A quadcopter that can fly like an aerial drone, but also splash down into water and operate like a submersible, could be used for search and rescue missions or engineering inspections.
at the Chinese University of Hong Kong and his colleagues created a prototype device called Mirs-X, which weighs 1.63 kilograms and is 38 centimetres wide. It can hover for 6 minutes in the air or dive underwater for around 40 minutes. Mirs-X is waterproof at depths of up to 3 metres and moves at up to 2 metres per second in water.
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Its propellers spin rapidly to create lift in the air, but because water is much more dense, they have to turn much more slowly underwater. This is achieved by a dual-speed gearbox for each motor.
In air, the drone manoeuvres by altering the speed of its propellers to tilt the craft. But in water, this is much less effective, so the machine is fitted with rotating mounts that can tip the motor and propeller in different directions to create sideways thrust.
Chen says that future, larger versions of the device could be helpful for search and rescue operations, observing from high altitude and then descending into the water for a closer look, or for carrying out engineering inspections of bridges and tunnels.
鈥淎t the moment, it鈥檚 just a prototype. It鈥檚 easy for us to do this [scale of test] because we can do that in a swimming pool, but if we scale up, we鈥檒l have to do it in the sea or a river,鈥� he says. 鈥淚f we want it to have some real applications for industry, we really need to scale the platform. You need a longer endurance; you need a bit more payload.鈥�
The researchers intend to create a larger version of the prototype that is around 2 metres across, equipped with sonar and cameras. They also hope to fit it with hardware that will allow the drone to grasp objects it finds underwater and carry them. But greater amounts of waterproofing would require a trade-off with ability, according to the team.
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