But Walker realized the real benefits of a spherical, inflatable telescope would be found in space. Traditional radio telescopes use parabolic dishes as reflectors, which gather radiation and focus it on a specific point. While this works well enough, astronomers have to move the entire dish to point it a specific spot, which becomes a burden when the telescope is in space. With Walker’s design, you can point the telescope by moving the antenna inside the sphere, rather than repositioning the entire telescope. A spherical telescope also has a large field of view, so it can image large portions of the universe without moving.

Walker’s inflatable telescope is not the first time NASA has flirted with beach balls in space. In the early 1960s, NASA launched Echo 1 and Echo 2, which were massive inflatable reflectors that could passively bounce radio signals around the world. But no one ever applied the concept to deep space observation. (In 1996, though, NASA did undertake an experiment with an inflatable parabolic reflector in space.) After proving that the large balloon reflector worked as intended, Walker received a Phase 2 NIAC grant to design a space-based version of the inflatable telescope.

The result is the Terahertz Space Telescope, an inflatable ball 40 meters in diameter with a steerable antenna inside. Because gas pressure in space is so low, Walker says you could inflate the massive telescope using less gas—likely nitrogen or neon, due to its low freezing temperature—than you’d need to inflate a party balloon on Earth. Obviously space debris and micrometeoroids are a concern for inflatable objects in orbit, but Walker says if one were to hit the balloon, the slow diffusion of gas in the telescope means that it would still take years before the telescope deflated.

The effective diameter of the Terahertz Space Telescope, Walker says, would be about 25 meters. To put this in perspective, the James Webb Space Telescope—which is slated to launch in 2021, and will be the most sensitive telescope ever sent to space—has an aperture of about 6.5 meters. The price difference is even more dramatic: Walker estimates the inflatable telescope would cost around $200 million to send to orbit, whereas the James Webb telescope is expected to cost about $10 billion by the time it’s launched.

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But Walker's telescope still needs to get built. If it can overcome that hurdle, the Terahertz Space Telescope could observe the universe using wavelengths that would allow it to detect the presence of water in deep space. It could help locate water-rich asteroids within our solar system, or help detect water in the habitable zones of other solar systems. Walker is particularly excited about the prospect of detecting gaseous water near the stars in protoplanetary systems, which he says could tell us a great deal about how Earth came to be covered in water.

For now, though, the Terahertz Space Telescope has only undergone two small experimental tests. Both tests were conducted under the auspices of Freefall Aerospace, a company Walker cofounded as a spinoff of his work on inflatable telescopes. Freefall aims to use inflatable satellites similar in design to the beach ball telescope to beam 5G to Earth. Last year, a prototype of one of these inflatable satellites hitched a ride to the stratosphere on a NASA high-altitude balloon, and perfectly demonstrated its antenna-steering technology. Shortly thereafter, Walker began working on a design to create a constellation of inflatable satellites and got two prototypes to “talk” to one another on the ground.

Next, Walker expects to deploy an inflatable 5G satellite in orbit attached to a cubesat. He is also working on two NASA proposals to send the large balloon reflector to the stratosphere and the Terahertz Space Telescope to orbit. Recently, Walker and his colleagues even pitched NASA on a space-based array made out of these inflatables, which would allow them to image the surface of exoplanets around Alpha Centauri, our closest stellar neighbor. Yet as with all things in space science, securing the funding for the mission will be almost as difficult as developing the technology. With any luck, we may be hunting for habitable exoplanets using giant inflatable telescopes in the not-so-near future.

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