Balloons are headed to Puerto Rico to provide cellular communication service to the Caribbean island. Around 82 percent of the island's communications infrastructure was damaged by Hurricane Maria in September.

The U.S. Federal Communications Commission granted a temporary license to Google to deploy the experimental high-altitude balloons, called Project Loon. The balloons are made by the Aerostar Division of Raven Industries, based in Sioux Falls, S.D.

The solar-powered balloons relay cell signals down from about 12 miles above the ground.

Raven was founded in 1956 as a designer and manufacturer of high-altitude research balloons for the American space program.

Project Loon balloons are designed and manufactured to survive the conditions in the stratosphere. Made from sheets of polyethylene, each tennis-court-sized balloon is built to last more than 100 days before returning to the ground in a controlled descent.

Project Loon took components of a cell tower and redesigned them to be light enough and durable enough to be carried by a balloon into the stratosphere. All the equipment is powered entirely by renewable energy, with solar panels powering daytime operations and charging a battery for use during the night.

Project Loon balloons travel approximately 20 km above the Earth's surface in the stratosphere, well above airplanes, wildlife and weather events. In the stratosphere, winds are stratified, and each layer of wind varies in speed and direction.

To get balloons to where they need to go, Project Loon uses predictive models of the winds and decision-making algorithms to move each balloon up or down into a layer of wind blowing in the right direction. By moving with the wind, the balloons can be arranged to provide coverage where it’s needed.

Custom-built Autolaunchers are designed to launch Loon balloons. Huge side panels provide protection from the wind as the balloon is filled and lifted into launch position. The crane is pointed downwind to release the balloon. Each crane is capable of filling and launching a new balloon every 30 minutes.