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It may not come as a surprise to hear balloon technology hasn't moved on much since the 1950s, after all, we've been mostly jetting about in aircraft and spacecraft since then; but that has caused Google a few headaches when it came to developing super balloons for Project Loon, its ambitious plan to bring the Internet to remote spots around the world. The problems it faced where highlighted by Google X's Astro Teller, who spoke at the recent Solid Conference in San Francisco.

Teller said balloon design was one of the five key development challenges of Project Loon, and getting it right was far harder than originally anticipated. Most balloons, he told conference attendees during his keynote, kept expanding until they went bang -- not very helpful -- while materials which didn't ending up tearing. Again, not an ideal situation for something that need to remain in the air. When a design that did work was hit upon, Teller said it proved very difficult to steer.

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To illustrate how many designs Project Loon has had since the beginning, the team named each prototype after a bird, and began -- in traditional Google style -- at the beginning of the alphabet with Auk. "We've made it all the way to Nighthawk, or N," Teller's quoted as saying, Which tells you how many ideas we've tried."

Manufacturers involved with the project wanted to look into balloon design, and some promised they could lower the per-balloon cost by three-quarters once they hit on a solution. But if the balloons were still not suitable, then cost was the least of the team's problems..

It's the second time in several weeks that Teller has talked about Project Loon and its challenges. During Google I/O, he said "We knew we had a lot to learn, but we misestimated how much we had to learn." For example, the balloons are so large, they have to be stood on by engineers, and tests were carried out to see which socks caused fewer leaks. Fluffy ones, apparently, worked best.

The research and perseverance has paid off. Project Loon's balloons now stay in the air for six months, then steered around the world and positioned to within 500 yards of the intended target area. That's way beyond the 100-day minimum flight time estimates, that Google says will make Project Loon a viable solution to provide Internet to the billions of people who cannot get it using traditional means.