Some drones fly; other drones swim.  Is it possible for a single drone to do both?

Several Chinese companies are currently in the forefront of developing drones that can launch from the water and become airborne or plunge into the watery depths from the sky.

These “transmedium” drones could one day revolutionize the way Unmanned aerial vehicles (UAV’s) are deployed, industry observers say.

Last November, Asia Times reported that Chinese researchers from Harbin Engineering University had unveiled two transmedium prototype submarine drones dubbed “Longbow 1” and “Longbow 2”  Each can carry a 1-kilogram payload and dive to 100 meters underwater.

The main difference between the two models is their basic configuration.  Longbow 1 is a fixed-wing drone while Longbow 2 features a folding wing design.  Both have a maximum speed of 75 mph.

Tests of each prototype were conducted at Long Fengshan Reservoir in Wuchang last October.   The two drones – sometimes referred to as “flying submarines”  — swam underwater for about 40 seconds, after which they surfaced and flew autonomously for several minutes.

The tests revealed that the Longbow 2’s folding wing design was problematic, largely due to flight stability issues.  When the drone re-surfaced, it was unable to consistently launch from the water once it unfolded its wings.

Harbin researchers conducted nine separate modifications to the folding wing design to try to correct the problem.  They also introduced a special air bag to allow the drone to float on the water’s surface before preparing to launch

While these modifications were largely successful, Longbow 1 is likely to become the preferred prototype moving forward, researchers say.

Researchers at Shanghai institute are also experimenting with flying submarines, but in this case, the basic design is a quadcopter.  The drone, dubbed “TJ-Flying Fish,” is equipped with a dual propulsion system that adjusts to each medium.  It weighs just 3.6 pounds and is capable of hovering in the air for six minutes or swimming underwater for about 40 minutes.

Industry experts say that China’s transmedium drones are likely being developed primarily for their military applications.  The ability of the drones to dive underwater could allow them to evade missile attacks, while also giving them the ability to encroach on missile defenses. Larger transmedium drones might eventually be equipped with torpedoes, analysts say.

For their part, Shanghai designers are emphasizing the civilian uses of their transmedium drones, including resource exploration, search and rescue and infrastructure inspections.

The idea for flying submarines is not entirely new.  Back in 2008, the US Navy, with funding from DARPA, began testing prototypes designed for attacks on enemy vessels.  The crafts would fly close to the target, then dive underwater to avoid enemy radar.  If detected by sonar, they could resurface and become airborne again to deliver their payload.

But those gas-powered flying submarines also had pilots aboard.

Outside of China, transmedium drones are considered “dual use,” with the civilian applications dominating the design process. The drones are also designed to be battery-powered and fully autonomous, which makes them safer and more efficient as well as more sustainable.

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