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Editor’s note: This blog was originally published by the Loon team on April 21, 2020. In 2021, Loon's journey came to an end. The Loon team have shared their flight data and technical, operational and scientific insights in The Loon Collection to support the next generation of stratospheric innovation. Thank you to everyone who supported the Loon team along the way.
Loon balloons are currently drifting over Kenya performing network testing, and preparing to bring connectivity to people who subscribe to mobile service with our partner Telkom Kenya. While folks are often fascinated with our high altitude platforms hovering 20km in the stratosphere where they provide Internet service¹, I find equally fascinating the journey each balloon takes to the people it connects.
All Loon flights begin at one of our two launch sites in Puerto Rico or Nevada. Our launch team loads the flight system onto a special cart that plugs into our launch system (pictured above). The launch system has three wind walls and can be rotated so the opening where the balloon drifts out always faces downwind, ensuring the balloon is always sheltered from the elements. A custom apparatus fills the balloon with lift gas inside the launch system.Our highly skilled teams of onsite operators and the flight engineers (in our flight operations centers) work together to perform a long list of preflight checks, coordinate with air traffic control, and ensure the launch can proceed safely. The mechanical and software systems assist the team to conduct the launch process in a very repeatable, very safe way. That allows us to both scale to a large number of launches and also to reduce process variability among those launches. This is one of the keys to ensuring our flights fly for hundreds of days.
A Loon flight ascending into the stratosphere
After the familiar² back and forth coordination messages on our launch channels, the balloon is released and ascends into the stratosphere. Once at float, Nairobi is around 11 thousand kilometers from Puerto Rico as the crow flies, but our balloons do not fly in a straight line. Instead, they fly the fastest route that drifting on the stratospheric winds allows.
To determine that route our software automation builds a map. Numerical weather forecasts are built throughout the day by weather centers around the world, and we assimilate the outputs of those models to create an ever-changing global estimate of how long it takes to reach our destination, Kenya, from everywhere in the stratosphere. The example map below shows a snapshot in time: places that are closer to Kenya are dark blue, and places that are quite far away are red. Using this snapshot as an example, if a balloon were in the red area southwest of Australia, it would take a long time to get to Kenya. However, if it were in the blue area off the east coast of South America, the journey would be much faster.
A snapshot in time of a map that Loon's automated navigation system uses to bring balloons to Kenya.
Loon balloons follow the map. Our navigation system analyzes the winds around each balloon every minute to ensure that, compared against the map, they are always moving closer to Kenya. Over time, these small steps result in successful journeys spanning thousands of kilometers.
For example, HBAL125 (pictured below) launched from Puerto Rico and traveled over the Atlantic Ocean, flying southeast along the coast of Brazil. It flew south into the Southern Atlantic jet stream to quickly round the Cape of Good Hope before heading back north into the slower winds of the equatorial region³. At this point, the balloon took a planned detour for Loon to collect data about the stratospheric winds over the Indian Ocean to enhance to our models in the region⁴. Finally, in coordination with the local authorities, HBAL125 flew into Kenyan airspace to begin network testing two weeks ago.
The flight path of HBAL125 on its way from Puerto Rico to Kenya
The winds aloft change every day so, like snowflakes, no two journeys will ever be exactly the same. Other balloons heading for Kenya will fly over central Africa, and still others will fly west out of Puerto Rico and reach their destination after a trans-Pacific flight. The balloons optimize for safety first, and travel time second.
In addition to assimilating winds (forecasts and real time observations) and computing efficient trajectories, our fleet management system autonomously monitors the weather, reasons about how to avoid harm if an unlikely problem arises, and processes a large amount of telemetry every minute to ensure everything is working as intended. Prioritizing safety in our operations, and everything else we do on Loon, is a key ingredient in the recipe that has given us the longevity to fly 1+ million hours and continually grow our operations as we scale the number of people we are connecting.
Once we arrive in Kenya, our flights follow a carefully choreographed dance, again, with our fleet management system’s machine learning-driven navigation algorithms coordinating all the movements. The balloons perform a variety of maneuvers to maximize the number of people they are able to connect throughout the day. The plot below shows the flight paths of 4 balloons over 24 hours working together in Kenya airspace. The colors on the trajectory line represent the altitudes of the flights, and demonstrate how the navigation system keeps them constantly moving up and down to achieve their mission.
Changing altitudes of four balloons along their paths over Kenya for a day.
The Loon team is excited to bring service to people in places that previously had little or no connectivity in Kenya. As I’ve often said, people have much more important needs than the Internet — if you can bring folks food, clean water, or medical supplies, do that first.But as humanity copes with the covid19 pandemic and we find ourselves physically distancing from our friends, colleagues, and family, it is our ability to stay in touch online that is keeping us informed, together, and connected.Now more than ever, the divide between people who can get online in their home and those that service doesn’t quite reach is apparent, and the importance of making it possible for everyone to have access to the Internet has never been so clear in our day to day lives.It is with this spirit that the Loon team continues our work to bring our network online in Kenya as quickly as we can, and to continue to work towards our mission to connect people everywhere.
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¹ Folks take to Twitter to share a photograph of a “UFO”, from time to time.
² What is now familiar to me after many years on Loon observing launches.
³ This path highlights the value of Loon’s automated flight routing technology. Humans would often prioritize a distance that is shorter in kilometers traveled, but takes a longer time. For a balloon drifting on the winds, often a big detour is the fastest way from A to B.
⁴ Data from over a million hours of flight through the stratosphere allows us to build models of the winds and weather that help us improve our navigation system.