Project Loon: Beaming Internet From Stratospheric Balloons

Project Loon was a plan to give internet to remote places using balloons. The balloons floated in the stratosphere, far above planes and weather. Each one worked like a cell tower in the sky.

Loon was a wireless communication project. It had nothing to do with waste, solar power or water.

Who started it?

• Google X, Google’s research lab for “moonshots”, unveiled Loon in June 2013.
• The first tests began in August 2011 in California’s Central Valley.
• Google X’s Rich DeVaul had the key idea, called variable buoyancy. It means steering balloons by changing their altitude.
• In 2018 Loon became an independent business inside Alphabet.

What was the goal?

X said Loon began with one question. Could balloons bring affordable internet to the “last billion” people? These are the last unconnected communities and those least able to pay.

X says Loon aimed at rural areas, coverage gaps and places hit by disasters.

How high did the balloons fly?

Loon sent its balloons to about 60,000 feet. That is roughly 18 km. At that height they sit above aircraft, birds and weather.

What should you remember?

• Loon was balloon-based, not satellite-based.
• It was run by X, then by an independent Alphabet company.
• It closed in 2021.

A Loon balloon was a plastic balloon the size of a tennis court. It had to survive for hundreds of days in a very harsh place.

What is the stratosphere like?

• Winds there can reach 100 km per hour.
• Temperatures can fall to minus 90 degrees Celsius.
• A balloon can feel temperature swings of about 150 degrees Celsius.

What kind of balloon was it?

Loon used superpressure balloons. This is the term in the Nature paper on Loon’s flight control.

A superpressure balloon is sealed and made of material that does not stretch. Heat from the sun changes the pressure inside, but not the volume. So the balloon keeps floating at about the same height.

What was it made of?

X says each balloon was made of polyethylene. Workers cut the film and seamed it in a pumpkin shape. A hole just a millimetre wide could end a flight early.

How long did one balloon last?

• In 2020 a balloon named HBAL703 flew for 312 days.
• It launched from Puerto Rico in May 2019 and flew on to Peru.
• It then circled the globe and settled over the Pacific.
• It landed in Baja, Mexico, in March 2020.
• Loon’s CTO said the record showed that its work to make balloons last longer was paying off.

What kept it healthy?

Automated systems tracked the lift gas and adjusted ballast during the flight. This protected the film as sunshine raised the pressure. At night the navigation system chose altitudes that kept the balloon warm enough to stay pressurised.

What else did the balloon carry?

• Solar panels powered the equipment by day and charged batteries for the night.
• An avionics unit worked as the balloon’s brain.
• A parachute brought the balloon down in a controlled way at the end.

Loon balloons came back to Earth. Weather balloons are hardly ever recovered. Loon could study the old balloons and make the next ones better.

Loon balloons had no propulsion. They steered by choosing which wind to ride. X calls this “sailing” the winds.

Why does this work?

Winds in the stratosphere come in layers. A layer at one height may blow in a different direction or speed from the layer just above. A balloon that can rise or sink can pick the layer that blows its way.

How did the balloon rise and sink?

• Each balloon held a smaller inner balloon called the ballonet.
• Changing the airflow into the ballonet changed the balloon’s altitude.
• A new altitude meant a new wind layer, and so a new direction.

How did Loon know which wind to pick?

Loon built predictive models to make interactive maps of the sky. The maps showed wind speed and direction at set heights, times and places. Smart algorithms then chose the best flight path through the layers.

With this method balloons sailed thousands of kilometres. Small groups could also cluster over one region.

What did machine learning add?

On 2 December 2020 Nature published a paper on Loon’s flight controller. It was built with reinforcement learning. It kept Loon balloons on station at several places, including a 39-day experiment over the Pacific Ocean.

The paper says the controller outperformed Loon’s previous algorithm. The Register quotes Loon’s CTO. He said that, as far as Loon knew, this was the first use of reinforcement learning in a production aerospace system.

What is station keeping?

Station keeping means staying near one chosen spot. A fleet system sent each balloon to a place. A navigation controller brought it close. Then the station-keeping controller took over.

The balloons passed signals from one to another and down to people. A telecom company on the ground still sold the service.

What was the network design?

• A ground station linked to the internet sent signals up to a balloon.
• Balloons relayed the signal to each other, like a mesh network in the sky.
• Balloons near users beamed LTE (4G) signals down to ordinary phones.

What jobs did one balloon do?

In Kenya a balloon could do three jobs. It could serve users. It could act as a link that passed the internet to other balloons. Or it could move back toward the service area.

Other balloons waited nearby for their turn to enter the service area.

How wide was the coverage?

• In 2015 Google said one balloon covered a ground area about 40 km across.
• By 2020 Loon said its footprint was over 11,000 square kilometres.
• Loon said that is about 200 times the area of an average cell tower.

Who sold the service?

Loon did not sell internet directly. It partnered with telecom companies to share cellular spectrum. Google India’s managing director, Rajan Anandan, said in 2016 that a Loon pilot needs a local telco. In Kenya the partner was Telkom Kenya.

