Mahesh Krishnaswamy is the head of manufacturing at Project Loon and has seen several revisions of balloon shapes and sizes over the life of the project. The current balloon envelopes are 15 meters wide and 12 meters tall, created from sheets of polyethylene. As of late 2015 the balloons built and tested by Project Loon are flying 100+ days before coming down. A parachute is also built into the system in the event that the controlled gas venting system is lowering a used balloon too quickly.
Balloons are built at room temperature but the operating conditions at 65,000 feet can be as low as -60 degrees Celsius. Testing in different conditions or testing fabric instead of a fully fabricated balloon gave incomplete data to Project Loon's engineers. They found that partnering with McKinley Climatic Laboratory helped to understand the strain that the balloon material would face in the stratosphere. Simulating day and night cycles allowed for tests and data collection, and this video also shows a balloon tested to rupture.
Mahesh goes on to discuss manufacturing methods that have been adapted to make Loon builds faster and more repeatable. Bringing in quality control and multi-operation machinery has allowed two workers to create balloons that used to take dozens of workers. This is just one example of how an idea that seemed radical in 2013 is now being implemented and examined from several angles.
Project Loon's goal is still to bring internet to the whole world. Using solar panels and onboard antennae each balloon communicates with the balloon network and stationary antennae on the ground. After pilot testing in June 2013 in New Zealand, Loon has expanded into Brazil and hopes to create a ring of constant connectivity at some latitudes in the Southern Hemisphere.
Here at ENGINEERING.com we've written about Project Loon before, and it's exciting to see that Google is still keeping resources and manpower focused on the project. Loon's main page has a lot of Google-designed information, with videos about the balloon's longevity , controlling the balloon , the antenna , and several more components and systems. A Google+ post written just before the New Year presented the Golden Balloon Awards, and celebrated the progress made in the last year. The fastest launch was completed in 29 minutes, the farthest traveling balloon went 113,000 kilometers in one flight, and two balloons drifted 100 kilometers apart while still transmitting data.