a profound task when using thin films. Better would be to use a corrugated formed surface; think fractals… large scale backing corrugations are trusses, smaller scale are welded (plastics, glasses, metals) materials akin to cross-ply cardboard, but way stepped up. For the front surface, increasingly fine foams, not made of plastic, but aerogels and sintered ceramics.  Finally, the front surface, again plausibly aerogel of the denser type.  

    It could be figured (AKA “ground and polished”) to sub-wavelength accuracy over sub-kilometer to maybe kilometer scales.  Chosen judiciously, near-zero-temperature-coefficient could also be achieved, super-critical for space operations.  

    Still … the idea then of arraying hundreds-to-thousands of these giant scopes into a larger synthetic aperture gigascope … still seems to have solar-wind chaotic buffeting problems. Hard ones.  GG

  7. There is no such thing as a transparent material in full spectrum sunlight. Organics absorb infrared, and one-sided heating makes thrust that moves fairly large asteroids around the system.
    Protective layers must have depth to be protective. A few micrometers of anything will protect from nothing.
    All polymers are damaged by full-spectrum UV. Plasma and UV will damage most optical materials, definitely all transparent materials, and absolutely all polymers – implanted protons reduce covalent compounds, electrons build up charge in dielectrics, energetic electrons change molecular structres (used in industry for cross-linking polymers), and vacuum UV (200nm or less) photons’ energy exceeds band gap even in good dielectrics.
    Station keeping for a vast zero-strength structure with optical surface is impossible. Imagine station-keeping for kilometer-scale soap buble in the wind.
    Both separately and in combination, these are insurmountable engineering problems, because academics were not interested in engineering aspect of their fantasies. “Paper reactors” never change.

  8. A transparent material shouldn’t be affected much by solar pressure (though no material is 100% transparent to the entire spectrum). There are ways to provide station-keeping. And polymers certainly can be coated with protective layers. Besides, not all polymers are equally susceptible to UV. Unlike light sails, these things need not be light nor thin at all, as long as they still allow the relevant parts of the spectrum to reach the optics. All of these sound like surmountable engineering problems.

  9. Acedemics are at it again. A huge polymer sphere will be torn to shreds rather quickly, as academics do not bother considering that space is not empty at all. Aside from little speedy dust, space is also full of light that exerts so much pressure that makes fairly large rocks change orbits. One can only wonder which effect will be the first to blow away that silly contraption: damage from debris, or thrust from solar light. Then there is solar plasma that will etch that thin polymer into dust very quickly. Solar arrays are mostly protected from that by a glass layer that absorbs the low-energy part of plasma and most of UV spectrum. As no such layer is “feasible” on a thin polymer, it will be full spectrum plasma and full spectrum UV versus feeble organic molecular bonds. Plasma will win, but material science and even physics is too boring for academics pondering on the fine details of a star surface 49 light years away. My goodness, they never change.

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