What did laser links add?

Loon tested lasers to send data between balloons. These links carried more than 20 gigabits per second. The same idea lives on in Project Taara, which uses light beams to carry data.

Loon moved from lab tests to real service between 2013 and 2020. Its own history names five main places.

What is the timeline?

• June 2013: New Zealand farmers were among the first people to connect through a stratospheric balloon.
• 2014: Loon beamed an LTE link to a school classroom in Brazil.
• 2017: Floods in Peru and Hurricane Maria in Puerto Rico wrecked ground networks. Loon sent balloons and gave emergency links to hundreds of thousands of people.
• 2018: Loon became an independent Alphabet business.
• July 2020: Loon began service in Kenya for Telkom Kenya subscribers.

What happened in Kenya?

The first service area covered nearly 50,000 square kilometres in western and central Kenya. Loon planned a fleet of around 35 or more balloons. A test in late June 2020 showed 18.9 Mbps download and 19 ms delay.

X called it the first non-emergency, large-scale use of Loon. It also called it the first balloon-powered internet in Africa.

What is the HAPS Alliance?

Loon’s team co-founded the HAPS Alliance in 2020. X says it aims to speed up innovation and connectivity work in the stratosphere.

Alphabet announced the closure on 21 January 2021, US time. The blog post by X head Astro Teller is dated 22 January 2021.

What reason did Alphabet give?

Astro Teller of X wrote this. “The road to commercial viability has proven much longer and riskier than hoped.” The stated reason was commercial viability, not a failed balloon. The team had already flown a balloon for 312 days.

Was the technology a failure?

Teller listed the team’s feats. They steered balloons precisely in the stratosphere. They built a mesh network in the sky. They also built balloons that survived the harsh stratosphere for long flights.

SpaceNews noted that Loon was seen as both complementary to, and competitive with, satellite networks.

What happened after the announcement?

• Most of the Loon team moved to other roles at X, Google and Alphabet.
• A small group stayed to wind down operations, including the Kenya pilot service.
• Alphabet pledged $10 million for connectivity, entrepreneurship and education groups in Kenya.
• The team published The Loon Collection, an archive of insights for future stratospheric work.

What lives on?

Some Loon technology, such as the fast optical links, lives on in Project Taara. X says Taara works with partners in Sub-Saharan Africa, starting in Kenya.

India discussed a Loon pilot in 2015 and 2016. Loon’s own history lists New Zealand, Brazil, Puerto Rico, Peru and Kenya. India is not on that list.

What did the government say in December 2015?

On 11 December 2015 the Telecom Minister gave a written reply in the Rajya Sabha. He said the band Loon proposed to use is used for cellular operations in India. He said it would interfere with cellular transmissions.

Reports said Loon needed spectrum in the 700 to 900 MHz band. Telecom companies already used that band.

Did India agree to a pilot?

• MediaNama, citing the Economic Times, reported in December 2015 that the government had given an in-principle nod to a pilot.
• The Economic Times also reported that the Minister proposed a partnership with BSNL, the state-run telecom company.
• In February 2016 The Register reported that the government asked Google to pick a local carrier.
• In March 2016 Google India’s managing director said Google could not run a pilot without a local telco.
• TechCrunch noted an Economic Times report that the government had raised technical and security concerns.

What does India do now?

India has moved to other stratospheric and satellite options. Three are in the official record.

• Satellite internet licences: the Telecom Department issued GMPCS licences to OneWeb India, Jio Satellite Communications and Starlink Satellite Communications. A Rajya Sabha reply on 29 January 2026 said so. Amazon Kuiper’s application was under examination.
• Satellite spectrum rules: TRAI released recommendations on 9 May 2025 on spectrum for satellite services. DoT had cited the Telecommunications Act, 2023.
• Stratospheric airship: DRDO flew its first Stratospheric Airship Platform on 3 May 2025 from Sheopur, Madhya Pradesh. It reached about 17 km and flew for about 62 minutes.

Why does the airship matter?

DRDO says it is a step toward lighter-than-air platforms that stay up at stratospheric heights for very long periods. Loon’s CTO also described Loon’s craft as more like a balloon-based high-altitude platform.

UPSC Prelims 2016, GS Paper I, Q35 (Series A), asked a one-line question.

What was the question?

“‘Project Loon’, sometimes seen in the news, is related to”

• (a) waste management technology
• (b) wireless communication technology
• (c) solar power production technology
• (d) water conservation technology

The official key for Series A gives (b).

Why are the other options wrong?

• Loon was about carrying internet signals, not waste, solar farms or water.
• Solar panels on each balloon only powered its own equipment.
• Loon moved signals through the air, so it is wireless communication.
• All three wrong options sound like common tech topics. That is the trap.

How do you answer it fast?

Remember the picture. Balloons float at 60,000 feet and beam LTE signals to phones. That is internet by radio, so only option (b) fits.