UP, UP and away! High-altitude balloons called Stratollites might soon be giving the US military and NASA permanent and relatively low-cost eyes in the sky over any part of the planet they want.
Developed by US firm World View, Stratollites are uncrewed helium-filled balloons that tour the stratosphere at between 10 and 46 kilometres up, with cameras and sensors on board. As the wind in each layer of the stratosphere blows in a different direction, a Stratollite鈥檚 path can be changed simply by moving to a different height and hitching a ride. The balloons are controlled from the ground.
World View has used dozens of flights to refine the computer models and algorithms used to move the balloons. Along the way, the company claims to have carried out the biggest controlled altitude-change manoeuvre ever by a balloon, switching nearly 8 kilometres in one sweep.
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The firm aims to have balloons that can permanently linger over a very small spot, by continually adjusting their height, with on-board solar arrays providing all the power they will need. 鈥淢ultiple times we鈥檝e demonstrated the ability to stay within a very tight radial area 鈥� under 50-kilometre radius for over 24 hours,鈥� says Andrew Antonio, World View鈥檚 director of marketing.
The firm released images from one Stratollite this month with a resolution of half a metre. This is enough to distinguish a pickup truck from a car, and is comparable to high-quality commercial satellite imagery.
Current spy satellites revisit a given point less than once a day, but a Stratollite can theoretically keep watch 24/7. It will also be cheaper: Antonio says that a one-month Stratollite mission will cost hundreds of thousands of dollars, compared with millions for a satellite.
鈥淲e think this has the potential to be a game changer for us,鈥� says US admiral Kurt Tidd, commander of US Southern Command, which handles US military operations in Central and South America and the Caribbean.
鈥淚mages taken from the Stratollite are detailed enough to distinguish a pickup truck from a car鈥�
Southern Command has been testing Stratollites since last August, and is interested in using them for combating drug trafficking and piracy in remote areas, something it currently uses drones for. Once deployed, Stratollites and drones can both be spotted from the ground by a keen observer, but whereas drones are noisy, Stratollites are silent.
NASA is also testing the balloons. The agency has operated stratospheric balloons for decades to monitor everything from Earth鈥檚 surface to cosmic rays, but once the balloons are in the sky, the direction of travel isn鈥檛 controllable. Alan Stern, who leads NASA鈥檚 New Horizons mission, which completed a fly-by of Pluto last year, is a co-founder of World View.
Alphabet, Google鈥檚 parent organisation, has its own stratospheric balloon project called Project Loon. It plans to use the balloons to provide mobile communication in remote areas. Last year the company deployed balloons to provide mobile phone communications in Puerto Rico after Hurricane Maria destroyed infrastructure.
Steering Stratollites isn鈥檛 always going to be easy, however. In some places winds may blow predominantly in one direction, says Neal Butchart at the UK Met Office鈥檚 Hadley Centre. 鈥淪uccess is likely to vary with the latitude band and hemisphere the balloon is flying in,鈥� he says.
Balloon mania through the ages
1670 Francesco Lana de Terzi, an Italian priest, designs a 鈥渇lying ship鈥� lifted by four copper spheres with all the air sucked out, making them lighter than air. Unfortunately, for the spheres not to collapse they would need to be so thick that the ship would be too heavy to take off.
1783 The first successful crewed balloon flight takes off from the Palace of Versailles in France. Two years later Jean-Pierre Blanchard crosses the channel from England to France in a balloon filled with hydrogen that has flapping wings for propulsion. The journey takes two and a half hours.
1937 Moments before landing, the Hindenburg airship bursts into flames. Thirty-six people die and public confidence in hydrogen-filled airships disintegrates.
2018 Airships are rarely used for transport, but are still inflated for geological surveys, filming events and advertising. More uses, such as Google鈥檚 Project Loon, are on their way (see main story).
This article appeared in print under the headline 鈥淪py balloons for catching pirates鈥�
Article amended on 26 January 2018
Correction:聽We have amended this article to clarify what gas the balloons are filled with.聽
