It's been two years since Google first disclosed Project Loon, and while the company continues to keep most details of the project secret, the technology and challenges behind it are slowly coming into focus.
Loon is an ambitious attempt to bring the Internet to the roughly 5 billion people on the planet who are out of range of existing networks. The project involves suspending cellular access points under high-altitude balloons to provide Internet access to those on the ground, an idea that sounds elegantly simple but was anything but.
A series of recent presentations and talks by Google X employees have revealed some of the technical and commercial challenges the company faced in realizing Loon, and in nearing its target cost of $10,000 per balloon.
The balloons travel in air currents at an altitude of around 60,000 feet. That's close enough to Earth to maintain a direct connection to smartphones but high enough to avoid aircraft. It's also in a part of the atmosphere criss-crossed by high-altitude winds, so Google can steer the balloons by moving them up and down to catch air currents moving in different directions.
But at that altitude, the balloon and the electronics are battling frigid temperatures of around -65 degrees Celsius.
Batteries and other components don't work well in the cold, so all the electronics sit in a large Styrofoam-insulated container to keep them warm. Most are kept switched on even when they're not needed, so the components stay warm. Perhaps counter-intuitively, that means better battery life, because bringing cold components back to life requires more energy than just leaving them ticking over.
The cold also makes the nylon the balloons are made from turn brittle and causes lubricants to break down -- challenges to Google's goal of keeping each balloon in the air for at least 100 days. The balloons are bathed in strong ultra-violet and cosmic radiation, adding to the challenges, and endure extreme pressure changes as the helium inside expands and contracts as the balloons float in and out of sunlight.
When Loon was first announced, high-altitude balloons typically could stay aloft for no more than a couple of days before puncturing, and some thought Google's endurance goal was crazy. But the company is now regularly meeting its 100 day target, and one balloon stayed aloft for 187 days.
For the communications, the initial plan was to send proprietary Wi-Fi signals to fixed antennas on the ground, but that was soon switched to cellular LTE signals. This brought the advantage of being able to deliver a signal directly to a smartphone, and means Loon can operate in a part of the spectrum with much less interference than the Wi-Fi bands.
Sign up for CIO Asia eNewsletters.