NASA's next-gen space telescopes could dwarf Webb. By using liquid lenses?

They could even "eliminate the effect of gravity".
Brad Bergan
An illustration of a hypothetical liquid lens telescope.Studio Ella Maru / NASA  

Is bigger, better?

It depends on whether you like the cosmos or not.

But when it comes to looking at it with a telescope, larger telescopes are an easy win, since they can gather more light, enabling astronomers to see farther into deep space, observe unconscionably distant objects, and ultimately build a more cohesive and accurate picture of the physical universe.

An experiment stowed aboard the forthcoming Axiom-1 mission bound for the International Space Station (ISS) will evaluate the basics of constructing a space telescope that uses a liquid mirror. Despite how bizarre that sounds, the behavior of fluids in space is promising enough to tease at the future of astronomy, multiplying the size of telescopes 10, or even 100 fold, according to a blog post from NASA.

In other words, the future of astronomy could begin this week.

Liquid lenses could be the future of space-based telescopes

Every liquid possesses an elastic force of cohesion that can create the placid surface with which we're familiar. This is how some insects can glide effortlessly across liquid surfaces, and it's also why raindrops have a specific shape. The force of surface tension is so strong that when water droplets are 2 mm or smaller, they retain a spherical shape.

Sadly, any larger than this and droplets are squished under their own weight. But this isn't so in space.

Under the microgravity of outer space, blobs of water and other liquids will eventually take on a near-perfect spherical shape. And it looks really cool.

NASA Bubble Space
NASA Astronaut Karen Nyberg staring at us through a floating, spherical bubble of liquid, in microgravity. Source: NASA

Microgravity yields interesting shapes to liquid lenses

Principle Investigator Edward Balaban of NASA's Fluidic Telescope Experiment (FLUTE) at Ames Research Center, California, joined with scientists at the agency's Goddard Space Flight Center in Greenbelt, Maryland, in addition to the Israeli Institue of Technology's Technion to evaluate whether high-precision lenses and mirrors could be constructed via liquids.

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"We thought, why not take advantage of the way liquids naturally behave in microgravity and apply it to the construction of large-scale telescopes or space-manufactured optical components that can have all kinds of uses," explained Balaban in the NASA blog post.

"In microgravity, liquids take on shapes that are useful for making lenses and mirrors, so if we make them in space, they could be used to build telescopes that are dramatically bigger than was previously thought possible."

But before this new means of scanning the stars can be lofted into space, the inter-agency team plans to execute crucial tests on Earth. "Liquids are useful not only for creating the lenses themselves, but also as a mechanism to eliminate the effect of gravity in an experiment on Earth," said Associate Professor Moran Bercovici at Technion, in the post.

Liquid lenses will be tested on the ISS

"By injecting a liquid that can be solidified, into circular frames submerged in water, we were able to create lenses literally in a janitor's bucket," explained Valeri Frumkin, another scientist who worked on the method used by Bercovici's team. "Polymers, which are also used in nail salons to make acrylic nails or in adhesives like superglue, are a natural choice for lens material."

"The trick is to make sure that the water has the exact same density as the polymer we're injecting so that the forces of buoyancy precisely oppose gravitational forces to simulate the conditions of weightlessness," added Frumkin. Two zero-gravity parabolic flights provided the opportunity to test the team's ideas in December 2021 — resulting in 50 iterations of 15- to 20-second periods of microgravity.

This was enough time for the teams to create liquid lenses, and, "[s]ure enough, in a few seconds we were able to create a free-standing liquid lens — until the plane lifted upwards again and gravity kicked in," and synthetic oils used for a liquid began to "ooze out," said Bercovici. But with the forthcoming experiments on the ISS, the teams expect to create smooth and perfectly shaped surfaces — in effect, developing the perfect mirrors for the future of space-based telescopes, and astronomy itself.

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