What do you picture when you think of a drone? A solitary, remote-controlled toy with propellers, or perhaps a large, unmanned military aircraft? Soon, those images could be quite different: drones are becoming smaller, cheaper to make, can zoom around on their own, and gather in groups of hundreds, even thousands, to fly like a flock of birds.
They’re called swarms – get enough of them together, and they could outpace humans in many ways; they could save your life, or they could be a deadly collaborative force on the battlefield.
Why do drone swarms matter?
For starters, on the battlefield they could outperform weapons and technology that militaries have used for decades. Think about it: in a congested city, teams of tiny quadrotors could buzz around to gather intelligence. Tank battalions could be overrun by miniature attack drones diving in from all directions at once. At sea, thousands of small drones could sweep in to attack a warship; many might be shot down, but others might make it through, destroying radar and leaving the ship defenceless.
A drone swarm can lose dozens of members and keep going
Plus there is no leader or commander in a swarm; the swarm is a self-organising system in which all the elements are equal. Swarming allows drones to search an area efficiently, or fly together without colliding. And only one operator is needed to control the whole swarm.
Swarms are tough. One missile can bring down an aircraft, but a swarm can lose dozens of members and keep going. Air defences with a limited supply of missiles can be overwhelmed by enough opponents.
But drones will soon be swarming in many other situations too, from rock concerts to barnyards.
So I could start seeing swarms of drones in everyday life?
Indeed. In fact, you probably already have.
Earlier this year, 300 drones assembled into an American flag in Lady Gaga’s Super Bowl halftime show, illuminating the night sky. And Intel is promoting their Shooting Star swarms as an alternative to fireworks. Chinese company eHang claimed the record for the biggest swarm, in a spectacular New Year show in which 1,000 drones formed a map of China and the Chinese character for 'blessings'.
Swarms could also check pipelines, chimneys, power lines and industrial plants cheaply and easily.
Drone swarms may even have a place on the farm. They can spot plant disease and help manage water use, or spray pesticides and herbicides only in the exact spot needed, all working cooperatively to cover the area and fill in gaps.
Nikolaos Papanikolopoulos of the Centre for Distributed Robotics at the University of Minnesota is working on solar-powered drones that will ultimately work together to survey large swathes of farmland at low cost.
“Their roles may include early detection of nitrogen deficiency, plant disease, and proper management of water resources,” says Papanikolopoulos.
While drones have been used in rescue operations for years, dispatching swarms of tinier versions could save even more lives.
The University of Delft’s Micro-Air Vehicle Laboratory are developing a swarm of ‘pocket drones’, each small enough to fit in your hand. They fly indoors, in buildings too badly damaged for human rescuers to investigate, and will spread out to search for survivors in the aftermath of earthquakes and other disasters.
Researchers at Loughborough University has built a system to help with mountain search and rescue which uses a team of up to 10 small, hand-launched drones. The drones are equipped with thermal cameras to easily locate lost climbers, and by communicating with each other they ensure that the entire area is covered.
Which militaries are developing swarms – and why?
There’s more than one superpower pursuing swarm technology.
The US, for example, recently launched 103 small ‘Perdix’ drones from F/A-18 jets. These weigh a few hundred grams, and are released from dispensers normally used for flares. The 3D-printed Perdix drones are disposable, and are intended to suppress enemy air defences by acting as decoys or jammers or by locating radar so they can be destroyed.
The US Navy also aims to develop a swarm of drones that costs less than a missile. It’s developing software that allows sub-swarms to be split off for particular missions, or fresh drones to join the swarm seamlessly.
Another player is China, long the leader in small consumer drones. Chinese company DJI alone has around 70% of the global market, and now the Chinese military is seeing what they can do with this new technology. At an aerospace exhibition in December, state-owned China Electronics Technology Group Corporation (CETC) displayed a video of nearly 70 drones flying together. The drones flew in formation and collaborated in an intelligence-gathering mission. Those drones could also cooperate in a ‘saturation attack’ on an enemy missile launcher. They all dive in to attack simultaneously from different directions – far too many at once for the defenders to stop.
Perhaps the most ambitious plan is the US Marine Corps’ project for a range of drones for use on land, sea and air. These might be the first wave to hit the beach ahead of the humans, scouting, locating enemy positions, and possibly attacking them. The swarm may also provide defence against swarms of enemy drones. To explore this angle, the Corps is setting up swarm-versus-swarm wargames. (There have already been drones designed to capture other drones.)
These little drones could be spies, scouts, or intel-gatherers, too. The Defense Advanced Research Projects Agency (Darpa), the Pentagon’s advanced science agency, envisages foot soldiers having their own swarm for reconnaissance, especially in urban areas and inside buildings.
"Two hundred and fifty small air vehicles have to occupy six city blocks,” says Stephen Crampton of Swarm Systems. The swarms could potentially “self-organise in sub-swarms to deliver useful information, such as 'tell us about threats to our position'.”
They all dive in to attack simultaneously from different directions – far too many at once for the defenders to stop
So, what does the future hold for swarming drones?
Swarming drone technology is still very much in their infancy. But it’s evolving fast.
In theory, swarms can defeat any existing weapon, and can deliver enough precision firepower to cause destruction on a massive scale. Their impact could rival the development of the machine-gun: anyone without their own drone swarm faces rapid defeat on the battlefield. Warfare may then become simply a matter of who has the biggest and best drone swarms.
But the battlefield is far from the only place we could see swarms. In fact, they could one day live alongside us.
In the long term, if researchers at Harvard’s Wyss Institute are right, then small swarming drones might become as much a part of our environment as insects. Their RoboBee project is developing tiny drones smaller than a paper clip and weighing a tenth of a gram. Thousands of RoboBees could be used for weather monitoring, surveillance – or even crop pollination as the number of honey bees declines.
Keep an eye out for flocks of the tiny bots everywhere. After all – they’ve found fans in everyone from farmers to Lady Gaga.
Join 800,000+ Future fans by liking us on Facebook, or follow us on Twitter.
If you liked this story, sign up for the weekly bbc.com features newsletter, called “If You Only Read 6 Things This Week”. A handpicked selection of stories from BBC Future, Earth, Culture, Capital, and Travel, delivered to your inbox every Friday.