How NASA’s Liquid Lenses Could Revolutionize Space Exploration

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Over the years we have become incredibly good at making telescopes. Just look at the 6.5m (21ft 4in) wide James Webb Space Telescope or the aging but still excellent 4.5m (14ft) wide Hubble Space Telescope. These powerful devices help us peer deeply into the cosmos and unravel some of the deepest mysteries of the universe.

However, NASA recently tested technology that could make a space telescope so large that it dwarfs anything that has come before it. Welcome to the amazing world of liquid lenses!

Eyes in the sky: Optical lenses and mirrors are surprisingly complex creations. They must be precisely shaped to function. We can easily do this for smaller lenses like your glasses, as your eyes are not very sensitive to blemishes.

But for the massive and powerful lenses and optical mirrors of large telescopes, the slightest imperfection is enough to render them useless. Take the Webb telescope: for its mirrors to work, it has to be so precise that if you scale the mirror to the same size as the United States, the the largest bump is said to be only two inches tall.

To obtain such a perfect shape, it is necessary years of complex polishing, grinding and checking. We find it incredibly difficult to create the perfect parabolic curves needed for these optical parts. There is no one-step production method. It is an extremely long, arduous and expensive process.

JWST folded for transport. Credit: NASA

To make matters worse, such huge telescopes are impractical to use on Earth because our atmosphere gets involved. It’s one of the reasons Hubble and Webb are in space.

However, that means these massive telescopes also have to fit in a rocket. To accommodate the Webb’s gigantic primary mirror, it had to be split into hexagonal sections, allowing it to be folded up and fit inside a rocket. It must then be carefully aligned, in space, at a distance, with nanometric precision. Otherwise, it won’t work.

This size restriction further increases development time, cost, and the possibility of failure, thanks to complex folding mechanics and separate mirrors that must function as one.

Beyond Gravity: NASA is working on a solution. Why not make mirrors in the space using liquid dynamics, rather than building hard lenses and mirrors on Earth?

Unlike our manufacturing methods, liquids can easily form perfect parabolic curves. If you look through a drop of water just before it falls from the faucet, you can see it acting like a lens. This is due to surface tension pulling on the droplet, forcing it into a nearly perfect curved shape.

The problem is that gravity on Earth is strong enough to distort this natural parabolic manufacturing process. It can be used to make small lenses or parabolic mirrors, but not large perfect ones.

However, that’s a different story in the microgravity environment of space. Up there, it’s theoretically possible to use liquids to create perfect giant lenses or parabolic mirrors.

liquid lens

Water creating a spherical lens in microgravity. Credit: NASA

How?

Well, you are using a liquid polymer that can be fixed (frozen) by UV light. An undisturbed drop of this liquid will form a perfect sphere in microgravity. If we take a drop like that and spin it, it will puff up and form an ideal parabolic lens. Then all you have to do is blast it with UV, and you’ll have a solid, usable lens!

You can even modify this method and use reflective polymers or coatings to create the parabolic optical mirrors found in giant telescopes.

Using this process, it is theoretically possible to build telescopes and other optical equipment orders of magnitude larger than the Webb in a fraction of the time and at a fraction of the cost.

liquid lens

FLUTE running in the ISS. Credit: Axiom Space

Test the theory: from NASA Fluidic Telescope Experiment (FLUTE) has been recently undertaken on the ISS to take this amazing technology from theory to practice. They attempted to create small optical lenses from floating polymer liquids and analyze their accuracy.

The results are yet to be published, but if FLUTE was successful, it’s a sign that we could build optical systems in a space ten times larger than the Webb, unlocking staggering advances.

First, giant telescopes help us understand some of the deepest mysteries of the universe. They can peer into our universe’s deep past, helping us solve some of physics’ greatest mysteries, like dark matter. They can even analyze the composition of exoplanets in search of extraterrestrial life.

But one liquid lens telescope several times the size of the Webb could see much deeper into the cosmos and at much greater levels of detail. Such a telescope could be the tool that finds new life or radically changes physics. And maybe we can finally build it without needing a trillion dollars.

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