I telescopi su palloncini potrebbero essere un gioco

When you think of innovative new space launch concepts, you likely think of rockets like SpaceX’s Starship or NASA’s Space Launch System carrying telescopes or robotic explorers out into orbit and beyond. And certainly, rockets are here to stay, remaining the principal way of carrying things beyond Earth’s gravity. However, an alternative and cheaper option might come from a much older form of technology: Balloons.

• Su su e via
• A new kind of balloon

Contenuti

• Su su e via
• A new kind of balloon
• A telescope lofted by a balloon
• How to fly a telescope strapped to a balloon
• SuperBIT and beyond

Balloons filled with hot air or gas have been lofted up into the skies for centuries, with records of the ancient Chinese military using balloons for signaling as far back as the 3rd century AD, and crewed balloon flight beginning in Europe in the 1780s. And they have been used in astronomy research as well, like the U.S.’s Project Stargazer of the 1960s which sent two men and a telescope 82,000 feet (25 kilometers) into the air in a high-altitude balloon to observe the stars.

Now, recent developments in balloon technology from NASA mean balloons may once again prove their worth for cutting-edge astronomy projects, carrying high-tech telescopes up into the atmosphere from where they can observe the cosmos. We spoke to one of the researchers working on a new generation of balloon-based telescopes, Mohamed Shaaban of the University of Toronto, to learn how this old technology is being put to brand new use.

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To understand why balloons have such great potential for use in telescope missions, you need to understand why we send telescopes into orbit to begin with. While there are plenty of telescopes located on the ground doing sterling work, if you want to look at really distant objects then you need to account for the problems caused by Earth’s atmosphere.

The big issue is the water vapor in the atmosphere, which blurs images taken by ground-based telescopes. That’s why telescopes are often placed in locations that are very dry and at very high altitudes, like Mauna Kea in Hawai’i or the Atacama desert in Chile. But the best solution is to look at distant objects from above the atmosphere, hence why telescopes like Hubble are put into orbit.

Traditionally, if you want to put a telescope above the atmosphere, then you send it into orbit on a rocket. That’s expensive and not easy to do — and it’s hugely expensive to fix any problems which occur and require hardware replacement — but it’s a highly reliable method for avoiding Earth’s atmosphere.

Balloons, on the other hand, have been used in scientific research for decades, typically over Antarctica. The problem with using balloons for telescopes before now has been a matter of light. Most scientific balloons are launched in Antarctica because the research hardware is generally powered by solar panels, which can only operate during daylight hours, and Antarctica has 24-hour daylight during its summer. But that means you’re limited to the kind of research that can be done during the day, which isn’t great for telescopes.

But the newly developed balloons from NASA, called super-pressure balloons, can operate in Earth’s mid-latitude region and work during both day and night cycles. “For the first time we’ll be able to do night-time science [with balloons],” says Shaaban, which opens the door to enabling a whole range of astronomy projects.

A new kind of balloon

There are big advantages to balloons as a method to carry telescopes. Firstly, launching a balloon is tremendously cheaper than launching a rocket. Also, you can very easily bring a telescope back to Earth and then relaunch it, so if you have to perform any maintenance then it’s relatively easy. That’s a big deal when you consider how difficult and complex it was to perform maintenance on the Hubble telescope when it experienced hardware problems shortly after its launch in 1990.

“With ballooning, the beauty of it is that you have recoverable launches,” Shabaan said. “So you launch the system multiple times. So you put something together, and it doesn’t have to work the first time – because you’re going to launch it for a single night to test it, then bring it down and reiterate. So you don’t need the very aggressive testing structure that you need for orbital [missions].”

It’s this complex testing that drives up the price of orbital missions. Making sure every piece of hardware works right out of the gate, that everything has multiple redundancies, and all these redundancies work with each other too — this is what can send the budgets for space projects soaring.

With ballooning, it’s easier to iterate and adjust hardware design as you go along. And if you send a balloon high enough into the edges of the atmosphere, you get almost all the water vapor-reduction advantages of being in orbit.